Hard color-singlet exchange in dijet events in proton-proton collisions at \sqrt{s} = 13 TeV
EEUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
TOTEM
CERN-EP-2020-2292021/02/16
CMS-SMP-19-006TOTEM-2021-001
Hard color-singlet exchange in dijet events inproton-proton collisions at √ s =
13 TeV
The CMS and TOTEM Collaborations * Abstract
Events where the two leading jets are separated by a pseudorapidity interval devoidof particle activity, known as jet-gap-jet events, are studied in proton-proton collisionsat √ s =
13 TeV. The signature is expected from hard color-singlet exchange. Each ofthe highest transverse momentum ( p T ) jets must have p jetT >
40 GeV and pseudorapid-ity 1.4 < | η jet | < η jet1 η jet2 <
0, where jet1 and jet2 are the leading and sub-leading jets in p T , respectively. The analysis is based on data collected by the CMS andTOTEM experiments during a low luminosity, high- β ∗ run at the CERN LHC in 2015,with an integrated luminosity of 0.66 pb − . Events with a low number of charged par-ticles with p T > | η | < f CSE , is measured as a function of p jet2T , the pseudorapidity dif-ference between the two leading jets, and the azimuthal angular separation betweenthe two leading jets. The fraction f CSE has values of 0.6–1.0%. The results are com-pared with previous measurements and with predictions from perturbative quantumchromodynamics. In addition, the first study of jet-gap-jet events detected in associa-tion with an intact proton using a subsample of events with an integrated luminosityof 0.40 pb − is presented. The intact protons are detected with the Roman pot detec-tors of the TOTEM experiment. The f CSE in this sample is 2.91 ± + − (syst)times larger than that for inclusive dijet production in dijets with similar kinematics. Submitted to Physical Review D © 2021 CERN for the benefit of the CMS Collaboration. CC-BY-4.0 license * See Appendix A for the list of collaboration members a r X i v : . [ h e p - e x ] F e b Quantum chromodynamics (QCD) is the established theory of strong interactions and it is es-pecially successful at very short distances, where physical observables can be computed in aperturbative expansion in powers of the strong coupling, α S . However, there remain cornersof phase space where predictions from perturbative QCD (pQCD) have yet to be confirmed.One such kinematic region is the high-energy limit of strong interactions, which is particularlyimportant for better understanding the initial state in hadronic collisions and for studies ofhigh-energy scattering [1, 2].In 2 → s (cid:29) − ˆ t (cid:29) Λ , where ˆ s is the square of the partonic center-of-mass energy, ˆ t is the square ofthe partonic four-momentum transfer, and Λ QCD is the energy scale below which QCD becomesstrongly coupled. In this limit, some powers of α S are multiplied by a large logarithm of ˆ s in theperturbative expansion, compensating for the smallness of α S (cid:28) α S ln ( ˆ s / | ˆ t | ) (cid:46) α S in the perturbative expansion [3–5], and its solutions are known up to next-to-leadinglogarithmic (NLL) accuracy [6, 7]. In dijet production, the expected onset of BFKL dynamicsis reached in configurations where the two jets are separated by a large rapidity interval. TheBFKL radiation pattern is also expected to be important in the study of parton distributionfunctions (PDFs) of hadrons [3–5]. In this context, the high-energy limit of QCD corresponds tothe regime of very small values of the parton momentum fraction x at low momentum transfer.The resummation of ln ( x ) terms to all orders in α S predicts a power-law growth of gluondensities at small x .At the CERN LHC, dedicated studies of BFKL dynamics include measurements of azimuthalangular ( φ ) decorrelations between jets in forward-backward dijet configurations [8] and crosssection measurements at large values of the rapidity difference between the jets [9, 10]. Ex-clusive vector meson production at the LHC [11–17] can be treated within the BFKL frame-work, as discussed in Refs. [18, 19]. Measurements of inclusive jet or multijet cross sectionsat different center-of-mass energies show no significant deviations from predictions based onthe Dokshitzer–Gribov–Lipatov–Altarelli–Parisi (DGLAP) evolution equations [20–22], whereparton emissions are strongly ordered in transverse momentum ( p T ), distinct from the BFKL or-dering in rapidity, over a large region of phase space [9, 10, 23–36]. State-of-the-art global PDFfits highlight the importance of including resummation of small x terms to all orders in α S to de-scribe inclusive deep inelastic scattering data collected by the DESY HERA experiments [37]. Alesson from these studies is that BFKL dynamical effects associated with multiple parton split-tings are very difficult to separate from other effects predicted by higher-order corrections inpQCD. More restrictive final-state studies, where other effects expected from pQCD are sup-pressed, may provide clearer indications of BFKL dynamics.A study of events is presented in proton-proton (pp) collisions with two jets separated by alarge pseudorapidity ( η ) interval devoid of particle activity. These are known as Mueller–Tangjets [38] or jet-gap-jet events. The jet-gap-jet events in this study are observed with the CMS de-tector. Previous studies of jet-gap-jet events have been carried out by the H1 and ZEUS Collabo-rations in dijet photoproduction in electron-proton collisions at the DESY HERA [39, 40], by theCDF and D0 Collaborations in pp collisions at center-of-mass energies √ s = t -channel hard color-singlet exchange [48– Figure 1: (Left) Schematic diagram of a jet-gap-jet event by hard color-singlet exchange in ppcollisions. The lines following the protons represent the proton breakup. (Right) Jet-gap-jetevent signature in the η - φ plane. The filled circles represent final-state particles. The shadedrectangular area between the jets denotes the interval | η | < t -channel two-gluonladder exchange between the interacting partons, as shown in Fig. 1, where the color chargecarried by the exchanged gluons cancel, leading to a suppression of particle production be-tween the final-state jets. This is known as perturbative pomeron exchange [3–5]. Color-singletexchange can occur in quark-quark, quark-gluon, and gluon-gluon scattering. Of these, gluon-gluon scattering is expected to be substantially favored as a result of the larger color chargeof gluons [49–51]. In contrast, in most collisions that lead to dijet production, the net colorcharge exchange between partons results in final-state particle production over wide intervalsof rapidity between the jets. These color-exchange dijet events are referred to in this paperas “background” events. Dynamical effects predicted by the DGLAP evolution equations arelargely suppressed in events with pseudorapidity gaps, since the predicted dijet productionrate is strongly reduced by way of a Sudakov form factor [48–51]. This factor, which accountsfor the probability of having no additional parton emissions between the hard partons, is notnecessary for BFKL pomeron exchange [38]. The ratio of jet-gap-jet yields to inclusive dijetyields is sensitive to dynamical effects predicted by the BFKL evolution equations, as first sug-gested in Ref. [38] and further studied in Refs. [52–56].The presence of soft rescattering effects between partons and the proton remnants modify thevisible cross section of jet-gap-jet events. These soft interactions can induce the productionof particles in the η interval that would otherwise be devoid of particles. This results in areduction of the number of events identified as having a jet-gap-jet signature. This reductionis parametrized using a multiplicative factor known as the rapidity gap survival probability, |S | . The survival probability is a process-dependent, nonperturbative quantity [48, 57–61]that is expected to have values of the order of |S | = Figure 2: (Left) Schematic diagram of a jet-gap-jet event by hard color-singlet exchange with anintact proton in pp collisions. The jet-gap-jet is reconstructed in the CMS detector, while the in-tact proton is detected with one of the forward proton spectrometers of the TOTEM experiment.(Right) Proton-gap-jet-gap-jet event signature in the η - φ plane. The filled circles represent final-state particles. The shaded rectangular areas denote the central gap region | η | < √ s =
13 TeV by the CMS and TOTEM experiments at the CERN LHC. These data wererecorded with special LHC optics settings, β ∗ =
90 m, where β ∗ is the betatron amplitudefunction at the interaction point [65]. Data were recorded by CMS with an integrated lumi-nosity of 0.66 pb − ; a subset of the data with 0.40 pb − was collected jointly with the TOTEMexperiment. The present analysis uses a similar event selection and central gap definition asthe previous measurement by CMS at 7 TeV [47]. Each of the two highest p T jets must have p jetT >
40 GeV and 1.4 < | η jet | < η jet1 η jet2 <
0, where jet1 and jet2 denote the leading and subleading jets in p T , respectively.The charged particle multiplicity ( N tracks ) in the interval | η | < p T >
200 MeV, is used to isolate color-singlet exchangedijet events from color-exchange dijet events. Jet-gap-jet events due to color-singlet exchangeare characterized by a sharp excess at the lowest N tracks values above the expected contributionof color-exchange dijet events. The increase in √ s to 13 TeV provides improved conditions tostudy the hard color-singlet exchange process in an unexplored region of phase space. Theincreased sample size relative to the previous analysis at 7 TeV allows finer binning in the kine-matic variables of interest and an improved precision in the determination of the fraction ofdijet events produced via hard color-singlet exchange. Furthermore, the analysis based onCMS and TOTEM data provides a first investigation of dijet events with a central gap and anintact proton. This analysis can elucidate the role of soft parton exchanges in the creation anddestruction mechanisms of pseudorapidity gaps in strong interactions [63]. The intact protonsin the analysis have a fractional momentum loss ( ξ ) of up to 20%, with values of the square ofthe four-momentum transfer at the proton vertex ( t ) in the range between − − .The paper is organized as follows. The CMS and TOTEM detectors are introduced in Section 2. The data sample used in the analysis is described in Section 3. The event selection require-ments are presented in Section 4. The central pseudorapidity gap and observable definitionsare discussed in Sections 5 and 6, respectively. Section 7 gives a description of the backgroundtreatment used in the analysis. The systematic uncertainties are detailed in Section 8. Theresults of the paper are shown in Section 9. A summary of the paper is found in Section 10.
The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diame-ter, providing a magnetic field of 3.8 T. Within the solenoid volume are a silicon pixel and striptracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintilla-tor hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Forwardcalorimeters extend the η coverage provided by the barrel and endcap detectors. Muons are de-tected in gas-ionization chambers embedded in the steel flux-return yoke outside the solenoid.The silicon tracker measures charged particles within the range | η | < < p T <
10 GeV and | η | < p T and 25–90 (45–150) µ m inthe transverse (longitudinal) impact parameter [66].The particle-flow (PF) algorithm [67] aims to reconstruct and identify each individual particle(physics-object) in an event, with an optimized combination of information from the variouselements of the CMS detector. The energy of photons is obtained from the ECAL measure-ment. The energy of electrons is determined from a combination of the electron momentumat the primary interaction vertex as determined by the tracker, the energy of the correspond-ing ECAL cluster, and the energy sum of all bremsstrahlung photons spatially compatible withoriginating from the electron track. The energy of muons is obtained from the curvature ofthe corresponding track. The energy of charged hadrons is determined from a combination oftheir momentum measured in the tracker and the matching ECAL and HCAL energy deposits,corrected for the response function of the calorimeters to hadronic showers. Finally, the energyof neutral hadrons is obtained from the corresponding corrected ECAL and HCAL energies.Tracks are reconstructed with the standard iterative algorithm of CMS [66]. To reduce themisidentification rate, tracks are required to pass standard CMS quality criteria, referred to ashigh-purity criteria. High-purity tracks satisfy requirements on the number of hits and the χ of the track-fit. The requirements are functions of the charged particle track p T and η , as well asthe number of layers with a hit. A more detailed discussion of the combinatorial track findingalgorithm and the definition of high-purity tracks is reported in Ref. [66]. The reconstructionefficiency for high-purity tracks is about 75% with p T >
200 MeV. The candidate vertex withthe largest value of summed physics-object p is taken to be the primary pp interaction vertex.In the vertex fit, each track is assigned a weight between 0 and 1, which reflects the likeli-hood that it genuinely belongs to the vertex. The number of degrees of freedom in the fit isstrongly correlated with the number of tracks arising from the interaction region, as describedin Ref. [66].The jets are clustered using the infrared- and collinear-safe anti- k T algorithm [68, 69], with adistance parameter of R = AST J ET package [69]. Thekey feature of the anti- k T algorithm is the resilience of the jet boundary with respect to soft radi-ation. This leads to cone-shaped hard jets. The jet momentum is determined as the vector sumof all particle momenta in the jet. The simulations show the CMS detector response is within5–10% of the true hadron-level momentum over a wide range of the jet p T and η . Jet energy Figure 3: Profile schematic of the CMS-TOTEM detector configuration during the 2015 run.The horizontal dashed line represents the beamline. The CMS detector is denoted by the filledcircle in the center. The intact proton(s) are transported via the accelerator magnetic fields(violet light rectangles), eventually passing through the silicon detectors housed in the Romanpots (black dark rectangles) of the TOTEM experiment. Sectors 45 and 56 are located in thepositive and negative η regions in the CMS coordinate system, respectively.corrections are derived from simulation to bring, on average, the measured jet energies to theknown energies at the generator level [70]. In situ measurements of the momentum balance indijet, photon+jet, Z+jet, and multijet events are used to correct any residual differences in thejet energy scale in data and simulation [70]. The jet energy resolution typically amounts to 15%at 10 GeV, 8% at 100 GeV, and 4% at 1 TeV. A more detailed description of the CMS detector,together with a definition of the coordinate system used and the relevant kinematic variables,is described in Ref. [71].The proton spectrometer of the TOTEM experiment consists of two sets of telescopes, knownas Roman pot (RP) stations [64] that are located close to the beamline. The arms are referred toas sectors 45 and 56 for positive and negative η , respectively. An RP that contains silicon stripdetectors can approach the LHC beam to a distance of a few millimeters without affecting theLHC operation [64]. The RPs are used to detect protons deflected at scattering angles of only afew microradians relative to the beam. During the 2015 special run, there were two RP stationsoperating in each sector located at ±
210 m and ±
220 m relative to the interaction point. Theconfiguration during 2015 is depicted in Fig. 3. The station at 210 m has one unit of RPs, whilethe station at 220 m has two units of RPs. Each unit has three RPs: one located above (“top”),one below (“bottom”), and one to one side (“horizontal”) of the LHC beam [64]. Before beingdetected, the trajectories of protons that have lost a small amount of their original momentumslightly deviate from the beam trajectory, with the deviation dependent on the momentum ofthe proton. The intact proton kinematics are reconstructed after modeling the transport of theprotons from the interaction point to the RP location [64, 72]. With the β ∗ =
90 m conditions,small horizontal displacements of the forward proton tracks at the RPs are directly proportionalto ξ . The detection of the forward protons also enables the reconstruction of t , which is relatedto the horizontal and vertical scattering angles of the proton track at the RPs [73, 74]. Theresolution in ξ is 0.008 for ξ ≈ ξ = The pp collision data used in this analysis were collected in a combined special run by the CMSand TOTEM experiments in 2015 at √ s =
13 TeV, when the LHC operated in a mode with lowprobability of overlapping pp interactions in the same bunch crossing (pileup). With β ∗ =
90 moptics at the interaction point of CMS, there were about 0.05–0.10 pileup interactions per event.Events were selected by trigger signals delivered simultaneously to the CMS and TOTEM de- tectors. The CMS orbit-counter reset signal, delivered to the TOTEM electronics at the start ofthe run, assures the time synchronization of the two experiments. The samples were combinedoffline by matching bunch crossing and orbit numbers, as in the previous CMS and TOTEMcombined run at √ s = − . The data were collected with an unprescaled inclusive dijet trigger. This triggerrequires at least two leading jets (jet1, jet2), both with p T >
32 GeV with | η | < p jet2T =
40 GeV, and is fully efficient at p jet2T >
55 GeV, as mea-sured with dijet events in a zero-bias sample collected using a random trigger in the presenceof nonempty bunch crossings. Trigger efficiency effects largely cancel in the ratio of yields ofevents with a central gap, f CSE , the main observable measured in this analysis, which is de-scribed in Section 6. Thus, no efficiency correction is applied in the analysis. A subset of eventsof the zero-bias sample that contains forward proton information collected by the TOTEM ex-periment is used for systematic checks in the analysis.
The following selection requirements are used for the study of jet-gap-jet events within inclu-sive dijet events as well as for the analysis of jet-gap-jet events with an intact proton: • Each of the two leading jets is required to have p jetT >
40 GeV. This selection max-imizes the number of dijet events considered in the analysis, while ensuring highdijet reconstruction efficiency. The phase space explored in the present analysis issimilar to that studied in the previous CMS measurement at 7 TeV [47]. There are norequirements on additional jets that may be produced in the collision. • The two leading jets are measured in opposite hemispheres of the CMS detector, η jet1 η jet2 <
0, and must have 1.4 < | η jet | < k T algorithm distance parameter R = η range thus locates thejets at least one unit of R away from the | η | < • The number of reconstructed primary vertices in the event is required to be at mostone. This requirement is used to reject residual pileup interactions. For this analy-sis, a primary vertex is kept if it has at least two degrees of freedom as defined inRef. [66]. Keeping events with no primary vertex retains forward-backward dijetconfigurations that have too few tracks to establish a primary vertex, as is likely forthe jet-gap-jet topology. • The primary vertex, if present, is required to be located within a longitudinal dis-tance of 24 cm of the nominal interaction point of CMS.There were 362 915 dijet events satisfying these selection requirements.
For the study of jet-gap-jet events with an intact proton (proton-gap-jet-gap-jet), in addition tothe dijet event selection described in Section 4.1, the following selection requirements on theprotons reconstructed in the RPs are also applied: .2 Intact proton selection • At least one proton must be detected in either sector 45 or 56 RP stations. • The proton track must cross at least two overlapping RP units (e.g., top-top, bottom-bottom), to ensure quality proton reconstruction. • The ξ reconstructed with the RP ( ξ p ( RP ) ) must have values of ξ p ( RP ) < t must have values of − < t < − . These bounds are based on acceptancestudies of the RPs. • The proton track impact location at the RP must satisfy the fiducial selection re-quirements 8 < | y ( RP ) | <
30 mm and 0 < x ( RP ) <
20 mm for vertical RPs, and | y ( RP ) | <
25 mm and 7 < x ( RP ) <
25 mm for horizontal RPs, where x ( RP ) and y ( RP ) denote the horizontal and vertical coordinates of the tracks in the plane trans-verse to the beamline at the RP. The beam position is at x ( RP ) = y ( RP ) =
0. Thisselection requirement ensures good proton reconstruction efficiency and acceptancewithin the RPs, and is based on acceptance studies of the RPs.For the final selection requirement, the main goal is the removal of beam background events,which consist mostly of dijet events paired with uncorrelated beam halo particles or protonsfrom residual pileup interactions. The beam halo is created by the interaction of beam particleswith the collimation instrumentation or with residual gas in the vacuum chamber. To suppressthese contributions, the following condition is applied: • Events must satisfy ξ p ( PF ) − ξ p ( RP ) <
0, where ξ p ( PF ) = ∑ i ( E i ± p iz ) / √ s is thefractional momentum loss of the proton calculated with the PF candidates of CMS.Here, E i and p iz are the energy and longitudinal momentum of the i -th PF candidatein the event, respectively. The positive or negative sign in the sum corresponds tothe scattered proton moving towards the positive or negative z direction in the CMScoordinate system, corresponding to the sector 45 or 56 directions, respectively. ThePF candidates considered in the analysis have | η | < ξ p ( PF ) , charged PF objects in | η | < p T >
200 MeVare considered. A minimum energy of 1.7 and 1.2 GeV is used at | η | < < | η | < < | η | < η -dependent energy thresholds were optimized based on zero-bias data collected during the same run conditions as in the dijet data sample. This followsfrom a similar procedure used in the 7 TeV single-diffractive dijet analysis by CMS [77] and the8 TeV CMS-TOTEM study on diffractive dijet production [75].Ideally, it is expected that the fractional momentum loss reconstructed with the central detectoror the forward proton detectors should be the same, i.e., ξ p ( PF ) = ξ p ( RP ) . However, becauseof reconstruction inefficiencies and acceptance limitations of the CMS detector, and the use ofenergy thresholds applied for each PF candidate reconstructed in CMS, these events satisfyinstead the inequality ξ p ( PF ) − ξ p ( RP ) <
0, i.e., the fractional momentum loss is underesti-mated by the CMS detector. Therefore, the region ξ p ( PF ) − ξ p ( RP ) > ξ p ( PF ) − ξ p ( RP ) <
0, which is subtracted from thedata, as explained in Section 7.2. The same selection requirement that targets the suppressionof beam background contributions was also used in the measurement of single-diffractive dijetproduction at √ s = There are 341 and 336 events satisfying the dijet and intact proton selection requirements insectors 45 and 56, respectively.
Jet-gap-jet events arising from color-singlet exchange cannot be identified on an event-by-eventbasis since color-exchange dijet events can also have central gaps through fluctuations in theparticle activity between the two jets. Nevertheless, the color-singlet exchange dijet process isexpected to lead to an increase in the number of dijet events at the lowest particle multiplicitiesover those expected to arise from color exchange.In this analysis, the charged particle activity between the two leading jets is used to character-ize the pseudorapidity gap between the jets. The multiplicity of charged particles, N tracks , isdefined as the number of reconstructed charged particle tracks between the two leading jets,where each charged particle is in the interval | η | < p T >
200 MeV. The measuredrelative p T uncertainty of each charged particle is required to be smaller than 10%; this reducesthe contribution from badly reconstructed or low-quality tracks. Reconstructed charged par-ticle tracks satisfy the high-purity criteria of CMS described in Ref. [66]. The central gap isdefined as the absence of charged particle production for | η | <
1, which is the same definitionused in the previous study at √ s = | η | < √ s . There are1650 jet-gap-jet candidate events with N tracks = N tracks =
0, events with multiplicities up to N tracks = | η | < p T thresh-olds cannot be lowered to the 200 MeV scale as with charged particle tracks. The noise level p T thresholds are 0.5 and 2 GeV for photons and neutral particles at central pseudorapidities,respectively, which leads to a looser definition of an η interval devoid of particle activity. Con-sequently, neutral hadrons and photons are not used in the definition of the central gap in thisanalysis.When an intact proton is included, the same definition of the central gap between the jetsdescribed above is used. The forward gap is inferred from the direct detection of the scatteredproton, i.e., no calorimeter-based rapidity gap is applied. A total of 11 events are found with N tracks = N tracks = N tracks ≥ p extra-jetT >
15 GeV and | η extra-jet | < Tjet1 /p Tjet2 p ) j e t T / p j e t T d ( pd N N CMS (13 TeV) -1 | < 4.7 jet1,2 h < 0, 1.4 < | jet2 h jet1 h > 40 GeV jet1,2T p = 0) tracks Data (N 3) ‡ tracks Data (N [rad] jj fD ) jj fD d ( d N N CMS (13 TeV) -1 | < 4.7 jet1,2 h < 0, 1.4 < | jet2 h jet1 h > 40 GeV jet1,2T p = 0) tracks Data (N 3) ‡ tracks Data (N extra-jets N ) e x t r a - j e t s d ( N d N N CMS (13 TeV) -1 | < 4.7 jet1,2 h < 0, 1.4 < | jet2 h jet1 h > 40 GeV jet1,2T p | < 4.7 extra-jet h > 15 GeV, | extra-jetT p = 0) tracks Data (N 3) ‡ tracks Data (N
Figure 4: Distributions of the ratio of the subleading jet to leading jet transverse momenta p jet2T / p jet1T (left panel), the azimuthal angular separation between the two leading jets ∆ φ jj (rightpanel), and the number of additional jets N extra-jets with p extra-jetT >
15 GeV (lower panel), for jet-gap-jet candidates with N tracks = | η | < N tracks ≥ | η | < Ideally, hard color-singlet exchange events should have only N tracks =
0. Occasionally, how-ever, charged particles created during the fragmentation process are produced at large angleswith respect to the jet boundary, such that they are emitted into the | η | < N tracks =
2. Theintegration interval N tracks < N tracks < N tracks < N F , the number of dijet events withno underlying color-singlet exchange with N tracks < N Fnon-CSE , and the total number of dijetevents by N . The yields N F and N are extracted directly via event counting, whereas N Fnon-CSE requires modeling of color-exchange dijet events, which is discussed in Section 7.The fraction of color-singlet exchange dijet events is given by f CSE = N F − N Fnon-CSE N , (1)and is measured as a function of kinematic variables of interest. Because f CSE is a ratio of yields,jet reconstruction uncertainties approximately cancel. The f CSE fraction can be measured as afunction of: • The pseudorapidity separation of the two leading jets, ∆ η jj ≡ | η jet1 − η jet2 | . • The subleading jet transverse momentum, p jet2T . • The azimuthal angular separation between the two leading jets, ∆ φ jj ≡ | φ jet1 − φ jet2 | .The fraction f CSE , measured as a function of ∆ η jj , is particularly sensitive to predictions basedon perturbative calculations within the BFKL framework [52–56], since it is directly relatedwith the resummation of large logarithms of energy. The fraction f CSE , as a function of p jet2T ,can be compared with phenomenology studies that predict a weak dependence of this frac-tion on p jet2T based on BFKL calculations [52–55]. This p jet2T dependence also compares betterwith previous measurements by D0 [42, 43] and CMS [47]. The fraction f CSE , as a function of ∆ φ jj , is sensitive to deviations from the back-to-back topology of jet-gap-jet events caused byhigher-order perturbative QCD corrections, e.g., those induced by higher order corrections tothe impact factors, which are related to the coupling of the perturbative pomeron to quarks andgluons [78, 79]. The f CSE is extracted in bins of the kinematic variables of interest with rangesspecified in Tables 2–4 of Section 9.For the measurement with intact protons, f CSE is the ratio of the number of proton-gap-jet-gap-jet events to the number of standard diffractive dijet events. In this case, signal events areextracted in the first two multiplicity bins, N tracks <
2. The integration region of N tracks < N tracks <
2, and on the lower mean multiplicityfound in data in events with intact protons. Because of the limited sample size, a measurementas a function of kinematic variables is not possible. Thus, the respective f CSE is extracted usingthe entire sample of events with the intact proton. Two independent, data-based techniques are used to describe the contribution of color-exchangedijet events in the lowest multiplicity bins. The first method relies on a data sample indepen-dent of the nominal sample, whereas the second method relies on a parametrization of parti-cle multiplicity distributions in hadronic collisions. These techniques avoid model-dependenttreatment of the underlying event activity, hadronization effects, and other effects that impactthe description of particle activity between the jets that are embedded in Monte Carlo events.
In the first approach, a separate N tracks distribution is obtained from a sample of events wherethe two leading jets are reconstructed on the same side of the CMS detector ( η jet1 η jet2 >
0) withjets satisfying the requirements 1.4 < | η jet | < p jetT >
40 GeV. The independent sam-ple of events where jets are produced on the same side is referred to as “SS dijet sample.” Thenominal sample, where jets are reconstructed on opposite sides of the detector ( η jet1 η jet2 < < | η | < | η | < N tracks than the OS sample.To compensate for this difference and obtain a better superposition of the N tracks distributionsof the SS and the OS dijet samples for multiplicities of N tracks >
2, the η region for the SSdijet sample is adjusted. The adjustment is estimated by matching the mean multiplicity ofthe distributions of the SS and OS samples by varying the pseudorapidity gap width in the SSsample. The optimal η interval for the SS dijet sample is | η | < √ s [44–47]. The multiplicity distribution in theSS sample is then normalized to the one of the OS dijet sample in an interval dominated bycolor-exchange dijet events, 3 ≤ N tracks ≤
40. The number of events of the SS sample inthe first multiplicity bins N tracks < < p jet2T <
50 GeV used in the analysis. An excess of OSdijet events at low multiplicities above the expected color-exchange events is observed, whichis interpreted as the contribution of hard color-singlet exchange dijet events. The f CSE fractionis observed to stabilize up to N tracks = f CSE extraction in the analysis. For eventsat low nonzero N tracks , strong correlations in η - φ between the charged particles and the jetsare observed. This suggests that events with low nonzero N tracks are due to charged particleconstituents of the jet falling into the | η | < N tracks distribution with a negative binomial distribution (NBD) function. This distributionis used to describe N tracks distributions with underlying color charge exchanges in hadroniccollisions [80, 81], as first reported by the UA5 Collaboration [82, 83] at √ s =
540 GeV. TheNBD functional form has also been used to describe pp collision data at several √ s valuesby the ALICE Collaboration [84]. The NBD function is less successful in describing the highmultiplicity tails of N tracks distributions for √ s larger than 900 GeV [83, 84], and requires the E v en t s Data, OSData, SS
CMS (13 TeV) -1 < 50 GeV jet2T
40 < p |<1) h (| tracks N - - D a t a D a t a - B k g E v en t s Data, OSNBD fit [3,35]NBD extrap. [0,2]
CMS (13 TeV) -1 < 50 GeV jet2T
40 < p |<1) h (| tracks N - - D a t a D a t a - B k g Figure 5: Charged particle multiplicity distribution N tracks in the | η | < p T >
200 MeV for opposite side (OS) dijet events satisfying η jet1 η jet2 < < p jet2T <
50 GeV. Vertical bars, which represent statistical uncertainties, are smallerthan the markers for most data points. Results from color-exchange dijet background estima-tion based on the same side (SS) dijet events and the negative binomial distribution (NBD)function fit are shown on the left and right panels, respectively. The NBD function is fit in theinterval 3 ≤ N tracks ≤
35, and extrapolated to N tracks =
0. The dashed-line arrow represents thejet-gap-jet signal region used in the analysis, N tracks ≤
2. The fraction f CSE corresponds to theratio of the excess of events at low multiplicities relative to the integrated number of events, asdescribed in the text.use of more complex phenomenological parametrizations necessary for very wide multiplicityintervals. For the study of jet-gap-jet events, a single NBD function fit is sufficient, since themain focus is at low N tracks . The NBD method for estimating the color-exchange contributionsin jet-gap-jet analyses has been used by the D0 and CMS Collaborations [41–43, 47].The NBD function is fit in the interval 3 ≤ N tracks ≤
35, which is expected to be dominated bycolor-exchange dijet events. The range of 3 ≤ N tracks ≤
35 also compares better to the 7 TeVanalysis, since the shape of the N tracks distribution is similar. The NBD function is extrapolatedto N tracks = < p jet2T <
50 GeV, used inthe analysis. As with the SS method, an excess at low N tracks over the NBD extrapolation isobserved. The fraction f CSE is observed to stabilize by integrating the excess up to N tracks = f CSE . The estimated color-exchange dijet yield in the signal region isstable with respect to variations of the starting and ending points of the fit region, as verifiedexplicitly by changing the fit interval to 3 ≤ N tracks ≤
25, 3 ≤ N tracks ≤
45, or 4 ≤ N tracks ≤ .2 Background for proton-gap-jet-gap-jet events fraction f CSE as a function of the kinematic variables of interest. It also provides for a moredirect comparison with the previous measurement by CMS at √ s = N tracks intervals. The SS method is usedfor systematic checks in the analysis. The SS method overestimates the contribution of color-exchange dijet events by about 15% relative to the results extracted with the NBD method in40 < p jet2T <
50 GeV, and by about 1–5% for larger values of p jet2T >
50 GeV. These differencesare taken as a systematic uncertainty.The performance of the NBD method is tested on the N tracks distribution of the SS dijet sampleby performing the NBD fit in the range 3 ≤ N tracks ≤
35. The extrapolation of the fit results to N tracks = p jet3T >
15 GeV and | η jet3 | < N tracks distribution of this trijet sample, further confirming the validityof the NBD approach.The f CSE fractions are extracted from the data using dijet yields uncorrected for detector effects.No unfolding of the data is necessary, since reconstruction, resolution, and migration effectscancel in the ratio of yields in f CSE . The number of color-singlet exchange dijet events in thenumerator of Eq. (1) does not depend on track reconstruction inefficiencies; the latter onlyinfluence the color-exchange dijet events in the denominator of Eq. (1), which are subtractedin the analysis. Simulation events show that the results do not change within the statisticaluncertainties if hadron-level or detector-level variables are used. This was also true for the7 TeV CMS paper [47].For these simulation studies, inclusive dijet events (with no hard color-singlet exchange con-tributions) were simulated using the leading order (LO)
PYTHIA
PYTHIA
HERWIG
HERWIG
HERWIG
IMMY package [93] is used to supple-ment MPI. A detailed simulation of the CMS detector response is performed with the G
EANT f CSE are compared with those obtained when considering thedetector response, and agree within the statistical uncertainties, provided that the signal extrac-tion is performed at most at N tracks <
3. The f CSE values in simulation are matched to those indata for these studies. For a check of the background subtraction methods used in the analysis,the f CSE values calculated with
PYTHIA - - (RP) p x (PF) - p x E v en t s / . un i t s DataBeam bkg > 40 GeV jet2T p < 0 jet2 h jet1 h | < 4.7 jet1,2 h CMS-TOTEM (13 TeV) -1 Sector 45 > 40 GeV jet2T p < 0 jet2 h jet1 h | < 4.7 jet1,2 h - - (RP) p x (PF) - p x E v en t s / . un i t s DataBeam bkg > 40 GeV jet2T p < 0 jet2 h jet1 h | < 4.7 jet1,2 h CMS-TOTEM (13 TeV) -1 Sector 56 > 40 GeV jet2T p < 0 jet2 h jet1 h | < 4.7 jet1,2 h Figure 6: Distribution of ξ p ( PF ) − ξ p ( RP ) in sectors 45 (left) and 56 (right) in data, where ξ p ( PF ) and ξ p ( RP ) denote the fractional momentum loss of the proton reconstructed with theparticle-flow (PF) candidates of CMS and the Roman pots (RP) of TOTEM, respectively. Verticalbars indicate statistical uncertainties only. The estimated background contamination (beambackground events) is represented by the filled histogram, and is estimated from the data, asdescribed in the text. No central gap is required for this plot. The dashed-line arrow representsthe requirement applied in the analysis to remove most of the beam background contribution. In the sample with intact protons, the contribution of protons from pileup interactions andbeam halo activity must be subtracted. The residual contamination that survives the selectionrequirement ξ p ( PF ) − ξ p ( RP ) <
0, as noted in Section 4.2, is estimated using an event mixingprocedure that mimics the beam background contribution in the nominal sample, as describedbelow.Events from the inclusive dijet sample are paired with uncorrelated protons from events in thezero-bias data sample. The dijet events should satisfy the same event selection requirementdescribed in Section 4. The number of events from this event mixing procedure is normalizedto data with ξ p ( PF ) − ξ p ( RP ) >
0, which is dominated by beam background events. Then,the number of events with ξ p ( PF ) − ξ p ( RP ) < N tracks from beam background, shown in Fig. 7, is determined from the event mixing procedure.Standard single-diffractive dijet events can yield a central gap between the jets by fluctuationsin N tracks , analogous to the fluctuations of color-exchange dijet events in inclusive dijet pro-duction. The methods introduced in Section 7.1 are used to estimate these contributions withmodifications that account for differences in the sample with intact protons. Generally, the N tracks is lower in events with an intact proton than in inclusive dijet production events. Forevents passing the dijet and forward proton selection requirements, the mean multiplicity inthe | η | < (cid:104) N tracks (cid:105) ≈
17, compared to the larger (cid:104) N tracks (cid:105) ≈
28 in inclusive dijetproduction. This is consistent with the overall suppression of spectator parton interactions andlower energy available for production of particles in single-diffractive events. Since the N tracks distributions in sectors 45 and 56 are similar in shape, the N tracks values from the two sectorsare summed for the analysis. .2 Background for proton-gap-jet-gap-jet events E v en t s Data, OSData, SSBeam bkg
CMS-TOTEM (13 TeV) -1 |<1) h (| tracks N - D a t a D a t a - B k g E v en t s Data, OSNBD fit [2,25]NBD extrap. [0,1]Beam bkg
CMS-TOTEM (13 TeV) -1 |<1) h (| tracks N - - D a t a D a t a - B k g Figure 7: Charged particle multiplicity distribution in the | η | < η jet1 η jet2 <
0. Vertical bars representthe statistical uncertainties. The filled histogram represents the residual beam backgroundcontamination. The contribution of standard diffractive dijet events that feature a central gap ismodeled with the same side (SS) dijet events (left) and with the negative binomial distribution(NBD) function fit (right), as described in the text. The NBD function is fit in the interval2 ≤ N tracks ≤
25, and extrapolated to N tracks =
0. The dashed-line arrow represents the region N tracks < η of the jets is notcentered at zero in single-diffractive events. This is because single-diffractive dijet events areintrinsically boosted along the beam direction, in a direction opposite to the scattered proton.Thus, in considering single-diffractive dijet events located in the same hemisphere of the CMSdetector, the N tracks in the | η | < N tracks distribution of the SS dijet sample is instead measured in intervalsof − < η < − < η < η in the data for events with an intact protonin sectors 45 and 56, which corresponds to boosts of about 0.8 units in negative and positive η ,respectively. The two leading jets are located on the same side relative to these η intervals, i.e., η jet < − η jet > η jet < − η jet > η interval, as in the constructionof the SS dijet sample of Section 7.1. The resulting N tracks distribution of the SS dijet samplematches that of the OS sample at moderate multiplicities after these adjustments. The N tracks distribution of the SS dijet sample is normalized to that of the nominal sample in the range2 ≤ N tracks ≤
40. The number of events of the SS dijet sample in the lowest multiplicity binsis then used to estimate the standard single-diffractive dijet production at low multiplicities N tracks ≤
1, as shown in Fig. 7. An excess of events over the expected background counts isobserved, which is attributed to the presence of proton-gap-jet-gap-jet events. The second approach is based on the NBD method introduced in Section 7.1. The NBD func-tion is fit in the interval 2 ≤ N tracks ≤
25, and is then extrapolated to N tracks = N tracks =
25 is chosen to include the lower mean N tracks of the dijet sample withintact protons, and, at the same time, to avoid the contribution by beam background contami-nation that dominates at high multiplicities. The NBD is fit before beam background subtrac-tion. The result is the same if the fit is carried out after the beam background subtraction, whichhas an effect on the extracted f CSE of less than 2%. An excess over the NBD extrapolation resultsis observed in the data, which provides for an interpretation in terms of proton-gap-jet-gap-jetevents. The NBD method is used to extract the main results in the analysis, which facilitates acomparison with the jet-gap-jet results extracted in inclusive dijet production. Because of thelower mean value of N tracks and the smaller width of the N tracks distribution, the NBD fit ex-trapolation is more sensitive in jet-gap-jet events with an intact proton than in inclusive dijetevents. This is quantified as part of the systematic uncertainties in the f CSE extraction.
The sources of systematic uncertainties for the f CSE fraction measurement are:
Jet energy scale:
The p T of each jet is varied with p T → p T ± δ p T ( p T , η ) , where δ p T ( p T , η ) is thejet energy scale uncertainty as a function of the jet p T and η . The new jet collection is reorderedin p T , and the analysis is repeated. The difference in the extracted fraction f CSE relative to theresults found with the nominal jet energy corrections is a measure of the associated systematicuncertainty. The resulting relative uncertainty is 0.5–6.0%.
Track quality:
The selection criteria used to define high-purity tracks are loosened and the dif-ference in f CSE with respect to the nominal selection is taken as the associated systematic un-certainty. The loose quality criteria correspond to the minimum requirements yielding well-reconstructed tracks in the CMS detector, as described in Ref. [66]. The corresponding uncer-tainty in f CSE is 1.5–8.0%.
Charged particle p T threshold: Charged particles with p T <
200 MeV are not considered in iden-tifying a central gap. To study the sensitivity of the results to this threshold, the analysis isrepeated with p T thresholds of 150 and 250 MeV for particles with | η | <
1. The correspondingrelative differences in the measured f CSE fractions are 1.1–5.8% and are assigned as systematicuncertainties.
Background subtraction method : The background determined using the SS method is comparedwith the adopted NBD background approach, and the difference is the associated system-atic uncertainty. This reflects the imperfect knowledge of the N tracks distributions for color-exchange dijet events. At lower p jet2T values, with 40 < p jet2T <
50 GeV, the relative systematicuncertainty is 14.6%, whereas for larger values, p jet2T >
80 GeV, it is 2–5%.
NBD fit parameters:
The NBD function has three free parameters, including an overall normal-ization. The color-exchange dijet yields in the signal region are recalculated by varying theNBD fit parameters within their uncertainties. Correlations between the fit parameters are in-cluded in this procedure. The maximal differences relative to the nominal results are a measureof the associated systematic uncertainty. These calculations result in a relative uncertainty ofless than 2.6% in the extracted f CSE . .2 Systematic uncertainties in the study of proton-gap-jet-gap-jet events A summary of the systematic uncertainties is presented in Table 1. The systematic uncertaintiesare added in quadrature and the total bin-specific systematic uncertainty varies between 6.8and 22%.As mentioned in Section 5, no neutral particles are used in the definition of the pseudorapid-ity gap because of the relatively large p T thresholds above the calorimeter noise for neutralhadrons and photons. Most dijet events with low N tracks in the region | η | < | η | < f CSE fractions remain mostlyunaffected if the contribution of neutral particles at central η is included in the analysis. In par-ticular, if the vector p T sum of the neutral hadrons and photons for | η | < f CSE are the same, within the statistical uncertainties of f CSE . This isconsistent since the color-exchange dijet background is already subtracted in the determinationof f CSE .Table 1: Relative systematic uncertainties in percentage for the measurements of f CSE in jet-gap-jet and proton-gap-jet-gap-jet events. The jet-gap-jet results summarize the systematic un-certainties in bins of the kinematic variables of interest p jet2T , ∆ η jj , and ∆ φ jj . When an uncertaintyrange is given, the range of values is representative of the variation found in f CSE in bins of thekinematic variables of interest.Source Jet-gap-jet (%) Proton-gap-jet-gap-jet (%) ∆ η jj p jet2T ∆ φ jj Jet energy scale 1.0–5.0 1.5–6.0 0.5–3.0 0.7Track quality 6.0–8.0 5.4–8.0 1.5–8.0 8Charged particle p T threshold 2.0–5.8 1.6–4.0 1.1–5.8 11Background subtraction method 4.7–15 2–15 12 28NBD fit parameters 0.8–2.6 0.6–1.7 0.1–0.6 7.0NBD fit interval — — — 12Calorimeter energy scale — — — 5.0Horizontal dispersion — — — 6.0Fiducial selection requirements — — — 2.6Total 6.8–22 8.3–15 12–17 33 In addition to the sources of systematic uncertainties described in Section 8.1, the followingsources of systematic uncertainties that affect the extraction of f CSE in proton-gap-jet-gap-jetevents are considered:
NBD fit interval:
Because of the lower mean N tracks and the limited sample size, the NBD fitextrapolation is more sensitive to the fit interval in events with an intact proton than in inclusivedijet production. The color-exchange dijet background for intervals of 2 ≤ N tracks ≤
15 and2 ≤ N tracks ≤
35 is evaluated. The difference of the extracted f CSE value for these intervalsrelative to that for the nominal interval 2 ≤ N tracks ≤
25 is taken as the associated systematicuncertainty. Based on these studies an uncertainty of 12% is assigned to the extracted f CSE .The difference of the measured f CSE value using the fit interval 3 ≤ N tracks ≤
25 relative to thenominal fit interval is negligible.
Calorimeter energy scale:
Beam background contributions are suppressed via the requirement ξ p ( PF ) − ξ p ( RP ) < ξ p ( PF ) is constructed from the PF candidates ofthe CMS experiment, it is affected by the energy calibration uncertainties of each PF candidate.The impact on ξ p ( PF ) is estimated by varying the energy of the PF candidates conservativelyby ±
10% [67]. The corresponding relative difference in the extracted f CSE value is 5%, and isincluded as the associated systematic uncertainty.
Horizontal dispersion:
The determination of ξ p ( RP ) depends on the LHC optics parametrizationin the transport matrix, which connects the kinematics of the proton at the interaction pointwith those measured at the RPs. The horizontal dispersion term in the transport matrix directlyaffects the measurement of ξ p ( RP ) [64]. The associated systematic uncertainty is estimated byconservatively scaling the value of ξ p ( RP ) by ± f CSE hasan uncertainty of 6%.
Fiducial selection requirements for x ( RP ) –y ( RP ) coordinates at the RPs: The vertical and horizontalfiducial requirements are varied by 0.2 and 1 mm, respectively. The relative difference of the f CSE result with respect to that obtained with the nominal fiducial x ( RP ) – y ( RP ) requirementsis less than 2.6%, and is assigned as the corresponding systematic uncertainty.The systematic uncertainties are summarized in Table 1. The systematic uncertainties related tothe jet reconstruction and central gap definition are larger in the proton-gap-jet-gap-jet study.The total systematic uncertainty is calculated as the quadratic sum of the individual contribu-tions, and is has a value of 33%. The measured fractions f CSE are presented in Fig. 8 and Tables 2–4. As a function of ∆ η jj , the f CSE fraction shows a uniform increase from 0.4 to 1.0% for ∆ η jj between 3 and 6 units. Withinthe experimental uncertainties, f CSE is about 0.7%, and shows little, if any, dependence on p jet2T . As a function of ∆ φ jj between the two leading jets, the f CSE fraction exhibits a peak near ∆ φ jj = π with a value of 1%, which suggests that jet-gap-jet events are more strongly correlatedin the transverse plane than inclusive dijet events. A constant value of about 0.4% is found for ∆ φ jj < |S | = f CSE values observed in data. The RMK predictions use an updatedparametrization of the BFKL NLL amplitudes that include the larger phase space available atLHC energies [101], which are then implemented in the
HERWIG
PYTHIA .1 Results for jet-gap-jet events in inclusive dijet production hD [ % ] C SE f CMS (13 TeV) -1 | < 4.7 jet1,2 h < 0, 1.4 < | jet2 h jet1 h > 40 GeV jet2T pDataRMK (BFKL NLL)EEIM (BFKL NLL+MPI)EEIM (BFKL NLL+MPI+SCI) 40 60 80 100 120 140 160 180 200 [GeV] jet2T p [ % ] C SE f CMS (13 TeV) -1 | < 4.7 jet1,2 h < 0, 1.4 < | jet2 h jet1 h > 40 GeV jet2T pDataRMK (BFKL NLL)EEIM (BFKL NLL+MPI)EEIM (BFKL NLL+MPI+SCI)0 0.5 1 1.5 2 2.5 3 [rad] jj fD [ % ] C SE f CMS (13 TeV) -1 | < 4.7 jet1,2 h < 0, 1.4 < | jet2 h jet1 h > 40 GeV jet2T p DataRMK (BFKL NLL) Figure 8: Fraction of color-singlet exchange dijet events, f CSE , measured as a function of ∆ η jj , p jet2T , and ∆ φ jj in pp collisions at √ s =
13 TeV. Vertical bars represent statistical uncertainties,while boxes represent the combination of statistical and systematic uncertainties in quadrature.The results are plotted at the mean values of ∆ η jj , p jet2T , and ∆ φ jj in the bin. For a given plot of f CSE versus a kinematic variable of interest ( p jet2T , ∆ η jj , or ∆ φ jj ), the other kinematic variablesare integrated over their allowed range. The red solid curve corresponds to theoretical predic-tions based on the RMK model [54, 55] with gap survival probability of |S | = |S | = ∆ φ jj , has only small contributions far from back-to-back jets since no hard NLO 2 → of the SCI model are fit to describe the previous 7 TeV measurement by CMS [56]. The remain-ing nonperturbative corrections are either modeled with a survival probability of |S | = f CSE value found in data (purple dashed line in Fig. 8) or with SCI (orange dottedline in Fig. 8). The theoretical uncertainties in the EEIM model predictions are dominated bythe cutoff p T scale used for MPI in the simulation.Table 2: Measured values of the fraction of color-singlet exchange events f CSE in bins of thepseudorapidity difference between the two leading jets ∆ η jj . The first column indicates the ∆ η jj intervals and the last column represents the measured fraction. The first and second uncer-tainties correspond to the statistical and systematic components, respectively. The results areintegrated over the allowed p jet2T and ∆ φ jj values. The mean values of ∆ η jj in the bin are givenin the middle column. ∆ η jj (cid:104) ∆ η jj (cid:105) f CSE [%]3.0–3.5 3.24 0.41 ± + − ± + − ± + − ± + − ± + − ± + − ± + − ± + − ± + − ± + − Table 3: Measured values of the fraction of color-singlet exchange events f CSE in bins of thesubleading jet transverse momentum p jet2T . The first column indicates the p jet2T bin intervals andthe last column represents the measured fraction. The first and second uncertainties correspondto the statistical and systematic components, respectively. The results are integrated over theallowed ∆ η jj and ∆ φ jj values. The mean values of p jet2T in the bin are given in the middle column. p jet2T [GeV] (cid:104) p jet2T (cid:105) [GeV] f CSE [%]40–50 44.3 0.64 ± + − ± + − ± + − ± + − ± + − ± + − According to both the RMK and EEIM model calculations, f CSE should have a weak depen-dence on p jet2T . Within the uncertainties, this feature is consistent with the observed f CSE values.The predictions by RMK and EEIM (with MPI only) yield a decreasing f CSE with increasing ∆ η jj . This is in disagreement with the data, which show a f CSE that generally grows with larger ∆ η jj . The EEIM model predictions, when supplemented with SCI, correctly describe f CSE asa function of ∆ η jj within the uncertainties. The predictions of the RMK model for f CSE as a .1 Results for jet-gap-jet events in inclusive dijet production Table 4: Measured values of the fraction of color-singlet exchange events f CSE in bins of theazimuthal angular difference between the two leading jets ∆ φ jj . The first column indicates the ∆ φ jj bin intervals and the last column represents the measured fraction. The first and seconduncertainties correspond to the statistical and systematic components, respectively. The resultsare integrated over the allowed p jet2T and ∆ η jj values. The mean values of ∆ φ jj in the bin aregiven in the middle column. ∆ φ jj (cid:104) ∆ φ jj (cid:105) f CSE [%]0.00–1.00 0.60 0.54 ± + − ± + − ± + − ± + − ± + − ± + − π ± + − function of ∆ φ jj are consistent with the data within the uncertainties for medium angular sep-arations 1 < ∆ φ jj <
3, but underestimate the experimental result by about 10% near ∆ φ jj = π .The model significantly underestimates the observed f CSE for small angular separations with ∆ φ jj <
1. The EEIM model uses LO 2 → ∆ φ jj ≈ π , with only small deviations due to the leading logarithmic parton showers,but no hard next-to-LO (NLO) 2 → α S within the BFKL framework,namely resummation of large logarithms of energy at NLL accuracy using LO impact factors.Higher-order corrections to impact factors are known to have significant effects in the descrip-tion of similar processes, such as Mueller–Navelet jets [102]. Recently, major progress has beenmade in the calculation of NLO impact factors for the jet-gap-jet process [78, 79]. These correc-tions have yet to be included in the BFKL theoretical calculations to complete the NLO analysisof the jet-gap-jet process.In Fig. 9, the current results are compared with previous measurements of f CSE with a centralgap in | η | < √ s = k T algorithms)has a negligible effect on the shape of the charged particle multiplicity distribution betweenthe jets. The value of the distance parameter R influences the charged particle multiplicity dis-tribution shape of jet-gap-jet signal events. For large values of R , it is less likely for chargedparticle constituents of the jet to populate the central | η | < N tracks = R , there is morespillage of charged particles into the gap region, since the jet axes can approach the edge of the | η | < R . In these simulation studies, these effects arenegligible provided that f CSE is extracted over the first multiplicity bins N tracks <
3, as is donein this measurement.
20 40 60 80 100 120 140 160 180 200 220 [GeV] jet2T p [ % ] C SE f CMS | < 1 h Gap in | < 0 jet2 h jet1 h = 0.63 TeVsCDF | < 3.5, cone (R = 0.7) jet1,2 h = 0.63 TeVsD0 | < 4.1, cone (R = 0.7) jet1,2 h = 1.8 TeVsCDF | < 3.5, cone (R = 0.7) jet1,2 h = 1.8 TeVsD0 | < 4.1, cone (R = 0.7) jet1,2 h = 7 TeVsCMS (R = 0.5) t | < 4.7, anti-k jet1,2 h -1 = 13 TeV, 0.66 pbsCMS (R = 0.4) t | < 4.7, anti-k jet1,2 h Figure 9: Fraction of color-singlet exchange dijet events, f CSE , measured as a function of p jet2T by the D0 and CDF Collaborations [43, 45, 46] at √ s = | η | < | η | <
1, where each calorimeter tower has transverse energy E T >
200 MeV. The 0.63 and1.8 TeV studies consider jets with E jetT >
12 GeV and 1.9 < | η jet | < N tracks value in the region | η | < E T >
300 MeV is used in the CDF analyses. Each of the two leading jets has 1.8 < | η jet | < E jetT > >
20 GeV for the 0.63 and 1.8 TeV studies, respectively.The jets are clustered using the cone algorithm with R = p jet2T = k T algorithm with R = < | η jet | < N tracks distribution with p T >
200 MeV in | η | < f CSE decreases by a factor of 2.5 ± ± √ s increases from 0.63 to 1.8 TeV. Similarly, the results bythe CMS experiment at 7 TeV show a f CSE that decreases by a factor of around 2 with respect tothe 1.8 TeV results at the Tevatron [47]. The observed energy dependence of the previous mea-surements is generally attributed to a larger number of soft parton interactions with increasing √ s , which enhances the probability of the gap being destroyed. The 13 TeV results show thereis no further decrease of the f CSE values relative to the 7 TeV results, within the uncertainties.This could be an indication that the rapidity gap survival probability stops decreasing at thecenter-of-mass energies probed at the LHC for the jet-gap-jet process. .2 Results for jet-gap-jet events with an intact proton jj hD [ % ] C SE f CMS | < 1 h Gap in | < 0 jet2 h jet1 h = 7 TeVsCMS < 60 GeV jet2T
40 < p (R = 0.5) t | < 4.7, anti-k jet1,2 h = 7 TeVsCMS < 100 GeV jet2T
60 < p (R = 0.5) t | < 4.7, anti-k jet1,2 h = 7 TeVsCMS < 200 GeV jet2T
100 < p (R = 0.5) t | < 4.7, anti-k jet1,2 h -1 = 13 TeV, 0.66 pbsCMS > 40 GeV jet2T p (R = 0.4) t | < 4.7, anti-k jet1,2 h Figure 10: Fraction of color-singlet exchange dijet events, f CSE , measured as a function of ∆ η jj by CMS at 7 TeV [47] and the present measurement at 13 TeV. The 7 TeV measurement wasperformed in three bins of p jet2T = f CSE expands the reach in ∆ η jj covered in the earlier 7 TeV CMSmeasurement [47], as seen in Fig. 10. The measurement of f CSE as a function of ∆ η jj at 7 TeV iscarried out in three bins of ∆ η jj = p jet2T . The dependenceof f CSE as a function of ∆ η jj at 13 TeV confirms the trend observed by CMS at 7 TeV and extendsthe range previously explored towards large values of 6.5 < ∆ η jj < The fraction f CSE in events with intact protons is f CSE = [ ± + − (syst) ] %. Al-though the dijet events with an intact proton cover the same phase space as those in the inclu-sive dijet analysis, most of the events used in the study populate the regions 3.0 < ∆ η jj < < p jet2T <
100 GeV because of the limited sample size of events with intact protons.The fraction f CSE in events with an intact proton is 2.91 ± + − (syst) times largerthan that extracted for inclusive dijet production, where the two leading jets have similar kine-matics to events with an intact proton, i.e., 40 < p jet2T <
100 GeV and 3.0 < ∆ η jj < f CSE ratio inthe latter jet-gap-jet subsample has a value of f CSE = [ ± + − (syst) ] %. Correla-tions of systematic uncertainties associated with jet reconstruction and central gap definitionare included when evaluating the uncertainties in the double ratios. Statistical and systematicuncertainties in the double ratio are largely dominated by the uncertainties in the CMS-TOTEM f CSE measurement. The CMS-TOTEM results, when compared with the CMS results extractedin inclusive dijet production, suggest that the relative abundance of dijet events with a central hD [ % ] C SE f CMS-TOTEM
13 TeV > 40 GeV jet2T | < 4.7, p jet1,2 h < 0, 1.4 < | jet2 h jet1 h -1 CMS, 0.66 pb(jet-gap-jet) -1 CMS-TOTEM, 0.40 pb(p-gap-jet-gap-jet) < 6.5 jj hD
40 60 80 100 120 140 160 [GeV] jet2T p [ % ] C SE f CMS-TOTEM
13 TeV | < 4.7 jet1,2 h < 0, 1.4 < | jet2 h jet1 h > 40 GeV jet2T p -1 CMS, 0.66 pb(jet-gap-jet) -1 CMS-TOTEM, 0.40 pb(p-gap-jet-gap-jet) < 100 GeV jet2T
40 < p
Figure 11: Fraction of hard color-singlet exchange dijet events f CSE , measured as a functionof ∆ η jj (left) and p jet2T (right) extracted in inclusive dijet event production (labeled CMS, repre-sented by the blue circle markers) and in dijet events with an intact proton at 13 TeV (labeledCMS-TOTEM, represented by the red cross marker). Vertical bars represent the statistical un-certainties, and boxes represent the combination of statistical and systematic uncertainties inquadrature. The CMS results are plotted at the mean values of ∆ η jj and p jet2T in the bin. TheCMS-TOTEM result is plotted at the mean value of ∆ η jj and p jet2T in the allowed range of thesevariables. The 40 < p jet2T <
100 GeV and 3.0 < ∆ η jj < gap is larger in events with an intact proton. This is illustrated in Fig. 11, where the results for f CSE are presented as a function of ∆ η jj and p jet2T .The larger f CSE value in events with an intact proton may reflect a reduced spectator partonactivity in reactions with an intact proton in comparison to the soft parton activity presentin interactions where the proton breaks up. In the latter, there can be soft parton exchangesbetween the proton remnants and partons produced in the collision, which can destroy thecentral gap signature between the final-state jets. A similar effect has been observed in otherdiffractive topologies in dijet events with two rapidity gaps by the CDF Collaboration at √ s = R SDND , and (ii) the ratio of double-pomeron exchange dijet events to single-diffractive dijet events, R DPESD . CDF finds that the dou-ble ratio has a value of R SDND / R DPESD = ± f CSE (jet-gap-jet)/ f CSE (p-gap-jet-gap-jet) = ± + − (syst),which is similar to that for the double-pomeron exchange dijet topology reported by CDF. Thepresent results further suggest that a gap is more likely to form or survive in the presence ofanother gap.
10 Summary
Events with two leading jets separated by a large pseudorapidity ( η ) gap have been studiedin proton-proton (pp) collisions at √ s =
13 TeV with the CMS and TOTEM experiments at theCERN LHC in 2015. The pseudorapidity gap is defined by the absence of charged particleswith transverse momentum p T >
200 MeV in the | η | < p T jets has 1.4 < | η jet | < p jetT >
40 GeV, with η jet1 η jet2 <
0, where jet1 and jet2 arethe leading and subleading jets in p T . The pseudorapidity gap signature is assumed to becaused by hard color-singlet exchange, which is described in terms of two-gluon exchange inperturbative quantum chromodynamics. Color-singlet exchange events appear as an excess ofevents over the expected charged particle multiplicity contribution from color-exchange dijetevents at the lowest charged particle multiplicity. The ratio of color-singlet exchange eventsto all dijet events, f CSE , has been measured as a function of p jet2T , the η difference between thetwo leading jets, ∆ η jj ≡ | η jet1 − η jet2 | , and the azimuthal angular separation between the twoleading jets, ∆ φ jj ≡ | φ jet1 − φ jet2 | .The measured f CSE values are in the range of 0.6–1.0%. The ratio f CSE increases with ∆ η jj , hasa weak dependence on p jet2T , and increases as ∆ φ jj approaches π . No significant difference in f CSE is observed between the 13 TeV results and those presented by the CMS Collaboration at7 TeV. This is in contrast to the trend found at lower energies of 0.63 and 1.8 TeV by the D0 andCDF Collaborations, where a significant decrease of f CSE with increasing √ s was observed, asillustrated in Fig. 9. The results are compared with calculations based on the Balitsky–Fadin–Kuraev–Lipatov framework [3–5] with resummation of large logarithms of energy at next-to-leading logarithmic accuracy using leading order impact factors, and various treatments of gapsurvival probability effects. The implementation by Royon, Marquet, and Kepka [54, 55] de-scribes some features of the data, but is not able to simultaneously describe all aspects of themeasurements. The implementation by Ekstedt, Enberg, Ingelman, and Motyka [53, 56] gives afair description of the data in ∆ η jj and p jet2T within the uncertainties only when considering sur-vival probability effects based on multiple-parton interactions and their soft color interactionmodel. In addition, a sample of dijet events with intact protons collected by the CMS and TOTEMexperiments is used to study jet-gap-jet events with intact protons, which correspond to proton-gap-jet-gap-jet topologies. This is the first analysis of this diffractive event topology. The f CSE value extracted in this sample is 2.91 ± + − (syst) times larger than that found ininclusive dijet production, possibly suggesting a larger abundance of jets with central gapsin events with detected intact protons. This can be interpreted in terms of a lower spectatorparton activity in events with intact protons, which decreases the likelihood of the central gapsignature being spoiled. Acknowledgments
We thank Andreas Ekstedt, Rikard Enberg, Gunnar Ingelman, Leszek Motyka and Cyrille Mar-quet, Oldrich Kepka for providing the BFKL predictions of their respective models.We congratulate our colleagues in the CERN accelerator departments for the excellent perfor-mance of the LHC and thank the technical and administrative staffs at CERN and at other CMSand TOTEM institutes for their contributions to the success of the CMS-TOTEM effort. In addi-tion, we gratefully acknowledge the computing centers and personnel of the Worldwide LHCComputing Grid and other centers for delivering so effectively the computing infrastructureessential to our analyses. Finally, we acknowledge the enduring support for the constructionand operation of the LHC, the CMS and TOTEM detectors, and the supporting computing in-frastructure provided by the following funding agencies: BMBWF and FWF (Austria); FNRSand FWO (Belgium); CNPq, CAPES, FAPERJ, FAPERGS, and FAPESP (Brazil); MES (Bulgaria);CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia);RIF (Cyprus); SENESCYT (Ecuador); MoER, ERC PUT and ERDF (Estonia); Academy of Fin-land, Finnish Academy of Science and Letters (The Vilho Yrj ¨o and Kalle V¨ais¨al¨a Fund), MEC,Magnus Ehrnrooth Foundation, HIP, and Waldemar von Frenckell Foundation (Finland); CEAand CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); the Circles ofKnowledge Club and NKFIA (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN(Italy); MSIP and NRF (Republic of Korea); MES (Latvia); LAS (Lithuania); MOE and UM(Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MOS (Mon-tenegro); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal);JINR (Dubna); MON, RosAtom, RAS, RFBR, and NRC KI (Russia); MESTD (Serbia); SEIDI,CPAN, PCTI, and FEDER (Spain); MOSTR (Sri Lanka); Swiss Funding Agencies (Switzerland);MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey);NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA).Individuals have received support from the Marie-Curie program and the European ResearchCouncil and Horizon 2020 Grant, contract Nos. 675440, 724704, 752730, and 765710 (EuropeanUnion); the Leventis Foundation; the Alfred P. Sloan Foundation; the Alexander von Hum-boldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation `a laRecherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Inno-vatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S.-FNRS and FWO (Belgium)under the “Excellence of Science – EOS” – be.h project n. 30820817; the Beijing Municipal Sci-ence & Technology Commission, No. Z191100007219010; the Ministry of Education, Youth andSports (MEYS) and MSMT CR of the Czech Republic; the Nylands nation vid Helsingfors uni-versitet (Finland); the Deutsche Forschungsgemeinschaft (DFG), under Germany’s ExcellenceStrategy – EXC 2121 “Quantum Universe” – 390833306, and under project number 400140256 -GRK2497; the Lend ¨ulet (“Momentum”) Program and the J´anos Bolyai Research Scholarship ofthe Hungarian Academy of Sciences, the New National Excellence Program ´UNKP, the NKFIA eferences research grants 123842, 123959, 124845, 124850, 125105, 128713, 128786, 129058, K 133046, andEFOP-3.6.1-16-2016-00001 (Hungary); the Council of Science and Industrial Research, India;the HOMING PLUS program of the Foundation for Polish Science, cofinanced from EuropeanUnion, Regional Development Fund, the Mobility Plus program of the Ministry of Scienceand Higher Education, including Grant No. MNiSW DIR/WK/2018/13, the National ScienceCenter (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2014/13/B/ST2/02543,2014/15/B/ST2/03998, and 2015/19/B/ST2/02861, Sonata-bis 2012/07/E/ST2/01406; theNational Priorities Research Program by Qatar National Research Fund; the Ministry of Scienceand Higher Education, project no. 0723-2020-0041 (Russia); the Tomsk Polytechnic UniversityCompetitiveness Enhancement Program; the Programa Estatal de Fomento de la Investigaci ´onCient´ıfica y T´ecnica de Excelencia Mar´ıa de Maeztu, grant MDM-2015-0509 and the ProgramaSevero Ochoa del Principado de Asturias; the Thalis and Aristeia programs cofinanced by EU-ESF and the Greek NSRF; the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chula-longkorn University and the Chulalongkorn Academic into Its 2nd Century Project Advance-ment Project (Thailand); the Kavli Foundation; the Nvidia Corporation; the SuperMicro Cor-poration; the Welch Foundation, contract C-1845; and the Weston Havens Foundation (USA). References [1] Particle Data Group, P. A. Zyla et al., “Review of particle physics”,
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Yerevan Physics Institute, Yerevan, Armenia
A.M. Sirunyan † , A. Tumasyan Institut f ¨ur Hochenergiephysik, Wien, Austria
W. Adam, F. Ambrogi, T. Bergauer, M. Dragicevic, J. Er ¨o, A. Escalante Del Valle, R. Fr ¨uhwirth ,M. Jeitler , N. Krammer, L. Lechner, D. Liko, T. Madlener, I. Mikulec, F.M. Pitters, N. Rad,J. Schieck , R. Sch ¨ofbeck, M. Spanring, S. Templ, W. Waltenberger, C.-E. Wulz , M. Zarucki Institute for Nuclear Problems, Minsk, Belarus
V. Chekhovsky, A. Litomin, V. Makarenko, J. Suarez Gonzalez
Universiteit Antwerpen, Antwerpen, Belgium
M.R. Darwish , E.A. De Wolf, D. Di Croce, X. Janssen, T. Kello , A. Lelek, M. Pieters,H. Rejeb Sfar, H. Van Haevermaet, P. Van Mechelen, S. Van Putte, N. Van Remortel Vrije Universiteit Brussel, Brussel, Belgium
F. Blekman, E.S. Bols, S.S. Chhibra, J. D’Hondt, J. De Clercq, D. Lontkovskyi, S. Lowette,I. Marchesini, S. Moortgat, A. Morton, Q. Python, S. Tavernier, W. Van Doninck, P. Van Mulders
Universit´e Libre de Bruxelles, Bruxelles, Belgium
D. Beghin, B. Bilin, B. Clerbaux, G. De Lentdecker, H. Delannoy, B. Dorney, L. Favart,A. Grebenyuk, A.K. Kalsi, I. Makarenko, L. Moureaux, L. P´etr´e, A. Popov, N. Postiau,E. Starling, L. Thomas, C. Vander Velde, P. Vanlaer, D. Vannerom, L. Wezenbeek
Ghent University, Ghent, Belgium
T. Cornelis, D. Dobur, M. Gruchala, I. Khvastunov , M. Niedziela, C. Roskas, K. Skovpen,M. Tytgat, W. Verbeke, B. Vermassen, M. Vit Universit´e Catholique de Louvain, Louvain-la-Neuve, Belgium
G. Bruno, F. Bury, C. Caputo, P. David, C. Delaere, M. Delcourt, I.S. Donertas, A. Giammanco,V. Lemaitre, K. Mondal, J. Prisciandaro, A. Taliercio, M. Teklishyn, P. Vischia, S. Wuyckens,J. Zobec
Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil
G.A. Alves, G. Correia Silva, C. Hensel, A. Moraes
Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
W.L. Ald´a J ´unior, E. Belchior Batista Das Chagas, H. BRANDAO MALBOUISSON,W. Carvalho, J. Chinellato , E. Coelho, E.M. Da Costa, G.G. Da Silveira , D. De Jesus Damiao,S. Fonseca De Souza, J. Martins , D. Matos Figueiredo, M. Medina Jaime , M. Melo De Almeida,C. Mora Herrera, L. Mundim, H. Nogima, P. Rebello Teles, L.J. Sanchez Rosas,A. Santoro, S.M. Silva Do Amaral, A. Sznajder, M. Thiel, E.J. Tonelli Manganote ,F. Torres Da Silva De Araujo, A. Vilela Pereira Universidade Estadual Paulista a , Universidade Federal do ABC b , S˜ao Paulo, Brazil C.A. Bernardes a , L. Calligaris a , T.R. Fernandez Perez Tomei a , E.M. Gregores b , D.S. Lemos a ,P.G. Mercadante b , S.F. Novaes a , Sandra S. Padula a Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia,Bulgaria
A. Aleksandrov, R. Hadjiiska, P. Iaydjiev, M. Misheva, M. Rodozov, M. Shopova, G. Sultanov
University of Sofia, Sofia, Bulgaria
M. Bonchev, A. Dimitrov, T. Ivanov, L. Litov, B. Pavlov, P. Petkov, A. Petrov Beihang University, Beijing, China
W. Fang , Q. Guo, H. Wang, L. Yuan Department of Physics, Tsinghua University, Beijing, China
M. Ahmad, Z. Hu, Y. Wang
Institute of High Energy Physics, Beijing, China
E. Chapon, G.M. Chen , H.S. Chen , M. Chen, D. Leggat, H. Liao, Z. Liu, R. Sharma, A. Spiezia,J. Tao, J. Thomas-wilsker, J. Wang, H. Zhang, S. Zhang , J. Zhao State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China
A. Agapitos, Y. Ban, C. Chen, A. Levin, J. Li, Q. Li, M. Lu, X. Lyu, Y. Mao, S.J. Qian, D. Wang,Q. Wang, J. Xiao
Sun Yat-Sen University, Guangzhou, China
Z. You
Institute of Modern Physics and Key Laboratory of Nuclear Physics and Ion-beamApplication (MOE) - Fudan University, Shanghai, China
X. Gao Zhejiang University, Hangzhou, China
M. Xiao
Universidad de Los Andes, Bogota, Colombia
C. Avila, A. Cabrera, C. Florez, J. Fraga, A. Sarkar, M.A. Segura Delgado
Universidad de Antioquia, Medellin, Colombia
J. Jaramillo, J. Mejia Guisao, F. Ramirez, J.D. Ruiz Alvarez, C.A. Salazar Gonz´alez,N. Vanegas Arbelaez
University of Split, Faculty of Electrical Engineering, Mechanical Engineering and NavalArchitecture, Split, Croatia
D. Giljanovic, N. Godinovic, D. Lelas, I. Puljak, T. Sculac
University of Split, Faculty of Science, Split, Croatia
Z. Antunovic, M. Kovac
Institute Rudjer Boskovic, Zagreb, Croatia
V. Brigljevic, D. Ferencek, D. Majumder, B. Mesic, M. Roguljic, A. Starodumov , T. Susa University of Cyprus, Nicosia, Cyprus
M.W. Ather, A. Attikis, E. Erodotou, A. Ioannou, G. Kole, M. Kolosova, S. Konstantinou,G. Mavromanolakis, J. Mousa, C. Nicolaou, F. Ptochos, P.A. Razis, H. Rykaczewski, H. Saka,D. Tsiakkouri
Charles University, Prague, Czech Republic
M. Finger , M. Finger Jr. , A. Kveton, J. Tomsa Escuela Politecnica Nacional, Quito, Ecuador
E. Ayala
Universidad San Francisco de Quito, Quito, Ecuador
E. Carrera Jarrin Academy of Scientific Research and Technology of the Arab Republic of Egypt, EgyptianNetwork of High Energy Physics, Cairo, Egypt
A.A. Abdelalim , S. Abu Zeid , S. Khalil Center for High Energy Physics (CHEP-FU), Fayoum University, El-Fayoum, Egypt
M.A. Mahmoud, Y. Mohammed National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
S. Bhowmik, A. Carvalho Antunes De Oliveira, R.K. Dewanjee, K. Ehataht, M. Kadastik,M. Raidal, C. Veelken
Department of Physics, University of Helsinki, Helsinki, Finland
P. Eerola, H. Kirschenmann, M. Voutilainen
Helsinki Institute of Physics, Helsinki, Finland
E. Br ¨ucken, J. Havukainen, V. Karim¨aki, M.S. Kim, R. Kinnunen, T. Lamp´en, K. Lassila-Perini,S. Laurila, S. Lehti, T. Lind´en, H. Siikonen, E. Tuominen, J. Tuominiemi
Lappeenranta University of Technology, Lappeenranta, Finland
P. Luukka, T. Tuuva
IRFU, CEA, Universit´e Paris-Saclay, Gif-sur-Yvette, France
M. Besancon, F. Couderc, M. Dejardin, D. Denegri, J.L. Faure, F. Ferri, S. Ganjour, A. Givernaud,P. Gras, G. Hamel de Monchenault, P. Jarry, B. Lenzi, E. Locci, J. Malcles, J. Rander,A. Rosowsky, M. ¨O. Sahin, A. Savoy-Navarro , M. Titov, G.B. Yu Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, Institut Polytechniquede Paris, Palaiseau, France
S. Ahuja, C. Amendola, F. Beaudette, M. Bonanomi, P. Busson, C. Charlot, O. Davignon, B. Diab,G. Falmagne, R. Granier de Cassagnac, A. Hakimi, I. Kucher, A. Lobanov, C. Martin Perez,M. Nguyen, C. Ochando, P. Paganini, J. Rembser, R. Salerno, J.B. Sauvan, Y. Sirois, A. Zabi,A. Zghiche
Universit´e de Strasbourg, CNRS, IPHC UMR 7178, Strasbourg, France
J.-L. Agram , J. Andrea, D. Bloch, G. Bourgatte, J.-M. Brom, E.C. Chabert, C. Collard, J.-C. Fontaine , D. Gel´e, U. Goerlach, C. Grimault, A.-C. Le Bihan, P. Van Hove Universit´e de Lyon, Universit´e Claude Bernard Lyon 1, CNRS-IN2P3, Institut de PhysiqueNucl´eaire de Lyon, Villeurbanne, France
E. Asilar, S. Beauceron, C. Bernet, G. Boudoul, C. Camen, A. Carle, N. Chanon,D. Contardo, P. Depasse, H. El Mamouni, J. Fay, S. Gascon, M. Gouzevitch, B. Ille, Sa. Jain,I.B. Laktineh, H. Lattaud, A. Lesauvage, M. Lethuillier, L. Mirabito, L. Torterotot, G. Touquet,M. Vander Donckt, S. Viret
Georgian Technical University, Tbilisi, Georgia
T. Toriashvili , Z. Tsamalaidze RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany
L. Feld, K. Klein, M. Lipinski, D. Meuser, A. Pauls, M. Preuten, M.P. Rauch, J. Schulz,M. Teroerde
RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany
D. Eliseev, M. Erdmann, P. Fackeldey, B. Fischer, S. Ghosh, T. Hebbeker, K. Hoepfner, H. Keller,L. Mastrolorenzo, M. Merschmeyer, A. Meyer, P. Millet, G. Mocellin, S. Mondal, S. Mukherjee, D. Noll, A. Novak, T. Pook, A. Pozdnyakov, T. Quast, M. Radziej, Y. Rath, H. Reithler, J. Roemer,A. Schmidt, S.C. Schuler, A. Sharma, S. Wiedenbeck, S. Zaleski
RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany
C. Dziwok, G. Fl ¨ugge, W. Haj Ahmad , O. Hlushchenko, T. Kress, A. Nowack, C. Pistone,O. Pooth, D. Roy, H. Sert, A. Stahl , T. Ziemons Deutsches Elektronen-Synchrotron, Hamburg, Germany
H. Aarup Petersen, M. Aldaya Martin, P. Asmuss, I. Babounikau, S. Baxter, O. Behnke,A. Berm ´udez Mart´ınez, A.A. Bin Anuar, K. Borras , V. Botta, D. Brunner, A. Campbell,A. Cardini, P. Connor, S. Consuegra Rodr´ıguez, V. Danilov, A. De Wit, M.M. Defranchis,L. Didukh, D. Dom´ınguez Damiani, G. Eckerlin, D. Eckstein, T. Eichhorn, A. Elwood,L.I. Estevez Banos, E. Gallo , A. Geiser, A. Giraldi, A. Grohsjean, M. Guthoff, A. Harb,A. Jafari , N.Z. Jomhari, H. Jung, A. Kasem , M. Kasemann, H. Kaveh, C. Kleinwort,J. Knolle, D. Kr ¨ucker, W. Lange, T. Lenz, J. Lidrych, K. Lipka, W. Lohmann , R. Mankel, I.-A. Melzer-Pellmann, J. Metwally, A.B. Meyer, M. Meyer, M. Missiroli, J. Mnich, A. Mussgiller,V. Myronenko, Y. Otarid, D. P´erez Ad´an, S.K. Pflitsch, D. Pitzl, A. Raspereza, A. Saggio,A. Saibel, M. Savitskyi, V. Scheurer, P. Sch ¨utze, C. Schwanenberger, R. Shevchenko, A. Singh,R.E. Sosa Ricardo, H. Tholen, N. Tonon, O. Turkot, A. Vagnerini, M. Van De Klundert, R. Walsh,D. Walter, Y. Wen, K. Wichmann, C. Wissing, S. Wuchterl, O. Zenaiev, R. Zlebcik University of Hamburg, Hamburg, Germany
R. Aggleton, S. Bein, L. Benato, A. Benecke, K. De Leo, T. Dreyer, A. Ebrahimi, F. Feindt,A. Fr ¨ohlich, C. Garbers, E. Garutti, P. Gunnellini, J. Haller, A. Hinzmann, A. Karavdina,G. Kasieczka, R. Klanner, R. Kogler, V. Kutzner, J. Lange, T. Lange, A. Malara, J. Multhaup,C.E.N. Niemeyer, A. Nigamova, K.J. Pena Rodriguez, O. Rieger, P. Schleper, S. Schumann,J. Schwandt, D. Schwarz, J. Sonneveld, H. Stadie, G. Steinbr ¨uck, B. Vormwald, I. Zoi
Karlsruher Institut fuer Technologie, Karlsruhe, Germany
M. Baselga, S. Baur, J. Bechtel, T. Berger, E. Butz, R. Caspart, T. Chwalek, W. De Boer,A. Dierlamm, A. Droll, K. El Morabit, N. Faltermann, K. Fl ¨oh, M. Giffels, A. Gottmann,F. Hartmann , C. Heidecker, U. Husemann, M.A. Iqbal, I. Katkov , P. Keicher, R. Koppenh ¨ofer,S. Maier, M. Metzler, S. Mitra, M.U. Mozer, D. M ¨uller, Th. M ¨uller, M. Musich, G. Quast,K. Rabbertz, J. Rauser, D. Savoiu, D. Sch¨afer, M. Schnepf, M. Schr ¨oder, D. Seith, I. Shvetsov,H.J. Simonis, R. Ulrich, M. Wassmer, M. Weber, C. W ¨ohrmann, R. Wolf, S. Wozniewski Institute of Nuclear and Particle Physics (INPP), NCSR Demokritos, Aghia Paraskevi,Greece
G. Anagnostou, P. Asenov, G. Daskalakis, T. Geralis, A. Kyriakis, D. Loukas, G. Paspalaki,A. Stakia
National and Kapodistrian University of Athens, Athens, Greece
M. Diamantopoulou, D. Karasavvas, G. Karathanasis, P. Kontaxakis, C.K. Koraka,A. Manousakis-katsikakis, A. Panagiotou, I. Papavergou, N. Saoulidou, K. Theofilatos,K. Vellidis, E. Vourliotis
National Technical University of Athens, Athens, Greece
G. Bakas, K. Kousouris, I. Papakrivopoulos, G. Tsipolitis, A. Zacharopoulou
University of Io´annina, Io´annina, Greece
I. Evangelou, C. Foudas, P. Gianneios, P. Katsoulis, P. Kokkas, S. Mallios, K. Manitara,N. Manthos, I. Papadopoulos, J. Strologas MTA-ELTE Lend ¨ulet CMS Particle and Nuclear Physics Group, E ¨otv ¨os Lor´and University,Budapest, Hungary
M. Bart ´ok , R. Chudasama, M.M.A. Gadallah , S. L ¨ok ¨os , P. Major, K. Mandal, A. Mehta,G. Pasztor, O. Sur´anyi, G.I. Veres Wigner Research Centre for Physics, Budapest, Hungary
G. Bencze, C. Hajdu, D. Horvath , F. Sikler, V. Veszpremi, G. Vesztergombi † Institute of Nuclear Research ATOMKI, Debrecen, Hungary
S. Czellar, J. Karancsi , J. Molnar, Z. Szillasi, D. Teyssier Institute of Physics, University of Debrecen, Debrecen, Hungary
P. Raics, Z.L. Trocsanyi, B. Ujvari
Indian Institute of Science (IISc), Bangalore, India
S. Choudhury, J.R. Komaragiri, D. Kumar, L. Panwar, P.C. Tiwari
National Institute of Science Education and Research, HBNI, Bhubaneswar, India
S. Bahinipati , D. Dash, C. Kar, P. Mal, T. Mishra, V.K. Muraleedharan Nair Bindhu,A. Nayak , D.K. Sahoo , N. Sur, S.K. Swain Panjab University, Chandigarh, India
S. Bansal, S.B. Beri, V. Bhatnagar, S. Chauhan, N. Dhingra , R. Gupta, A. Kaur, S. Kaur,P. Kumari, M. Lohan, M. Meena, K. Sandeep, S. Sharma, J.B. Singh, A.K. Virdi University of Delhi, Delhi, India
A. Ahmed, A. Bhardwaj, B.C. Choudhary, R.B. Garg, M. Gola, S. Keshri, A. Kumar,M. Naimuddin, P. Priyanka, K. Ranjan, A. Shah
Saha Institute of Nuclear Physics, HBNI, Kolkata, India
M. Bharti , R. Bhattacharya, S. Bhattacharya, D. Bhowmik, S. Dutta, S. Ghosh, B. Gomber ,M. Maity , S. Nandan, P. Palit, A. Purohit, P.K. Rout, G. Saha, S. Sarkar, M. Sharan, B. Singh ,S. Thakur Indian Institute of Technology Madras, Madras, India
P.K. Behera, S.C. Behera, P. Kalbhor, A. Muhammad, R. Pradhan, P.R. Pujahari, A. Sharma,A.K. Sikdar
Bhabha Atomic Research Centre, Mumbai, India
D. Dutta, V. Jha, V. Kumar, D.K. Mishra, K. Naskar , P.K. Netrakanti, L.M. Pant, P. Shukla Tata Institute of Fundamental Research-A, Mumbai, India
T. Aziz, M.A. Bhat, S. Dugad, R. Kumar Verma, U. Sarkar
Tata Institute of Fundamental Research-B, Mumbai, India
S. Banerjee, S. Bhattacharya, S. Chatterjee, P. Das, M. Guchait, S. Karmakar, S. Kumar,G. Majumder, K. Mazumdar, S. Mukherjee, D. Roy, N. Sahoo
Indian Institute of Science Education and Research (IISER), Pune, India
S. Dube, B. Kansal, A. Kapoor, K. Kothekar, S. Pandey, A. Rane, A. Rastogi, S. Sharma
Department of Physics, Isfahan University of Technology, Isfahan, Iran
H. Bakhshiansohi Institute for Research in Fundamental Sciences (IPM), Tehran, Iran
S. Chenarani , S.M. Etesami, M. Khakzad, M. Mohammadi Najafabadi University College Dublin, Dublin, Ireland
M. Felcini, M. Grunewald
INFN Sezione di Bari a , Universit`a di Bari b , Politecnico di Bari c , Bari, Italy M. Abbrescia a , b , R. Aly a , b ,39 , C. Aruta a , b , A. Colaleo a , D. Creanza a , c , N. De Filippis a , c ,M. De Palma a , b , A. Di Florio a , b , A. Di Pilato a , b , W. Elmetenawee a , b , L. Fiore a , A. Gelmi a , b ,M. Gul a , G. Iaselli a , c , M. Ince a , b , S. Lezki a , b , G. Maggi a , c , M. Maggi a , I. Margjeka a , b , J.A. Merlin a ,S. My a , b , S. Nuzzo a , b , A. Pompili a , b , G. Pugliese a , c , A. Ranieri a , G. Selvaggi a , b , L. Silvestris a ,F.M. Simone a , b , R. Venditti a , P. Verwilligen a INFN Sezione di Bologna a , Universit`a di Bologna b , Bologna, Italy G. Abbiendi a , C. Battilana a , b , D. Bonacorsi a , b , L. Borgonovi a , b , S. Braibant-Giacomelli a , b ,R. Campanini a , b , P. Capiluppi a , b , A. Castro a , b , F.R. Cavallo a , C. Ciocca a , M. Cuffiani a , b ,G.M. Dallavalle a , T. Diotalevi a , b , F. Fabbri a , A. Fanfani a , b , E. Fontanesi a , b , P. Giacomelli a ,L. Giommi a , b , C. Grandi a , L. Guiducci a , b , F. Iemmi a , b , S. Lo Meo a ,40 , S. Marcellini a , G. Masetti a ,F.L. Navarria a , b , A. Perrotta a , F. Primavera a , b , T. Rovelli a , b , G.P. Siroli a , b , N. Tosi a INFN Sezione di Catania a , Universit`a di Catania b , Catania, Italy S. Albergo a , b ,41 , S. Costa a , b , A. Di Mattia a , R. Potenza a , b , A. Tricomi a , b ,41 , C. Tuve a , b INFN Sezione di Firenze a , Universit`a di Firenze b , Firenze, Italy G. Barbagli a , A. Cassese a , R. Ceccarelli a , b , V. Ciulli a , b , C. Civinini a , R. D’Alessandro a , b , F. Fiori a ,E. Focardi a , b , G. Latino a , b , P. Lenzi a , b , M. Lizzo a , b , M. Meschini a , S. Paoletti a , R. Seidita a , b ,G. Sguazzoni a , L. Viliani a INFN Laboratori Nazionali di Frascati, Frascati, Italy
L. Benussi, S. Bianco, D. Piccolo
INFN Sezione di Genova a , Universit`a di Genova b , Genova, Italy F. Ferro a , R. Mulargia a , b , E. Robutti a , S. Tosi a , b INFN Sezione di Milano-Bicocca a , Universit`a di Milano-Bicocca b , Milano, Italy A. Benaglia a , A. Beschi a , b , F. Brivio a , b , F. Cetorelli a , b , V. Ciriolo a , b ,20 , F. De Guio a , b ,M.E. Dinardo a , b , P. Dini a , S. Gennai a , A. Ghezzi a , b , P. Govoni a , b , L. Guzzi a , b , M. Malberti a ,S. Malvezzi a , D. Menasce a , F. Monti a , b , L. Moroni a , M. Paganoni a , b , D. Pedrini a , S. Ragazzi a , b ,T. Tabarelli de Fatis a , b , D. Valsecchi a , b ,20 , D. Zuolo a , b INFN Sezione di Napoli a , Universit`a di Napoli ’Federico II’ b , Napoli, Italy, Universit`a dellaBasilicata c , Potenza, Italy, Universit`a G. Marconi d , Roma, Italy S. Buontempo a , N. Cavallo a , c , A. De Iorio a , b , F. Fabozzi a , c , F. Fienga a , A.O.M. Iorio a , b ,L. Layer a , b , L. Lista a , b , S. Meola a , d ,20 , P. Paolucci a ,20 , B. Rossi a , C. Sciacca a , b , E. Voevodina a , b INFN Sezione di Padova a , Universit`a di Padova b , Padova, Italy, Universit`a di Trento c ,Trento, Italy P. Azzi a , N. Bacchetta a , D. Bisello a , b , A. Boletti a , b , A. Bragagnolo a , b , R. Carlin a , b , P. Checchia a ,P. De Castro Manzano a , T. Dorigo a , F. Gasparini a , b , U. Gasparini a , b , S.Y. Hoh a , b , M. Margoni a , b ,A.T. Meneguzzo a , b , M. Presilla b , P. Ronchese a , b , R. Rossin a , b , F. Simonetto a , b , G. Strong,A. Tiko a , M. Tosi a , b , M. Zanetti a , b , P. Zotto a , b , A. Zucchetta a , b , G. Zumerle a , b INFN Sezione di Pavia a , Universit`a di Pavia b , Pavia, Italy A. Braghieri a , S. Calzaferri a , b , D. Fiorina a , b , P. Montagna a , b , S.P. Ratti a , b , V. Re a , M. Ressegotti a , b ,C. Riccardi a , b , P. Salvini a , I. Vai a , P. Vitulo a , b INFN Sezione di Perugia a , Universit`a di Perugia b , Perugia, Italy M. Biasini a , b , G.M. Bilei a , D. Ciangottini a , b , L. Fan `o a , b , P. Lariccia a , b , G. Mantovani a , b , V. Mariani a , b , M. Menichelli a , F. Moscatelli a , A. Rossi a , b , A. Santocchia a , b , D. Spiga a ,T. Tedeschi a , b INFN Sezione di Pisa a , Universit`a di Pisa b , Scuola Normale Superiore di Pisa c , Pisa Italy,Universit`a di Siena d , Siena, Italy K. Androsov a , P. Azzurri a , G. Bagliesi a , V. Bertacchi a , c , L. Bianchini a , T. Boccali a , R. Castaldi a ,M.A. Ciocci a , b , R. Dell’Orso a , M.R. Di Domenico a , d , S. Donato a , L. Giannini a , c , A. Giassi a ,M.T. Grippo a , F. Ligabue a , c , E. Manca a , c , G. Mandorli a , c , A. Messineo a , b , F. Palla a , G. Ramirez-Sanchez a , c , A. Rizzi a , b , G. Rolandi a , c , S. Roy Chowdhury a , c , N. Shafiei a , b , P. Spagnolo a ,R. Tenchini a , G. Tonelli a , b , A. Venturi a , P.G. Verdini a INFN Sezione di Roma a , Sapienza Universit`a di Roma b , Rome, Italy F. Cavallari a , M. Cipriani a , b , D. Del Re a , b , E. Di Marco a , M. Diemoz a , E. Longo a , b , P. Meridiani a ,G. Organtini a , b , F. Pandolfi a , R. Paramatti a , b , C. Quaranta a , b , S. Rahatlou a , b , C. Rovelli a ,F. Santanastasio a , b , L. Soffi a , b , R. Tramontano a , b INFN Sezione di Torino a , Universit`a di Torino b , Torino, Italy, Universit`a del PiemonteOrientale c , Novara, Italy N. Amapane a , b , R. Arcidiacono a , c , S. Argiro a , b , M. Arneodo a , c , N. Bartosik a , R. Bellan a , b ,A. Bellora a , b , C. Biino a , A. Cappati a , b , N. Cartiglia a , S. Cometti a , M. Costa a , b , R. Covarelli a , b ,N. Demaria a , B. Kiani a , b , F. Legger a , C. Mariotti a , S. Maselli a , E. Migliore a , b , V. Monaco a , b ,E. Monteil a , b , M. Monteno a , M.M. Obertino a , b , G. Ortona a , L. Pacher a , b , N. Pastrone a ,M. Pelliccioni a , G.L. Pinna Angioni a , b , M. Ruspa a , c , R. Salvatico a , b , F. Siviero a , b , V. Sola a ,A. Solano a , b , D. Soldi a , b , A. Staiano a , D. Trocino a , b INFN Sezione di Trieste a , Universit`a di Trieste b , Trieste, Italy S. Belforte a , V. Candelise a , b , M. Casarsa a , F. Cossutti a , A. Da Rold a , b , G. Della Ricca a , b ,F. Vazzoler a , b Kyungpook National University, Daegu, Korea
S. Dogra, C. Huh, B. Kim, D.H. Kim, G.N. Kim, J. Lee, S.W. Lee, C.S. Moon, Y.D. Oh, S.I. Pak,S. Sekmen, Y.C. Yang
Chonnam National University, Institute for Universe and Elementary Particles, Kwangju,Korea
H. Kim, D.H. Moon
Hanyang University, Seoul, Korea
B. Francois, T.J. Kim, J. Park
Korea University, Seoul, Korea
S. Cho, S. Choi, Y. Go, S. Ha, B. Hong, K. Lee, K.S. Lee, J. Lim, J. Park, S.K. Park, J. Yoo
Kyung Hee University, Department of Physics, Seoul, Republic of Korea
J. Goh, A. Gurtu
Sejong University, Seoul, Korea
H.S. Kim, Y. Kim
Seoul National University, Seoul, Korea
J. Almond, J.H. Bhyun, J. Choi, S. Jeon, J. Kim, J.S. Kim, S. Ko, H. Kwon, H. Lee, K. Lee, S. Lee,K. Nam, B.H. Oh, M. Oh, S.B. Oh, B.C. Radburn-Smith, H. Seo, U.K. Yang, I. Yoon
University of Seoul, Seoul, Korea
D. Jeon, J.H. Kim, B. Ko, J.S.H. Lee, I.C. Park, Y. Roh, D. Song, I.J. Watson Yonsei University, Department of Physics, Seoul, Korea
H.D. Yoo
Sungkyunkwan University, Suwon, Korea
Y. Choi, C. Hwang, Y. Jeong, H. Lee, Y. Lee, I. Yu
College of Engineering and Technology, American University of the Middle East (AUM),Egaila, Kuwait
Y. Maghrbi
Riga Technical University, Riga, Latvia
V. Veckalns Vilnius University, Vilnius, Lithuania
A. Juodagalvis, A. Rinkevicius, G. Tamulaitis
National Centre for Particle Physics, Universiti Malaya, Kuala Lumpur, Malaysia
W.A.T. Wan Abdullah, M.N. Yusli, Z. Zolkapli
Universidad de Sonora (UNISON), Hermosillo, Mexico
J.F. Benitez, A. Castaneda Hernandez, J.A. Murillo Quijada, L. Valencia Palomo
Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico
H. Castilla-Valdez, E. De La Cruz-Burelo, I. Heredia-De La Cruz , R. Lopez-Fernandez,A. Sanchez-Hernandez Universidad Iberoamericana, Mexico City, Mexico
S. Carrillo Moreno, C. Oropeza Barrera, M. Ramirez-Garcia, F. Vazquez Valencia
Benemerita Universidad Autonoma de Puebla, Puebla, Mexico
J. Eysermans, I. Pedraza, H.A. Salazar Ibarguen, C. Uribe Estrada
Universidad Aut ´onoma de San Luis Potos´ı, San Luis Potos´ı, Mexico
A. Morelos Pineda
University of Montenegro, Podgorica, Montenegro
J. Mijuskovic , N. Raicevic University of Auckland, Auckland, New Zealand
D. Krofcheck
University of Canterbury, Christchurch, New Zealand
S. Bheesette, P.H. Butler
National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan
A. Ahmad, M.I. Asghar, M.I.M. Awan, Q. Hassan, H.R. Hoorani, W.A. Khan, M.A. Shah,M. Shoaib, M. Waqas
National Centre for Nuclear Research, Swierk, Poland
H. Bialkowska, M. Bluj, B. Boimska, T. Frueboes, M. G ´orski, M. Kazana, M. Szleper, P. Traczyk,P. Zalewski
Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland
K. Bunkowski, A. Byszuk , K. Doroba, A. Kalinowski, M. Konecki, J. Krolikowski,M. Olszewski, M. Walczak Laborat ´orio de Instrumenta¸c˜ao e F´ısica Experimental de Part´ıculas, Lisboa, Portugal
M. Araujo, P. Bargassa, D. Bastos, P. Faccioli, M. Gallinaro, J. Hollar, N. Leonardo, T. Niknejad,J. Seixas, K. Shchelina, O. Toldaiev, J. Varela
Joint Institute for Nuclear Research, Dubna, Russia
S. Afanasiev, A. Baginyan, P. Bunin, A. Golunov, I. Golutvin, I. Gorbunov, A. Kamenev,V. Karjavine, I. Kashunin, V. Korenkov, A. Lanev, A. Malakhov, V. Matveev , P. Moisenz,V. Palichik, V. Perelygin, M. Savina, S. Shmatov, S. Shulha, V. Smirnov, O. Teryaev, N. Voytishin,A. Zarubin
Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia
G. Gavrilov, V. Golovtcov, Y. Ivanov, V. Kim , E. Kuznetsova , V. Murzin, V. Oreshkin,I. Smirnov, D. Sosnov, V. Sulimov, L. Uvarov, S. Volkov, A. Vorobyev Institute for Nuclear Research, Moscow, Russia
Yu. Andreev, A. Dermenev, S. Gninenko, N. Golubev, A. Karneyeu, M. Kirsanov, N. Krasnikov,A. Pashenkov, G. Pivovarov, D. Tlisov, A. Toropin
Institute for Theoretical and Experimental Physics named by A.I. Alikhanov of NRC‘Kurchatov Institute’, Moscow, Russia
V. Epshteyn, V. Gavrilov, N. Lychkovskaya, A. Nikitenko , V. Popov, I. Pozdnyakov,G. Safronov, A. Spiridonov, A. Stepennov, M. Toms, E. Vlasov, A. Zhokin Moscow Institute of Physics and Technology, Moscow, Russia
T. Aushev
National Research Nuclear University ’Moscow Engineering Physics Institute’ (MEPhI),Moscow, Russia
O. Bychkova, M. Chadeeva , D. Philippov, E. Popova, V. Rusinov P.N. Lebedev Physical Institute, Moscow, Russia
V. Andreev, M. Azarkin, I. Dremin, M. Kirakosyan, A. Terkulov
Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow,Russia
A. Belyaev, E. Boos, A. Ershov, A. Gribushin, L. Khein, V. Klyukhin, O. Kodolova, I. Lokhtin,O. Lukina, S. Obraztsov, S. Petrushanko, V. Savrin, A. Snigirev
Novosibirsk State University (NSU), Novosibirsk, Russia
V. Blinov , T. Dimova , L. Kardapoltsev , I. Ovtin , Y. Skovpen Institute for High Energy Physics of National Research Centre ‘Kurchatov Institute’,Protvino, Russia
I. Azhgirey, I. Bayshev, V. Kachanov, A. Kalinin, D. Konstantinov, V. Petrov, R. Ryutin, A. Sobol,S. Troshin, N. Tyurin, A. Uzunian, A. Volkov
National Research Tomsk Polytechnic University, Tomsk, Russia
A. Babaev, A. Iuzhakov, V. Okhotnikov, L. Sukhikh
University of Belgrade: Faculty of Physics and VINCA Institute of Nuclear Sciences,Belgrade, Serbia
P. Adzic , P. Cirkovic, M. Dordevic, P. Milenovic, J. Milosevic Centro de Investigaciones Energ´eticas Medioambientales y Tecnol ´ogicas (CIEMAT),Madrid, Spain
M. Aguilar-Benitez, J. Alcaraz Maestre, A. ´Alvarez Fern´andez, I. Bachiller, M. Barrio Luna, Cristina F. Bedoya, J.A. Brochero Cifuentes, C.A. Carrillo Montoya, M. Cepeda, M. Cerrada,N. Colino, B. De La Cruz, A. Delgado Peris, J.P. Fern´andez Ramos, J. Flix, M.C. Fouz,A. Garc´ıa Alonso, O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez, M.I. Josa, D. Moran,´A. Navarro Tobar, A. P´erez-Calero Yzquierdo, J. Puerta Pelayo, I. Redondo, L. Romero,S. S´anchez Navas, M.S. Soares, A. Triossi, C. Willmott
Universidad Aut ´onoma de Madrid, Madrid, Spain
C. Albajar, J.F. de Troc ´oniz, R. Reyes-Almanza
Universidad de Oviedo, Instituto Universitario de Ciencias y Tecnolog´ıas Espaciales deAsturias (ICTEA), Oviedo, Spain
B. Alvarez Gonzalez, J. Cuevas, C. Erice, J. Fernandez Menendez, S. Folgueras, I. Gonza-lez Caballero, E. Palencia Cortezon, C. Ram ´on ´Alvarez, V. Rodr´ıguez Bouza, S. Sanchez Cruz,A. Trapote
Instituto de F´ısica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain
I.J. Cabrillo, A. Calderon, B. Chazin Quero, J. Duarte Campderros, M. Fernandez,P.J. Fern´andez Manteca, G. Gomez, C. Martinez Rivero, P. Martinez Ruiz del Arbol, F. Matorras,J. Piedra Gomez, C. Prieels, F. Ricci-Tam, T. Rodrigo, A. Ruiz-Jimeno, L. Russo , L. Scodellaro,I. Vila, J.M. Vizan Garcia University of Colombo, Colombo, Sri Lanka
MK Jayananda, B. Kailasapathy , D.U.J. Sonnadara, DDC Wickramarathna University of Ruhuna, Department of Physics, Matara, Sri Lanka
W.G.D. Dharmaratna, K. Liyanage, N. Perera, N. Wickramage
CERN, European Organization for Nuclear Research, Geneva, Switzerland
T.K. Aarrestad, D. Abbaneo, B. Akgun, E. Auffray, G. Auzinger, P. Baillon, A.H. Ball,D. Barney, J. Bendavid, N. Beni, M. Bianco, A. Bocci, P. Bortignon, E. Brondolin, T. Camporesi,G. Cerminara, L. Cristella, D. d’Enterria, A. Dabrowski, N. Daci, V. Daponte, A. David,A. De Roeck, R. Di Maria, M. Dobson, M. D ¨unser, N. Dupont, A. Elliott-Peisert, N. Emriskova,F. Fallavollita , D. Fasanella, S. Fiorendi, G. Franzoni, J. Fulcher, W. Funk, D. Gigi, K. Gill,F. Glege, L. Gouskos, M. Guilbaud, D. Gulhan, M. Haranko, J. Hegeman, Y. Iiyama,V. Innocente, T. James, P. Janot, J. Kieseler, M. Komm, N. Kratochwil, C. Lange, P. Lecoq,K. Long, C. Lourenc¸o, L. Malgeri, M. Mannelli, A. Massironi, F. Meijers, S. Mersi, E. Meschi,F. Moortgat, M. Mulders, J. Ngadiuba, J. Niedziela, S. Orfanelli, L. Orsini, F. Pantaleo ,L. Pape, E. Perez, M. Peruzzi, A. Petrilli, G. Petrucciani, A. Pfeiffer, M. Pierini, D. Rabady,A. Racz, M. Rieger, M. Rovere, H. Sakulin, J. Salfeld-Nebgen, S. Scarfi, C. Sch¨afer, C. Schwick,M. Selvaggi, A. Sharma, P. Silva, P. Sphicas , J. Steggemann, S. Summers, V.R. Tavolaro,D. Treille, A. Tsirou, G.P. Van Onsem, A. Vartak, M. Verzetti, K.A. Wozniak, W.D. Zeuner Paul Scherrer Institut, Villigen, Switzerland
L. Caminada , W. Erdmann, R. Horisberger, Q. Ingram, H.C. Kaestli, D. Kotlinski,U. Langenegger, T. Rohe ETH Zurich - Institute for Particle Physics and Astrophysics (IPA), Zurich, Switzerland
M. Backhaus, P. Berger, A. Calandri, N. Chernyavskaya, G. Dissertori, M. Dittmar, M. Doneg`a,C. Dorfer, T. Gadek, T.A. G ´omez Espinosa, C. Grab, D. Hits, W. Lustermann, A.-M. Lyon, R.A. Manzoni, M.T. Meinhard, F. Micheli, F. Nessi-Tedaldi, F. Pauss, V. Perovic,G. Perrin, L. Perrozzi, S. Pigazzini, M.G. Ratti, M. Reichmann, C. Reissel, T. Reitenspiess,B. Ristic, D. Ruini, D.A. Sanz Becerra, M. Sch ¨onenberger, L. Shchutska, V. Stampf,M.L. Vesterbacka Olsson, R. Wallny, D.H. Zhu Universit¨at Z ¨urich, Zurich, Switzerland
C. Amsler , C. Botta, D. Brzhechko, M.F. Canelli, A. De Cosa, R. Del Burgo, J.K. Heikkil¨a,M. Huwiler, A. Jofrehei, B. Kilminster, S. Leontsinis, A. Macchiolo, P. Meiring, V.M. Mikuni,U. Molinatti, I. Neutelings, G. Rauco, A. Reimers, P. Robmann, K. Schweiger, Y. Takahashi,S. Wertz National Central University, Chung-Li, Taiwan
C. Adloff , C.M. Kuo, W. Lin, A. Roy, T. Sarkar , S.S. Yu National Taiwan University (NTU), Taipei, Taiwan
L. Ceard, P. Chang, Y. Chao, K.F. Chen, P.H. Chen, W.-S. Hou, Y.y. Li, R.-S. Lu, E. Paganis,A. Psallidas, A. Steen, E. Yazgan
Chulalongkorn University, Faculty of Science, Department of Physics, Bangkok, Thailand
B. Asavapibhop, C. Asawatangtrakuldee, N. Srimanobhas
C¸ ukurova University, Physics Department, Science and Art Faculty, Adana, Turkey
F. Boran, S. Damarseckin , Z.S. Demiroglu, F. Dolek, C. Dozen , I. Dumanoglu , E. Eskut,G. Gokbulut, Y. Guler, E. Gurpinar Guler , I. Hos , C. Isik, E.E. Kangal , O. Kara,A. Kayis Topaksu, U. Kiminsu, G. Onengut, K. Ozdemir , A. Polatoz, A.E. Simsek, B. Tali ,U.G. Tok, S. Turkcapar, I.S. Zorbakir, C. Zorbilmez Middle East Technical University, Physics Department, Ankara, Turkey
B. Isildak , G. Karapinar , K. Ocalan , M. Yalvac Bogazici University, Istanbul, Turkey
I.O. Atakisi, E. G ¨ulmez, M. Kaya , O. Kaya , ¨O. ¨Ozc¸elik, S. Tekten , E.A. Yetkin Istanbul Technical University, Istanbul, Turkey
A. Cakir, K. Cankocak , Y. Komurcu, S. Sen Istanbul University, Istanbul, Turkey
F. Aydogmus Sen, S. Cerci , S. Ozkorucuklu, D. Sunar Cerci Institute for Scintillation Materials of National Academy of Science of Ukraine, Kharkov,Ukraine
B. Grynyov
National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine
L. Levchuk
University of Bristol, Bristol, United Kingdom
E. Bhal, S. Bologna, J.J. Brooke, E. Clement, D. Cussans, H. Flacher, J. Goldstein, G.P. Heath,H.F. Heath, L. Kreczko, B. Krikler, S. Paramesvaran, T. Sakuma, S. Seif El Nasr-Storey, V.J. Smith,J. Taylor, A. Titterton
Rutherford Appleton Laboratory, Didcot, United Kingdom
K.W. Bell, A. Belyaev , C. Brew, R.M. Brown, D.J.A. Cockerill, K.V. Ellis, K. Harder,S. Harper, J. Linacre, K. Manolopoulos, D.M. Newbold, E. Olaiya, D. Petyt, T. Reis, T. Schuh,C.H. Shepherd-Themistocleous, A. Thea, I.R. Tomalin, T. Williams Imperial College, London, United Kingdom
R. Bainbridge, P. Bloch, S. Bonomally, J. Borg, S. Breeze, O. Buchmuller, A. Bundock, V. Cepaitis,G.S. Chahal , D. Colling, P. Dauncey, G. Davies, M. Della Negra, P. Everaerts, G. Fedi, G. Hall,G. Iles, J. Langford, L. Lyons, A.-M. Magnan, S. Malik, A. Martelli, V. Milosevic, J. Nash ,V. Palladino, M. Pesaresi, D.M. Raymond, A. Richards, A. Rose, E. Scott, C. Seez, A. Shtipliyski, M. Stoye, A. Tapper, K. Uchida, T. Virdee , N. Wardle, S.N. Webb, D. Winterbottom,A.G. Zecchinelli, S.C. Zenz Brunel University, Uxbridge, United Kingdom
J.E. Cole, P.R. Hobson, A. Khan, P. Kyberd, C.K. Mackay, I.D. Reid, L. Teodorescu, S. Zahid
Baylor University, Waco, USA
A. Brinkerhoff, K. Call, B. Caraway, J. Dittmann, K. Hatakeyama, A.R. Kanuganti, C. Madrid,B. McMaster, N. Pastika, S. Sawant, C. Smith
Catholic University of America, Washington, DC, USA
R. Bartek, A. Dominguez, R. Uniyal, A.M. Vargas Hernandez
The University of Alabama, Tuscaloosa, USA
A. Buccilli, O. Charaf, S.I. Cooper, S.V. Gleyzer, C. Henderson, P. Rumerio, C. West
Boston University, Boston, USA
A. Akpinar, A. Albert, D. Arcaro, C. Cosby, Z. Demiragli, D. Gastler, C. Richardson, J. Rohlf,K. Salyer, D. Sperka, D. Spitzbart, I. Suarez, S. Yuan, D. Zou
Brown University, Providence, USA
G. Benelli, B. Burkle, X. Coubez , D. Cutts, Y.t. Duh, M. Hadley, U. Heintz, J.M. Hogan ,K.H.M. Kwok, E. Laird, G. Landsberg, K.T. Lau, J. Lee, M. Narain, S. Sagir , R. Syarif, E. Usai,W.Y. Wong, D. Yu, W. Zhang University of California, Davis, Davis, USA
R. Band, C. Brainerd, R. Breedon, M. Calderon De La Barca Sanchez, M. Chertok, J. Conway,R. Conway, P.T. Cox, R. Erbacher, C. Flores, G. Funk, F. Jensen, W. Ko † , O. Kukral, R. Lander,M. Mulhearn, D. Pellett, J. Pilot, M. Shi, D. Taylor, K. Tos, M. Tripathi, Y. Yao, F. Zhang University of California, Los Angeles, USA
M. Bachtis, R. Cousins, A. Dasgupta, A. Florent, D. Hamilton, J. Hauser, M. Ignatenko, T. Lam,N. Mccoll, W.A. Nash, S. Regnard, D. Saltzberg, C. Schnaible, B. Stone, V. Valuev
University of California, Riverside, Riverside, USA
K. Burt, Y. Chen, R. Clare, J.W. Gary, S.M.A. Ghiasi Shirazi, G. Hanson, G. Karapostoli,O.R. Long, N. Manganelli, M. Olmedo Negrete, M.I. Paneva, W. Si, S. Wimpenny, Y. Zhang
University of California, San Diego, La Jolla, USA
J.G. Branson, P. Chang, S. Cittolin, S. Cooperstein, N. Deelen, M. Derdzinski, J. Duarte,R. Gerosa, D. Gilbert, B. Hashemi, D. Klein, V. Krutelyov, J. Letts, M. Masciovecchio, S. May,S. Padhi, M. Pieri, V. Sharma, M. Tadel, F. W ¨urthwein, A. Yagil
University of California, Santa Barbara - Department of Physics, Santa Barbara, USA
N. Amin, C. Campagnari, M. Citron, A. Dorsett, V. Dutta, J. Incandela, B. Marsh, H. Mei,A. Ovcharova, H. Qu, M. Quinnan, J. Richman, U. Sarica, D. Stuart, S. Wang
California Institute of Technology, Pasadena, USA
D. Anderson, A. Bornheim, O. Cerri, I. Dutta, J.M. Lawhorn, N. Lu, J. Mao, H.B. Newman,T.Q. Nguyen, J. Pata, M. Spiropulu, J.R. Vlimant, S. Xie, Z. Zhang, R.Y. Zhu
Carnegie Mellon University, Pittsburgh, USA
J. Alison, M.B. Andrews, T. Ferguson, T. Mudholkar, M. Paulini, M. Sun, I. Vorobiev University of Colorado Boulder, Boulder, USA
J.P. Cumalat, W.T. Ford, E. MacDonald, T. Mulholland, R. Patel, A. Perloff, K. Stenson,K.A. Ulmer, S.R. Wagner
Cornell University, Ithaca, USA
J. Alexander, Y. Cheng, J. Chu, D.J. Cranshaw, A. Datta, A. Frankenthal, K. Mcdermott,J. Monroy, J.R. Patterson, D. Quach, A. Ryd, W. Sun, S.M. Tan, Z. Tao, J. Thom, P. Wittich,M. Zientek
Fermi National Accelerator Laboratory, Batavia, USA
S. Abdullin, M. Albrow, M. Alyari, G. Apollinari, A. Apresyan, A. Apyan, S. Banerjee,L.A.T. Bauerdick, A. Beretvas, D. Berry, J. Berryhill, P.C. Bhat, K. Burkett, J.N. Butler, A. Canepa,G.B. Cerati, H.W.K. Cheung, F. Chlebana, M. Cremonesi, V.D. Elvira, J. Freeman, Z. Gecse,E. Gottschalk, L. Gray, D. Green, S. Gr ¨unendahl, O. Gutsche, R.M. Harris, S. Hasegawa,R. Heller, T.C. Herwig, J. Hirschauer, B. Jayatilaka, S. Jindariani, M. Johnson, U. Joshi,T. Klijnsma, B. Klima, M.J. Kortelainen, S. Lammel, D. Lincoln, R. Lipton, M. Liu, T. Liu,J. Lykken, K. Maeshima, D. Mason, P. McBride, P. Merkel, S. Mrenna, S. Nahn, V. O’Dell,V. Papadimitriou, K. Pedro, C. Pena , O. Prokofyev, F. Ravera, A. Reinsvold Hall, L. Ristori,B. Schneider, E. Sexton-Kennedy, N. Smith, A. Soha, W.J. Spalding, L. Spiegel, S. Stoynev,J. Strait, L. Taylor, S. Tkaczyk, N.V. Tran, L. Uplegger, E.W. Vaandering, M. Wang, H.A. Weber,A. Woodard University of Florida, Gainesville, USA
D. Acosta, P. Avery, D. Bourilkov, L. Cadamuro, V. Cherepanov, F. Errico, R.D. Field,D. Guerrero, B.M. Joshi, M. Kim, J. Konigsberg, A. Korytov, K.H. Lo, K. Matchev, N. Menendez,G. Mitselmakher, D. Rosenzweig, K. Shi, J. Wang, S. Wang, X. Zuo
Florida International University, Miami, USA
Y.R. Joshi
Florida State University, Tallahassee, USA
T. Adams, A. Askew, D. Diaz, R. Habibullah, S. Hagopian, V. Hagopian, K.F. Johnson,R. Khurana, T. Kolberg, G. Martinez, H. Prosper, C. Schiber, R. Yohay, J. Zhang
Florida Institute of Technology, Melbourne, USA
M.M. Baarmand, S. Butalla, T. Elkafrawy , M. Hohlmann, D. Noonan, M. Rahmani,M. Saunders, F. Yumiceva University of Illinois at Chicago (UIC), Chicago, USA
M.R. Adams, L. Apanasevich, H. Becerril Gonzalez, R. Cavanaugh, X. Chen, S. Dittmer,O. Evdokimov, C.E. Gerber, D.A. Hangal, D.J. Hofman, C. Mills, G. Oh, T. Roy, M.B. Tonjes,N. Varelas, J. Viinikainen, H. Wang, X. Wang, Z. Wu
The University of Iowa, Iowa City, USA
M. Alhusseini, B. Bilki , K. Dilsiz , S. Durgut, R.P. Gandrajula, M. Haytmyradov,V. Khristenko, O.K. K ¨oseyan, J.-P. Merlo, A. Mestvirishvili , A. Moeller, J. Nachtman,H. Ogul , Y. Onel, F. Ozok , A. Penzo, C. Snyder, E. Tiras, J. Wetzel, K. Yi Johns Hopkins University, Baltimore, USA
O. Amram, B. Blumenfeld, L. Corcodilos, M. Eminizer, A.V. Gritsan, S. Kyriacou,P. Maksimovic, C. Mantilla, J. Roskes, M. Swartz, T. ´A. V´ami
The University of Kansas, Lawrence, USA P. Baringer, A. Bean, A. Bylinkin, S. Khalil, J. King, G. Krintiras, A. Kropivnitskaya, M. Murray,C. Rogan, S. Sanders, E. Schmitz, J.D. Tapia Takaki, Q. Wang, G. Wilson
Kansas State University, Manhattan, USA
S. Duric, A. Ivanov, K. Kaadze, D. Kim, Y. Maravin, D.R. Mendis, T. Mitchell, A. Modak,A. Mohammadi
Lawrence Livermore National Laboratory, Livermore, USA
F. Rebassoo, D. Wright
University of Maryland, College Park, USA
E. Adams, A. Baden, O. Baron, A. Belloni, S.C. Eno, Y. Feng, N.J. Hadley, S. Jabeen, G.Y. Jeng,R.G. Kellogg, T. Koeth, A.C. Mignerey, S. Nabili, M. Seidel, A. Skuja, S.C. Tonwar, L. Wang,K. Wong
Massachusetts Institute of Technology, Cambridge, USA
D. Abercrombie, B. Allen, R. Bi, S. Brandt, W. Busza, I.A. Cali, Y. Chen, M. D’Alfonso,G. Gomez Ceballos, M. Goncharov, P. Harris, D. Hsu, M. Hu, M. Klute, D. Kovalskyi, J. Krupa,Y.-J. Lee, P.D. Luckey, B. Maier, A.C. Marini, C. Mcginn, C. Mironov, S. Narayanan, X. Niu,C. Paus, D. Rankin, C. Roland, G. Roland, Z. Shi, G.S.F. Stephans, K. Sumorok, K. Tatar,D. Velicanu, J. Wang, T.W. Wang, Z. Wang, B. Wyslouch
University of Minnesota, Minneapolis, USA
R.M. Chatterjee, A. Evans, S. Guts † , P. Hansen, J. Hiltbrand, Sh. Jain, M. Krohn, Y. Kubota,Z. Lesko, J. Mans, M. Revering, R. Rusack, R. Saradhy, N. Schroeder, N. Strobbe, M.A. Wadud University of Mississippi, Oxford, USA
J.G. Acosta, S. Oliveros
University of Nebraska-Lincoln, Lincoln, USA
K. Bloom, S. Chauhan, D.R. Claes, C. Fangmeier, L. Finco, F. Golf, J.R. Gonz´alez Fern´andez,I. Kravchenko, J.E. Siado, G.R. Snow † , B. Stieger, W. Tabb State University of New York at Buffalo, Buffalo, USA
G. Agarwal, C. Harrington, L. Hay, I. Iashvili, A. Kharchilava, C. McLean, D. Nguyen,A. Parker, J. Pekkanen, S. Rappoccio, B. Roozbahani
Northeastern University, Boston, USA
G. Alverson, E. Barberis, C. Freer, Y. Haddad, A. Hortiangtham, G. Madigan, B. Marzocchi,D.M. Morse, V. Nguyen, T. Orimoto, L. Skinnari, A. Tishelman-Charny, T. Wamorkar, B. Wang,A. Wisecarver, D. Wood
Northwestern University, Evanston, USA
S. Bhattacharya, J. Bueghly, Z. Chen, A. Gilbert, T. Gunter, K.A. Hahn, N. Odell, M.H. Schmitt,K. Sung, M. Velasco
University of Notre Dame, Notre Dame, USA
R. Bucci, N. Dev, R. Goldouzian, M. Hildreth, K. Hurtado Anampa, C. Jessop, D.J. Karmgard,K. Lannon, W. Li, N. Loukas, N. Marinelli, I. Mcalister, F. Meng, K. Mohrman, Y. Musienko ,R. Ruchti, P. Siddireddy, S. Taroni, M. Wayne, A. Wightman, M. Wolf, L. Zygala The Ohio State University, Columbus, USA
J. Alimena, B. Bylsma, B. Cardwell, L.S. Durkin, B. Francis, C. Hill, A. Lefeld, B.L. Winer,B.R. Yates Princeton University, Princeton, USA
G. Dezoort, P. Elmer, B. Greenberg, N. Haubrich, S. Higginbotham, A. Kalogeropoulos,G. Kopp, S. Kwan, D. Lange, M.T. Lucchini, J. Luo, D. Marlow, K. Mei, I. Ojalvo, J. Olsen,C. Palmer, P. Pirou´e, D. Stickland, C. Tully
University of Puerto Rico, Mayaguez, USA
S. Malik, S. Norberg
Purdue University, West Lafayette, USA
V.E. Barnes, R. Chawla, S. Das, L. Gutay, M. Jones, A.W. Jung, B. Mahakud, G. Negro,N. Neumeister, C.C. Peng, S. Piperov, H. Qiu, J.F. Schulte, N. Trevisani, F. Wang, R. Xiao, W. Xie
Purdue University Northwest, Hammond, USA
T. Cheng, J. Dolen, N. Parashar, M. Stojanovic
Rice University, Houston, USA
A. Baty, S. Dildick, K.M. Ecklund, S. Freed, F.J.M. Geurts, M. Kilpatrick, A. Kumar, W. Li,B.P. Padley, R. Redjimi, J. Roberts † , J. Rorie, W. Shi, A.G. Stahl Leiton, A. Zhang University of Rochester, Rochester, USA
A. Bodek, P. de Barbaro, R. Demina, J.L. Dulemba, C. Fallon, T. Ferbel, M. Galanti, A. Garcia-Bellido, O. Hindrichs, A. Khukhunaishvili, E. Ranken, R. Taus
The Rockefeller University, New York, USA
R. Ciesielski
Rutgers, The State University of New Jersey, Piscataway, USA
B. Chiarito, J.P. Chou, A. Gandrakota, Y. Gershtein, E. Halkiadakis, A. Hart, M. Heindl,E. Hughes, S. Kaplan, O. Karacheban , I. Laflotte, A. Lath, R. Montalvo, K. Nash, M. Osherson,S. Salur, S. Schnetzer, S. Somalwar, R. Stone, S.A. Thayil, S. Thomas University of Tennessee, Knoxville, USA
H. Acharya, A.G. Delannoy, S. Spanier
Texas A&M University, College Station, USA
O. Bouhali , M. Dalchenko, A. Delgado, R. Eusebi, J. Gilmore, T. Huang, T. Kamon , H. Kim,S. Luo, S. Malhotra, R. Mueller, D. Overton, L. Perni`e, D. Rathjens, A. Safonov, J. Sturdy Texas Tech University, Lubbock, USA
N. Akchurin, J. Damgov, V. Hegde, S. Kunori, K. Lamichhane, S.W. Lee, T. Mengke,S. Muthumuni, T. Peltola, S. Undleeb, I. Volobouev, Z. Wang, A. Whitbeck
Vanderbilt University, Nashville, USA
E. Appelt, S. Greene, A. Gurrola, R. Janjam, W. Johns, C. Maguire, A. Melo, H. Ni, K. Padeken,F. Romeo, P. Sheldon, S. Tuo, J. Velkovska, M. Verweij
University of Virginia, Charlottesville, USA
L. Ang, M.W. Arenton, B. Cox, G. Cummings, J. Hakala, R. Hirosky, M. Joyce, A. Ledovskoy,C. Neu, B. Tannenwald, Y. Wang, E. Wolfe, F. Xia
Wayne State University, Detroit, USA
P.E. Karchin, N. Poudyal, P. Thapa
University of Wisconsin - Madison, Madison, WI, USA
K. Black, T. Bose, J. Buchanan, C. Caillol, S. Dasu, I. De Bruyn, C. Galloni, H. He, M. Herndon,A. Herv´e, U. Hussain, A. Lanaro, A. Loeliger, R. Loveless, J. Madhusudanan Sreekala, A. Mallampalli, D. Pinna, T. Ruggles, A. Savin, V. Shang, V. Sharma, W.H. Smith, D. Teague,S. Trembath-reichert, W. Vetens†: Deceased1: Also at Vienna University of Technology, Vienna, Austria2: Also at Institute of Basic and Applied Sciences, Faculty of Engineering, Arab Academy forScience, Technology and Maritime Transport, Alexandria, Egypt, Alexandria, Egypt3: Also at Universit´e Libre de Bruxelles, Bruxelles, Belgium4: Also at IRFU, CEA, Universit´e Paris-Saclay, Gif-sur-Yvette, France5: Also at Universidade Estadual de Campinas, Campinas, Brazil6: Also at Federal University of Rio Grande do Sul, Porto Alegre, Brazil7: Also at Federal University of Mato Grosso do Sul (UFMS), Nova Andradina, Brazil8: Also at Universidade Federal de Pelotas, Pelotas, Brazil9: Also at University of Chinese Academy of Sciences, Beijing, China10: Also at Institute for Theoretical and Experimental Physics named by A.I. Alikhanov ofNRC ‘Kurchatov Institute’, Moscow, Russia11: Also at Joint Institute for Nuclear Research, Dubna, Russia12: Also at Helwan University, Cairo, Egypt13: Now at Zewail City of Science and Technology, Zewail, Egypt14: Also at Ain Shams University, Cairo, Egypt15: Now at Fayoum University, El-Fayoum, Egypt16: Also at Purdue University, West Lafayette, USA17: Also at Universit´e de Haute Alsace, Mulhouse, France18: Also at Tbilisi State University, Tbilisi, Georgia19: Also at Erzincan Binali Yildirim University, Erzincan, Turkey20: Also at CERN, European Organization for Nuclear Research, Geneva, Switzerland21: Also at RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany22: Also at University of Hamburg, Hamburg, Germany23: Also at Department of Physics, Isfahan University of Technology, Isfahan, Iran, Isfahan,Iran24: Also at Brandenburg University of Technology, Cottbus, Germany25: Also at Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University,Moscow, Russia26: Also at Institute of Physics, University of Debrecen, Debrecen, Hungary, Debrecen,Hungary27: Also at Physics Department, Faculty of Science, Assiut University, Assiut, Egypt28: Also at MTA-ELTE Lend ¨ulet CMS Particle and Nuclear Physics Group, E ¨otv ¨os Lor´andUniversity, Budapest, Hungary, Budapest, Hungary29: Also at Institute of Nuclear Research ATOMKI, Debrecen, Hungary30: Also at IIT Bhubaneswar, Bhubaneswar, India, Bhubaneswar, India31: Also at Institute of Physics, Bhubaneswar, India32: Also at G.H.G. Khalsa College, Punjab, India33: Also at Shoolini University, Solan, India34: Also at University of Hyderabad, Hyderabad, India35: Also at University of Visva-Bharati, Santiniketan, India36: Also at Indian Institute of Technology (IIT), Mumbai, India37: Also at Deutsches Elektronen-Synchrotron, Hamburg, Germany38: Also at Department of Physics, University of Science and Technology of Mazandaran,Behshahr, Iran39: Now at INFN Sezione di Bari a , Universit`a di Bari b , Politecnico di Bari c , Bari, Italy
40: Also at Italian National Agency for New Technologies, Energy and Sustainable EconomicDevelopment, Bologna, Italy41: Also at Centro Siciliano di Fisica Nucleare e di Struttura Della Materia, Catania, Italy42: Also at Riga Technical University, Riga, Latvia, Riga, Latvia43: Also at Consejo Nacional de Ciencia y Tecnolog´ıa, Mexico City, Mexico44: Also at Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland45: Also at Institute for Nuclear Research, Moscow, Russia46: Now at National Research Nuclear University ’Moscow Engineering Physics Institute’(MEPhI), Moscow, Russia47: Also at St. Petersburg State Polytechnical University, St. Petersburg, Russia48: Also at University of Florida, Gainesville, USA49: Also at Imperial College, London, United Kingdom50: Also at P.N. Lebedev Physical Institute, Moscow, Russia51: Also at Budker Institute of Nuclear Physics, Novosibirsk, Russia52: Also at Faculty of Physics, University of Belgrade, Belgrade, Serbia53: Also at Universit`a degli Studi di Siena, Siena, Italy, Siena, Italy54: Also at Trincomalee Campus, Eastern University, Sri Lanka, Nilaveli, Sri Lanka55: Also at INFN Sezione di Pavia a , Universit`a di Pavia b , Pavia, Italy, Pavia, Italy56: Also at National and Kapodistrian University of Athens, Athens, Greece57: Also at Universit¨at Z ¨urich, Zurich, Switzerland58: Also at Stefan Meyer Institute for Subatomic Physics, Vienna, Austria, Vienna, Austria59: Also at Laboratoire d’Annecy-le-Vieux de Physique des Particules, IN2P3-CNRS, Annecy-le-Vieux, France60: Also at S¸ ırnak University, Sirnak, Turkey61: Also at Department of Physics, Tsinghua University, Beijing, China, Beijing, China62: Also at Near East University, Research Center of Experimental Health Science, Nicosia,Turkey63: Also at Beykent University, Istanbul, Turkey, Istanbul, Turkey64: Also at Istanbul Aydin University, Application and Research Center for Advanced Studies(App. & Res. Cent. for Advanced Studies), Istanbul, Turkey65: Also at Mersin University, Mersin, Turkey66: Also at Piri Reis University, Istanbul, Turkey67: Also at Adiyaman University, Adiyaman, Turkey68: Also at Ozyegin University, Istanbul, Turkey69: Also at Izmir Institute of Technology, Izmir, Turkey70: Also at Necmettin Erbakan University, Konya, Turkey71: Also at Bozok Universitetesi Rekt ¨orl ¨ug ¨u, Yozgat, Turkey, Yozgat, Turkey72: Also at Marmara University, Istanbul, Turkey73: Also at Milli Savunma University, Istanbul, Turkey74: Also at Kafkas University, Kars, Turkey75: Also at Istanbul Bilgi University, Istanbul, Turkey76: Also at Hacettepe University, Ankara, Turkey77: Also at School of Physics and Astronomy, University of Southampton, Southampton,United Kingdom78: Also at IPPP Durham University, Durham, United Kingdom79: Also at Monash University, Faculty of Science, Clayton, Australia80: Also at Bethel University, St. Paul, Minneapolis, USA, St. Paul, USA81: Also at Karamano ˘glu Mehmetbey University, Karaman, Turkey82: Also at California Institute of Technology, Pasadena, USA
83: Also at Bingol University, Bingol, Turkey84: Also at Georgian Technical University, Tbilisi, Georgia85: Also at Sinop University, Sinop, Turkey86: Also at Mimar Sinan University, Istanbul, Istanbul, Turkey87: Also at Nanjing Normal University Department of Physics, Nanjing, China88: Also at Texas A&M University at Qatar, Doha, Qatar89: Also at Kyungpook National University, Daegu, Korea, Daegu, Korea
B The TOTEM Collaboration
G. Antchev a , P. Aspell , I. Atanassov a , V. Avati , J. Baechler , C. Baldenegro Barrera ,V. Berardi a ,4 b , M. Berretti a , V. Borchsh , E. Bossini b ,9 , U. Bottigli c , M. Bozzo a ,5 b ,H. Burkhardt , F.S. Cafagna a , M.G. Catanesi a , M. Csan´ad a , b , T. Cs ¨org˝o a ,3 b , M. Deile ,F. De Leonardis a ,4 c , M. Doubek c , D. Druzhkin , K. Eggert , V. Eremin d , A. Fiergolski ,L. Forthomme a ,2 b , F. Garcia a , V. Georgiev a , S. Giani , L. Grzanka , J. Hammerbauer a ,T. Isidori , V. Ivanchenko , M. Janda c , A. Karev , J. Kaˇspar b ,9 , B. Kaynak e , J. Kopal ,V. Kundr´at b , S. Lami a , R. Linhart a , C. Lindsey , M.V. Lokaj´ıˇcek †1 b , L. Losurdo c ,F. Lucas Rodr´ıguez , M. Macr´ı a , M. Malawski , N. Minafra , S. Minutoli a , T. Naaranoja a ,2 b ,F. Nemes a ,9 , H. Niewiadomski , T. Nov´ak b , E. Oliveri , F. Oljemark a ,2 b , M. Oriunno f ,K. ¨Osterberg a ,2 b , P. Palazzi , V. Passaro a ,4 c , Z. Peroutka a , J. Proch´azka b , M. Quinto a ,4 b ,E. Radermacher , E. Radicioni a , F. Ravotti , C. Royon , G. Ruggiero , H. Saarikko a ,2 b ,V.D. Samoylenko c , A. Scribano a , J. ˇSirok ´y a , J. Smajek , W. Snoeys , R. Stefanovitch ,J. Sziklai a , C. Taylor , E. Tcherniaev , N. Turini c , O. Urban a , V. Vacek c , O. Vavroch a ,J. Welti a ,2 b , J. Williams , J. Zich a , K. Zielinski ,†Deceased a University of West Bohemia, Pilsen, Czech Republic b Institute of Physics of the Academy of Sciences of the Czech Republic, Prague, CzechRepublic c Czech Technical University, Prague, Czech Republic a Helsinki Institute of Physics, University of Helsinki, Helsinki, Finland b Department of Physics, University of Helsinki, Helsinki, Finland a Wigner Research Centre for Physics, RMKI, Budapest, Hungary b Eszterhazy Karoly University KRC, Gy ¨ongy ¨os, Hungary a INFN Sezione di Bari, Bari, Italy b Dipartimento Interateneo di Fisica di Bari, University of Bari, Bari, Italy c Dipartimento di Ingegneria Elettrica e dell’Informazione — Politecnico di Bari, Bari, Italy a INFN Sezione di Genova, Genova, Italy b Universit`a degli Studi di Genova, Genova, Italy a INFN Sezione di Pisa, Pisa, Italy b Universit`a degli Studi di Pisa, Pisa, Italy c Universit`a degli Studi di Siena and Gruppo Collegato INFN di Siena, Siena, Italy Akademia G ´orniczo-Hutnicza (AGH) University of Science and Technology, Krakow, Poland Tomsk State University, Tomsk, Russia CERN, Geneva, Switzerland Case Western Reserve University, Department of Physics, Cleveland, OH, USA The University of Kansas, Lawrence, KS, USA a INRNE-BAS, Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia,Bulgaria b Department of Atomic Physics, E¨otv¨os Lor´and University, Budapest, Hungary c NRC ’Kurchatov Institute’–IHEP, Protvino, Russia d Ioffe Physical Technical Institute, Russian Academy of Sciences, St. Petersburg, Russian Federation e Istanbul University, Istanbul, Turkey ff