EEUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH
CERN-EP-2020-12216 June 2020c (cid:13)
Production of ω mesons in pp collisions at √ s = TeV
ALICE Collaboration ∗ Abstract
The invariant differential cross section of inclusive ω ( ) meson production at midrapidity ( | y | < .
5) in pp collisions at √ s = < p T <
17 GeV / c . The ω meson was reconstructed via its ω → π + π − π decay channel. The measured ω production cross section is compared to various calculations:PYTHIA 8.2 Monash 2013 describes the data, while PYTHIA 8.2 Tune 4C overestimates the databy about 50%. A recent NLO calculation, which includes a model describing the fragmentation ofthe whole vector-meson nonet, describes the data within uncertainties below 6 GeV / c , while it over-estimates the data by up to 50% for higher p T . The ω / π ratio is in agreement with previous mea-surements at lower collision energies and the PYTHIA calculations. In addition, the measurement iscompatible with transverse mass scaling within the measured p T range and the ratio is constant with C ω / π = . ± .
03 (stat) ± .
04 (sys) above a transverse momentum of 2 . / c . ∗ See Appendix A for the list of collaboration members a r X i v : . [ nu c l - e x ] J u l roduction of ω mesons in pp collisions at √ s = Measurements of hadron production cross sections in proton-proton (pp) collisions at high energies areimportant to test our understanding of strong interaction and its underlying theory of Quantum Chro-modynamics (QCD) [1]. Its perturbative treatment (pQCD) becomes feasible for predictions of particleproduction in hard scattering processes that have a sufficiently high momentum transfer Q . This is pos-sible by factorizing [2] the scattering process into three contributions: a QCD matrix element describingthe scattering of partons, a parton distribution function (PDF) [3] describing the probability to find ascattering parton within each colliding hadron, and a fragmentation function (FF) [4] that relates thefinal-state parton momentum to the momentum of an observed hadron. While the QCD matrix elementcan be calculated in pQCD for sufficiently hard scales, the FFs and PDFs are obtained by global fits ofexperimental data at various collision energies [5]. However, most particles are produced in soft scatter-ing processes that involve small momentum transfers and therefore can not be calculated within pQCD.In this regime, calculations rely on phenomenological models that also require experimental verification.Comparison of measured particle spectra with calculations is essential to test their underlying assump-tions and provide constraints for the FFs and the PDFs. For example, recent measurements of π and η mesons [6–8] at several LHC collision energies constrained gluon fragmentation [9] in a regime notaccessible by measurements at lower collision energies. Like the π and η mesons, the ω meson iscomprised mainly of light valence quarks and hence has similar flavor content. However, it has spin 1and is heavier than the π and η with a mass of 782 MeV / c [10]. These differences make the ω mesonan interesting complementary probe to improve our understanding of hadron production in high-energycollisions. Even though there have been several theoretical efforts to describe the fragmentation intopseudoscalar mesons and baryons such as π , K, η and protons [11, 12], only a few theoretical modelsexist to describe the fragmentation into vector mesons, due to a lack of experimental data. Nonetheless,recent efforts [13, 14] have been made to describe the fragmentation into the entire vector meson nonetusing a model with broken SU(3) symmetry by analysing RHIC (pp) and LEP ( e + e − ) data.This article presents the invariant differential cross section of inclusive ω meson production at mid-rapidity ( | y | < .
5) in pp collisions at √ s = ω production in hadronicinteractions has been measured at collision energies of √ s =
62 GeV [15] and √ s =
200 GeV [16–18]at ISR and RHIC respectively. At LHC energies, ω production has only been measured by ALICE atforward rapidities (2 . < y < .
0) in pp collision at 7 TeV [19] in a transverse momentum ( p T ) rangeof 1 < p T < / c . The results reported here provide the first measurement of ω production at mid-rapidity at LHC energies, and in a wide p T range of 2 < p T <
17 GeV / c , which tests existing calculationsin this regime and provides input for future theoretical studies of vector meson fragmentation functions.In addition, the ω / π production ratio as a function of p T is compared to results of measurements atlower collision energies. This ratio also tests the validity of transverse mass ( m T ) scaling [20] for ω mesons at LHC energies, which is typically applied to estimate hadronic backgrounds in direct photon ordi-electron measurements in situations where no measured hadron spectra are available. The empiricalscaling rule, which was established in measurements of identified particle spectra at lower collisionenergies at ISR and RHIC [21], states that the p T -differential yields of most particles can be described as E d σ (cid:14) d p = C h f ( m T ) , where f ( m T ) is a universal function for all hadron species and C h is a constantnormalisation factor.The article is structured as follows: Section 2 briefly describes the ALICE sub-detectors, with a focuson those relevant for the measurement. Details on the event selection and signal extraction are given inSecs. 3 to 5. Sources of systematic uncertainties are discussed in Sec. 6. The data and comparisons tomodel predictions are presented in Sec. 7. Finally, conclusions are provided in Sec. 8.2roduction of ω mesons in pp collisions at √ s = The ω meson was reconstructed via its decay to π + π − π , where in turn the π decays to two pho-tons. This strategy required the reconstruction of charged tracks in the ALICE central tracking system,composed of the Inner Tracking System (ITS) [22] and the Time Projection Chamber (TPC) [23], andthe reconstruction of photons using the ElectroMagnetic Calorimeter (EMCal) [24, 25] and the Pho-ton Spectrometer (PHOS) [26]. In addition, photons were reconstructed using the Photon ConversionMethod (PCM) [27], which exploits the capability of the central tracking system to reconstruct photonsfrom electron-positron track pairs. A detailed description of the ALICE detector system and its per-formance can be found in Refs. [28] and [27], respectively. Below, a brief overview of the previouslymentioned detectors and the V0 detector [29], used for the minimum bias trigger, is given.The ITS is positioned closest to the nominal interaction point and consists of two layers of SiliconPixel Detectors (SPD), two layers of Silicon Drift Detectors (SDD) and two outermost layers of SiliconStrip Detectors (SSD). The layers are positioned between 3 . . | η | < | η | < .
4, respectively.The SDD and SSD have a pseudorapidity coverage of | η | < . | η | < .
0, respectively. The ITS isused for the tracking of charged particles and the reconstruction of the primary vertex.The TPC is a large (90 m ) cylindrical drift detector, which allows for the measurement of chargedparticles and their identification via specific energy loss ( d E (cid:14) d x ) measurements. The TPC covers apseudorapidity range of | η | < . B = . p T ≈
100 MeV / c . For thereconstruction of charged particles in the ITS and TPC, a transverse momentum resolution of about 1%at 1 GeV / c is achieved, which decreases to about 3% at 10 GeV / c [23].The EMCal is a Pb-scintillator sampling calorimeter, which covered an azimuthal range of ∆ ϕ = ◦ and | η | < .
67 in pseudorapidity during 2010 data taking. In that period, it was comprised of 4 supermodules, each consisting of 288 modules. The module consists of four towers with a size of ≈ × ,corresponding to approximately twice the Molière radius. Each tower is made up of 140 alternating leadand scintillator layers, where the latter are connected to Avelanche Photo Diodes (APDs) that measure thescintillation light of the electromagnetic showers produced by particles traversing the lead absorber. Theenergy resolution is given by σ E / E = . / E ⊕ . / √ E ⊕ .
7% with energy E in units of GeV [25].The PHOS is an electromagnetic calorimeter with high granularity based on lead-tungstate (PbWO )scintillation crystals. At the time these data were collected, it had an acceptance of ∆ ϕ = ◦ and | η | < .
12, divided into three modules, each consisting of 3584 crystals that are connected to APDs. Ahigh granularity is achieved by small crystal size of ≈ . × . , where the lateral dimensions of thecells are only slightly larger than the PbWO Molière radius of 2 cm. The high light yield of the PbWO crystals operated at − ◦ C results in an energy resolution of σ E / E = . / E ⊕ . / √ E ⊕ .
1% withenergy E in units of GeV [30].The V0 detector provides the minimum bias triggers and is employed to reduce background events,such as beam-gas interactions and out-of-bunch pileup. It consists of two scintillator arrays locatedin the forward and backward rapidity regions of the ALICE apparatus, covering a pseudorapidity of2 . < η < . − . < η < − .
7, respectively.
The pp collision data used for the ω meson measurement were recorded by the ALICE experimentin 2010 at a centre-of-mass energy of √ s = OR , whichrequired a signal either in the SPD or in one of the V0 scintillator arrays, was used. The total inelastic3roduction of ω mesons in pp collisions at √ s = σ inel = . + . − . (model) ± . OR trigger was σ MB OR = ( . ± . ) mb. Beam-induced background events, such as beam-gas interactions or out-of-bunch pileup, are rejected offline by using the timing information from the V0 detectors and the numberof reconstructed hit points and track segments in the SPD, which are expected to be uncorrelated forbackground events. The rejection of in-bunch pileup events, where multiple interactions occur per bunchcrossing, was achieved by requiring that only a single primary vertex is reconstructed with the SPD perevent. Moreover, collision events with a reconstructed vertex more than 10 cm away from the nominalinteraction point along the beam axis were rejected. The integrated luminosities L int = N evt / σ MB OR were determined to be L EMCalint = . − and L PHOSint = . − for the measurement involving theEMCal and PHOS, respectively. The integrated luminosity of the sample using only the PCM for photonreconstruction amounts to L PCMint = . − .Charged pion trajectories (tracks) with | η | < . χ of the track refit procedure per TPC space point was required to be below 4 and tracks with amomentum below 100 MeV / c were rejected. The tracks were loosely constrained to the collision vertexby requiring a maximum distance of closest approach of a few centimeters to the collision vertex in beamdirection and transverse plane. The resolution of the transverse distance to the primary vertex for ITSand TPC charged particle tracks is below 150 µm for p T (cid:38) . / c [27]. Furthermore, charged pionscan be identified using the specific energy loss d E (cid:14) d x along the track in the TPC [32]. To enhance the probability of the reconstruction of π mesons, all methods to measure photons and π sat midrapidity with ALICE were exploited. The EMCal and the PHOS allow for the measurement ofphotons via their electromagnetic shower deposits above ∼ . p T by exploiting the e + e − pair creation by a photon within the innerdetector material. Looser photon selection criteria as in previous publications, see e.g. Ref. [33], wereapplied to increase the ω reconstruction efficiency.The electromagnetic shower produced in the EMCal or PHOS by an incoming particle usually spreadsover multiple adjacent towers, requiring the combination of the individual energy depositions to so-calledclusters, which is achieved by clusterisation algorithms [27]. Each reconstructed cluster in the EMCaland PHOS was required to have a total energy of E clus > . . ≈
150 ns intervals, a cut on the timing ofthe leading tower for EMCal clusters of −
100 ns < t cluster <
100 ns with respect to the collision timewas applied. Photon clusters were selected according to their cluster shape and, additionally, a track-matching procedure was applied to suppress clusters originating from charged particles reconstructedin the tracking system. The EMCal cluster shape is parametrised by the larger eigenvalue σ of thedispersion matrix of the shower shape ellipse [33, 34]. A requirement of 0 . ≤ σ ≤ . p T electron and hadron tracks that hit the calorimetersurface not perpendicularly and merged clusters. The latter mostly originate from high- p T neutral pionsthat decay with a small opening angle, resulting in both decay photons to be reconstructed as a singlecluster.Photons traversing the detector material of ALICE convert to an electron-positron pair with a probability4roduction of ω mesons in pp collisions at √ s = ) c (GeV/ p - p + p M C oun t s ALICE = 7 TeV s pp, triggered OR MB rec w/ PCM p c < 5.0 GeV/ T p < c : 4.0 GeV/ w Raw dataFitted BG using2nd order polynomialBG subtractedSignal fit 0.65 0.7 0.75 0.8 0.85 ) c (GeV/ p - p + p M · C oun t s ALICE = 7 TeV s pp, triggered OR MB rec w/ EMC p c < 8.0 GeV/ T p < c : 6.0 GeV/ w Raw dataFitted BG using2nd order polynomialBG subtractedSignal fit ) c (GeV/ p - p + p M C oun t s · ALICE = 7 TeV s pp, triggered OR MB rec w/ PHOS p c < 8.0 GeV/ T p < c : 6.0 GeV/ w Raw dataFitted BG using2nd order polynomialBG subtractedSignal fit
Fig. 1:
Invariant mass of π + π − π candidates shown in the vicinity of the nominal mass of the ω meson forindicated p T -ranges for π reconstruction with PCM (left), EMC (middle) and PHOS (right). The second orderpolynomial used for the background description is shown with a band denoting the statistical uncertainties of thefit. The points show the signal obtained after subtraction of the background fit. The signal is fitted with a Gaussian,where the vertical lines indicate the integration range used to obtain the raw yield by bin-by-bin counting, asoutlined in Sec. 5. of about 8.5% [27] within a radial distance of 180 cm from the beam axis. Such photons can be recon-structed using the PCM, which allows for the measurement of photons converting in the ITS and TPCwithin the fiducial acceptance of | η | < .
9. First, secondary vertices (V s) were reconstructed by analgorithm [35] exploiting the distinct topology of two tracks with opposite curvature that originate froma common point within the tracking detectors. Good reconstruction quality of the tracks associated witha secondary vertex was assured by requiring p T >
50 MeV / c and for the track to be comprised of at least60% of the findable TPC clusters. Tracks originating from electrons were identified via their specificenergy loss d E (cid:14) d x in the TPC, which was required to be within − σ e of the expected energy lossof electrons, where σ e is the standard deviation of the measured d E (cid:14) d x distribution of electrons. Con-tamination of charged pion tracks was suppressed by rejecting tracks whose d E (cid:14) d x was within ± σ π ± of the expected energy loss for pions. Several additional selection criteria were applied to identify V candidates originating from photon conversions, exploiting the kinematics and topology of the conver-sion, as discussed in more detail in Ref. [8]. These include, e.g. selections to assure that the momentumvector of a conversion pair is pointing towards the primary vertex and a selection based on the minimaldistance between the conversion point and the primary vertex, in order to remove contributions fromDalitz decays. Furthermore, the quality of the obtained V candidates was improved by constrainingthe reduced χ of the Kalman-filter hypothesis for the track pair. Remaining contamination from K , Λ and ¯ Λ decays was reduced by a selection based on the decay kinematics in an Armenteros-Podolanskiplot [36], where photon conversions contribute as symmetric decays of a particle with vanishing restmass. Compared to previous PCM measurements [8, 33], a p T dependence of the selection criteria wasintroduced to further reduce the contamination from K and Λ decays. In order to reconstruct the ω mesons via their π + π − π decay channel, where the π decays to two pho-tons with a branching ratio of ≈ π candidates from pairs of photon candidateswas applied. For the photons that passed the selection criteria, the two-photon invariant mass ( M γγ ) of allpossible photon pairs in a given event was calculated. Four different methods were used for the π can-didate reconstruction, differing in how the photons entering the M γγ calculation were selected. These arereferred to as PCM, PHOS and EMC, when both photons used for the π reconstruction were measuredwith the respective method. In addition, a hybrid method (PCM-EMC) was used, where one PCM pho-ton was combined with a photon measured with the EMCal. The resulting invariant mass distributions5roduction of ω mesons in pp collisions at √ s = ) c (GeV/ T p - - - r ec e (cid:215) A (cid:215) y D(cid:215)p = e PCMEMCPCM-EMCPHOS
ALICE simulation = 7 TeV s pp, p - p + p fi w Fig. 2:
Correction factors applied to the raw ω yields for each indicated π reconstruction method. The factorsinclude the geometrical acceptance A and the reconstruction efficiency ε rec. . In addition, a normalisation to unitrapidity and 2 π azimuth angle is applied to allow for a direct comparison between the different methods. exhibit a peak of photon pairs originating from π decays on top of combinatorial background. The peakwas parametrised in p T slices with a Gaussian to characterize the mean and width ( σ π ) of the π massdistribution. Photon pairs lying within about ± σ π of the expected π mass were selected as neutralpion candidates for the ω meson reconstruction. For the PHOS measurement [37], π candidates werefurthermore required to have both photons in the same PHOS module and to have a minimum transversemomentum of 1 . / c . Finally, the nominal neutral pion mass was assigned to the mass of selected π candidates in order to improve the ω mass resolution. This was achieved by subtracting the differencebetween the reconstructed π mass and its nominal mass from the reconstructed ω mass.Analogously to the π reconstruction, the invariant mass of all π + π − π combinations in a given eventwas determined by summing the four-momentum vectors of the candidate decay products passing theselection criteria. While charged pions were identified by requiring a d E (cid:14) d x within ± σ of their ex-pected energy loss, no such selection was applied for the ω analysis with the π reconstructed in PHOSto improve the ω reconstruction efficiency.Figure 1 shows the invariant mass distribution in the vicinity of the ω nominal mass for indicated p T in-tervals for the π reconstructed with PCM, EMC and PHOS, where a peak originating from ω mesondecays is clearly visible above the combinatorial background. The latter can be described using a sec-ond order polynomial for p T <
10 GeV / c . At higher momenta, a first order polynomial was used forthe PHOS measurement. The signal obtained after background subtraction was fitted with a Gaussianand the raw yield was obtained by adding counts within ± σ ω ( ± σ ω for PHOS) of the reconstructed ω mass, where σ ω denotes the standard deviation of the Gaussian ω signal fit. The ω mass resolutionwas found to be about 15 MeV / c with a slight dependence on p T and reconstruction technique. Thisis achieved by the use of the previously mentioned nominal mass assignment for π candidates, whichimproved the mass resolution by up to 30%.The obtained raw yields for each reconstruction method were corrected for geometrical acceptance andreconstruction efficiency, which were evaluated using Monte Carlo simulations. The event generatorPYTHIA6.2 [38] was used to simulate the minimum bias pp collisions, where the implemented kine-matics of the ω three-body decay are weighted assuming the experimentally observed phase space den-sity distributions [39, 40]. All final state particles were propagated through the ALICE detector usingGEANT 3 [41], taking into account the operating conditions of the detector at the time of data taking.6roduction of ω mesons in pp collisions at √ s = p T -dependent reconstructed π massand width in data. This agreement propagates to the ω candidates, where mass and width in data andMonte Carlo are found to be consistent within the statistical uncertainties. The full correction factors, ε , that were applied to the raw yields for the four different methods are shown in Fig. 2. These factorsinclude the geometrical acceptance evaluated for each method and the reconstruction efficiency, wherethe former is normalised to unit rapidity and 2 π azimuth angle to allow for a direct comparison betweenthe different methods. The use of the four reconstruction techniques combines the strengths of the in-dividual methods and maximizes the accessible p T reach. The reconstruction with PCM offers a low p T -reach, however, the efficiency is limited due to the low conversion probability of about 8.5%, whilethe reconstruction with the two calorimeters complements the measurement at high p T . The systematic and statistical uncertainties on the measured ω yield for the four individual reconstructiontechniques in exemplary p T intervals are summarised in Tab. 1. The uncertainties are given as relativeuncertainties of the measured values in percent. Table 1:
Overview of the relative uncertainties given in percent in exemplary p T -intervals for the four individualreconstruction techniques of the ω meson. The given categories summarise systematic uncertainties arising fromeach analysis step. For each method the statistical and total uncertainties are reported in addition, as well as theuncertainties of the combined measurement. The uncertainty from the σ MB OR determination of 3.5% is independentfrom the individual measurements and indicated separately in Fig. 3. p T interval 4 − c − c −
14 GeV/ c Method PCM PCM- EMC PCM PCM- EMC PHOS EMC PHOSEMC EMCSignal extraction 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The signal extraction dominates the systematic uncertainties of the measurement and includes uncer-tainties due to the yield extraction. For the PCM, PCM-EMC and EMC techniques the yield extractionuncertainty was estimated by varying simultaneously the bin-counting window used to obtain the rawyield in data and Monte Carlo and the fit range used for the polynomial fit of the combinatorial back-ground. Additionally, for the PHOS analysis, the signal region was excluded from the background fitand the signal was obtained by Gaussian integral instead of bin-by-bin counting. The material budgetuncertainty accounts for a possible mismatch between the amount of material present in the ALICE de-tector and its implementation in GEANT 3. The material budget uncertainty for a conversion photonwas studied in Ref. [6], and found to be 4.5% per photon. For the measurements involving the EMCalor the PHOS uncertainties of 3 and 3 . ω mesons in pp collisions at √ s = χ selection of the electron tracks and the requirementon the number of space points in the TPC for each track. For EMCal related measurements, the clusterenergy selection and the cluster shape have most influence on the uncertainty. For PHOS, the pho-ton reconstruction uncertainty was evaluated by variation of the track matching condition and clustershape selection. Uncertainties arising from the non-linearity and cluster energy scale of the respectivecalorimeters was taken into account by varying the scheme used to obtain the energy scale calibrationand are included in the overall calorimeter photon reconstruction uncertainty. Like the photon recon-struction uncertainties, the systematic uncertainties arising from the charged pion reconstruction wereestimated by independent variation of the selection criteria given in Sec. 3. To study the influence of in-bunch pileup on the measurement, the rejection criterium was loosened, resulting in a 0.5% systematicuncertainty. The systematic uncertainty due to the selection of neutral pion candidates was estimated byvarying the invariant mass selection window. For the PHOS measurement, the selection was additionallyvaried according to the π candidates transverse momentum. A detailed description of these sources ofuncertainty is provided in Refs. [33] and [37].Table 1 also shows, for each method, the statistical uncertainty together with the total systematic un-certainty, which is obtained by adding the individual sources in quadrature. In addition, the statisticaland systematic uncertainties of the combined measurement are given, which were obtained taken intoaccount correlations across the measurements as elaborated in the following section. The fully corrected invariant cross sections of ω production were obtained for each reconstruction tech-nique using E d σ pp → ω + X d p = π p T · L int · A · ε rec. · ω → π + π − π · N ω ∆ y ∆ p T . (1)Here, L Int is the integrated luminosity given in Sec. 3, ε rec. and A are the reconstruction efficiencyand acceptance of the corresponding method and BR = ( . ± . ) % is the branching ratio of the ω → π + π − π decay [10]. Moreover, N ω denotes the number of reconstructed ω mesons in the transversemomentum range ∆ p T and the given rapidity range ∆ y .The production cross sections were measured individually for each reconstruction method and thencombined using p T -dependent weights that are calculated according to the Best Linear Unbiased Es-timate (BLUE) algorithm [42], which uses concepts that are routinely applied in statistical fields. Thecombination took into account statistical and systematic uncertainties. For the systematic uncertainties,the individual measurements are found to be correlated by about 30%, dominantly originating from thecharged-pion selection and the material budget uncertainties. These correlations were taken into accountin the combination procedure. The statistical and systematic uncertainties of the combined measurementare given in Tab. 1.The cross section of ω meson production for 2 < p T <
17 GeV / c at midrapidity in pp collisions at √ s = E d σ d p = C π ( n − )( n − ) nT [ nT + m ( n − )] (cid:18) + m T − mnT (cid:19) − n , (2)which describes the cross section over the whole measured transverse momentum range, as demonstratedin the lower panel of the figure. The parameters m and m T = (cid:112) m + p T correspond to the particle massand the transverse mass, respectively, while C , T and n are the free parameters of the Levy-Tsallisfunction. 8roduction of ω mesons in pp collisions at √ s = ) c (GeV/ T p ) c - ( pb G e V p d s d E p - p + p fi w data: norm. unc. 3.5%Tsallis fitPYTHIA 8.2 Monash 2013PYTHIA 8.2 Tune4CNLO broken SU(3) model p £ m £ /2 p ALICE = 7 TeV s pp, ) c (GeV/ T p T sa lli s f i t d a t a , t h e o r y Fig. 3:
Invariant cross section of ω meson production in pp collisions at √ s = µ , which was used for factorisation, renormalisation and fragmentation.In the bottom panel, the ratios of the theoretical estimates to the Levy-Tsallis fit of the measurement are shown;the ratio of the data to the Levy-Tsallis fit is also presented. Table 2:
Parameters and χ /NDF of the fit to the ω invariant cross section using the Levy-Tsallis function [46]from Eq. 2. Levy-Tsallis C ( × pb) T (GeV) n χ /NDF NDF ω . ± .
47 (stat) ± .
41 (tot) . ± .
042 (stat) ± .
061 (tot) . ± .
37 (stat) ± .
55 (tot) 0 .
45 (stat)0 .
22 (tot) The values of the fit parameters and the reduced χ of the fit are given in Tab. 2, where the fit wasobtained using only statistical uncertainties, and using the systematic and statistical uncertainties of themeasurement added in quadrature. To account for finite p T -interval width, the combined cross sectionpoints were assigned to p T values shifted from the bin centre of the p T intervals according to the under-lying spectrum [47] described by a Levy-Tsallis function. This correction resulted in a shift below 2%in each p T interval. 9roduction of ω mesons in pp collisions at √ s = ) c (GeV/ T p D a t a / T sa lli s f i t ALICE = 7 TeV s pp, p - p + p fi w PCMPHOSEMCPCM-EMC
Fig. 4:
Ratios of the fully corrected ω spectra obtained with the individual reconstruction methods to the Levy-Tsallis fit of the combined spectrum, where the fit parameters are shown in Tab. 2. The statistical and systematicuncertainties are represented by vertical bars and boxes, respectively. The measured differential cross section of ω production is compared to several calculations in Fig. 3.The ratio of each prediction to the Levy-Tsallis fit of the measurement is shown in the bottom panel of thefigure. Two PYTHIA 8.2 [43] Monte Carlo event generator calculations were considered for comparison,which are based on the Monash 2013 [44] and the 4C [45] tunes, respectively. The Monash 2013 tunedescribes the measurement over the full reported p T range within the uncertainties, while the Tune 4Coverestimates the data by about 50%. The Monash 2013 tune includes more recent experimental resultsthan Tune 4C and thus a more refined set of parameters. In particular, the rate of light flavor vectormeson production used in hadronisation process was revised and lowered, improving the description of ω meson yields [44].The measurement is also compared to a next-to-leading order (NLO) calculation using a model withbroken SU(3) symmetry to describe vector meson production [14], where the model parameters havebeen constrained using ω production data measured by PHENIX in pp collisions at √ s =
200 GeV [16].The same scale µ = p T was used for factorisation, renormalisation and fragmentation for the calculationand the shaded band reported in Fig. 3 denotes the scale variation of p T2 / ≤ µ ≤ p T2 . The calculationdescribes the measurement within the uncertainties below 6 GeV / c , and overestimates the data by up to50% for higher p T .The ratio of ω relative to π meson production is shown as a function of p T in Fig. 5, where data points forthe π measurement were taken from Ref. [6]. The ratio is observed to be constant above 2 . / c witha value of C ω / π = . ± .
03 (stat) ± .
04 (sys) . Within the uncertainties, the ω / π ratio is describedby the PYTHIA predictions. Even though the Tune 4C overestimates the ω production, it describes the ω / π ratio due to a similar overestimation of π production, which was reported in Ref. [8].The measured ω / π ratio at √ s = √ s =
62 [15] and 200 GeV [16–18]. The ω / π ratios measured at the different collision energies agree withinthe uncertainties. In order to test the validity of m T -scaling, the Levy-Tsallis parametrisation f π ( p T, π ) of the π spectrum reported in Ref. [6] was scaled using the ratio C ω / π = .
67, following the procedurediscussed in detail in Ref. [20]. The scaled parametrisation f ω ( p T, ω ) was used to calculate the ω / π ratiovia f ω ( p T, ω ) / f π ( p T, ω ) , where the relation p T, ω + m , ω = p T, π + m , π was used to ensure the evaluationof both spectra at the same transverse mass. The obtained m T -scaling prediction of the ω / π ratio isshown in Fig. 5 and found to be consistent with the measurement. Unlike in the case of the η / π ratio10roduction of ω mesons in pp collisions at √ s = ) c (GeV/ T p p / w = 7 TeV, ALICEs ,pp p - p + p fiw p -scaled T m from w PYTHIA 8.2 Monash 2013PYTHIA 8.2 Tune 4C p - p + p fiw g p fiw - e + e fiw g p fiw = 200 GeV, PHENIXs,pp = 200 GeV, PHENIXs,pp = 200 GeV, PHENIXs,pp = 62 GeV, ISRs,pp Fig. 5:
Ratio of ω / π production as a function of transverse momentum p T for pp collisions at √ s = √ s = −
200 GeV [15–18] (gray). In addition,PYTHIA predictions at √ s = ω / π ratio obtained from m T -scaling are shown with lines. measured at √ s = .
76, 7 and 8 TeV [6, 8, 33], where a violation of m T -scaling was observed below3 . ω meson in the entire measuredmomentum range. However, while the measurement is compatible with the m T -scaling prediction at low- p T , the sensitivity of the measurement to a possible m T -scaling violation is limited by the uncertaintiesand p T reach. Here, future studies with increased precision could provide further insights and morestringent tests of m T -scaling for low- p T ω mesons. Interestingly, the PYTHIA calculations and the m T -scaled prediction both describe the ω / π ratio at lower collision energies even below p T = / c ,suggesting a universal feature of meson production. The invariant differential cross section of ω meson production at midrapidity in pp collisions √ s = / c .Within the uncertainties, PYTHIA 8.2 predictions for the Monash 2013 tune describes the measure-ment over the whole p T range, while Tune 4C overestimates the data by about 50%. A NLO calculationusing a model dedicated to describing fragmentation into the entire vector meson nonet describes thedata below 6 GeV / c , while it overestimates the data by up to 50% at higher p T . Above 2 . / c the ω / π ratio is found to be constant with a value of C ω / π = . ± .
03 (stat) ± .
04 (sys) and agreeswith measurements at lower collision energies and with PYTHIA predictions over the whole reported p T range. Within the uncertainties, the m T -scaling prediction for ω mesons is consistent with the mea-sured spectrum above 2 GeV / c . Acknowledgments
We thank D. Indumathi for providing the NLO calculations.The ALICE Collaboration would like to thank all its engineers and technicians for their invaluable con-tributions to the construction of the experiment and the CERN accelerator teams for the outstandingperformance of the LHC complex. The ALICE Collaboration gratefully acknowledges the resources andsupport provided by all Grid centres and the Worldwide LHC Computing Grid (WLCG) collaboration.The ALICE Collaboration acknowledges the following funding agencies for their support in building11roduction of ω mesons in pp collisions at √ s = References [1] D. J. Gross and F. Wilczek, “Asymptotically free Gauge theories,”
Phys. Rev. D8 (1973)3633–3652.[2] J. C. Collins, D. E. Soper, and G. F. Sterman, “Factorization of Hard Processes in QCD,” Adv. Ser. ω mesons in pp collisions at √ s = Direct. High Energy Phys. (1989) 1–91, arXiv:hep-ph/0409313 [hep-ph] .[3] J. C. Collins and D. E. Soper, “Parton Distribution and Decay Functions,” Nucl. Phys.
B194 (1982) 445–492.[4] R. D. Field and R. P. Feynman, “A Parametrization of the Properties of Quark Jets,”
Nucl. Phys.
B136 (1978) 1–76.[5] J. Gao, L. Harland-Lang, and J. Rojo, “The Structure of the Proton in the LHC Precision Era,”
Phys. Rept. (2018) 1–121, arXiv:1709.04922 [hep-ph] .[6]
ALICE
Collaboration, B. Abelev et al. , “Neutral pion and η meson production in proton-protoncollisions at √ s = . √ s = Phys. Lett.
B717 (2012) 162–172, arXiv:1205.5724 [hep-ex] .[7]
ALICE
Collaboration, B. Abelev et al. , “Neutral pion production at midrapidity in pp and Pb–Pbcollisions at √ s NN = .
76 TeV,”
Eur. Phys. J.
C74 (2014) 3108, arXiv:1405.3794 [nucl-ex] .[8]
ALICE
Collaboration, S. Acharya et al. , “ π and η meson production in proton-proton collisionsat √ s = Eur. Phys. J.
C78 no. 3, (2018) 263, arXiv:1708.08745 [hep-ex] .[9] D. de Florian, R. Sassot, M. Epele, R. J. Hernández-Pinto, and M. Stratmann, “Parton-to-pionfragmentation reloaded,”
Phys. Rev.
D91 (2015) 014035, arXiv:1410.6027 [hep-ph] .[10]
Particle Data Group
Collaboration, M. Tanabashi et al. , “Review of particle physics,”
Phys.Rev.D no. 3, (2018) 030001.[11] S. Albino, “The Hadronization of partons,” Rev. Mod. Phys. (2010) 2489–2556, arXiv:0810.4255 [hep-ph] .[12] NNPDF
Collaboration, V. Bertone, S. Carrazza, N. P. Hartland, E. R. Nocera, and J. Rojo, “Adetermination of the fragmentation functions of pions, kaons, and protons with faithfuluncertainties,”
Eur. Phys. J.
C77 no. 8, (2017) 516, arXiv:1706.07049 [hep-ph] .[13] H. Saveetha, D. Indumathi, and S. Mitra, “Vector meson fragmentation using a model with brokenSU(3) at the Next-to-Leading Order,”
Int. J. Mod. Phys.
A29 no. 07, (2014) 1450049, arXiv:1309.2134 [hep-ph] .[14] H. Saveetha and D. Indumathi, “Fragmentation of ω and φ Mesons in e + e − and pp Collisions atNLO,”
Int. J. Mod. Phys.
A32 no. 33, (2017) 1750199, arXiv:1705.00214 [hep-ph] .[15] D. Diakonou et al. , “Inclusive high- p T ω and η (cid:48) production at the ISR,” Physics Letters B no. 3, (1980) 432 – 436.[16] PHENIX
Collaboration, A. Adare et al. , “Measurement of neutral mesons in pp collisions at √ s =200 GeV and scaling properties of hadron production,” Phys. Rev.
D83 (2011) 052004, arXiv:1005.3674 [hep-ex] .[17]
PHENIX
Collaboration, A. Adare et al. , “Production of ω mesons in pp , d–Au, Cu–Cu, andAu–Au collisions at √ s NN = 200 GeV,” Phys. Rev.
C84 (2011) 044902, arXiv:1105.3467[nucl-ex] .[18]
PHENIX
Collaboration, S. S. Adler et al. , “Production of ω mesons at Large TransverseMomenta in pp and d–Au Collisions at √ s NN = 200 GeV,” Phys. Rev.
C75 (2007) 051902, arXiv:nucl-ex/0611031 [nucl-ex] . 13roduction of ω mesons in pp collisions at √ s = ALICE
Collaboration, B. Abelev et al. , “Light vector meson production in pp collisions at √ s = Phys. Lett.
B710 (2012) 557–568, arXiv:1112.2222 [nucl-ex] .[20] L. Altenkämper, F. Bock, C. Loizides, and N. Schmidt, “Applicability of transverse mass scalingin hadronic collisions at energies available at the CERN Large Hadron Collider,”
Phys. Rev.
C96 no. 6, (2017) 064907, arXiv:1710.01933 [hep-ph] .[21] P. K. Khandai, P. Shukla, and V. Singh, “Meson spectra and m T scaling in pp , d –Au, and Au–Aucollisions at √ s NN =
200 GeV,”
Phys. Rev.
C84 (2011) 054904, arXiv:1110.3929 [hep-ph] .[22]
ALICE
Collaboration,
ALICE Inner Tracking System (ITS): Technical Design Report . TechnicalDesign Report ALICE. CERN, Geneva, 1999. http://cds.cern.ch/record/391175 .[23] J. Alme et al. , “The ALICE TPC, a large 3-dimensional tracking device with fast readout forultra-high multiplicity events,”
Nucl. Instrum. Meth.
A622 (2010) 316–367, arXiv:1001.1950[physics.ins-det] .[24]
ALICE
Collaboration, P. Cortese et al. , ALICE Electromagnetic Calorimeter Technical DesignReport . No. CERN-LHCC-2008-014. ALICE-TDR-14. Aug, 2008. https://cds.cern.ch/record/1121574 .[25]
ALICE EMCal
Collaboration, U. Abeysekara et al. , “ALICE EMCal physics performancereport,” arXiv:1008.0413 [physics.ins-det] .[26]
ALICE
Collaboration, V. I. Man’ko, W. Klempt, L. Leistam, J. De Groot, and J. Schükraft,
ALICE Photon Spectrometer (PHOS): Technical Design Report . Technical Design Report ALICE.CERN, Geneva, 1999. https://cds.cern.ch/record/381432 .[27]
ALICE
Collaboration, B. Abelev et al. , “Performance of the ALICE experiment at the CERNLHC,”
Int. J. Mod. Phys.
A29 (2014) 1430044, arXiv:1402.4476 [nucl-ex] .[28]
ALICE
Collaboration, K. Aamodt et al. , “The ALICE experiment at the CERN LHC,”
JINST (2008) S08002.[29] ALICE
Collaboration, E. Abbas et al. , “Performance of the ALICE VZERO system,”
JINST (2013) P10016, arXiv:1306.3130 [nucl-ex] .[30] ALICE
Collaboration, S. Acharya et al. , “Calibration of the photon spectrometer PHOS of theALICE experiment,”
JINST no. 05, (2019) P05025, arXiv:1902.06145[physics.ins-det] .[31] ALICE
Collaboration, B. Abelev et al. , “Measurement of inelastic, single- and double-diffractioncross sections in proton–proton collisions at the LHC with ALICE,”
Eur. Phys. J.
C73 (2013)2456, arXiv:1208.4968 [hep-ex] .[32]
ALICE
Collaboration, J. Adam et al. , “Measurement of pion, kaon and proton production inproton–proton collisions at √ s = Eur. Phys. J.
C75 no. 5, (2015) 226, arXiv:1504.00024 [nucl-ex] .[33]
ALICE
Collaboration, S. Acharya et al. , “Production of π and η mesons up to high transversemomentum in pp collisions at 2.76 TeV,” Eur. Phys. J.
C77 no. 5, (2017) 339, arXiv:1702.00917 [hep-ex] .[34] T. Awes, F. Obenshain, F. Plasil, S. Saini, S. Sorensen, and G. Young, “A simple method of showerlocalization and identification in laterally segmented calorimeters,”
Nucl. Instrum. Meth.
A311 no. 1–2, (1992) 130 – 138. 14roduction of ω mesons in pp collisions at √ s = ALICE
Collaboration, C. W. Fabjan et al. , “ALICE: Physics performance report, volume II,”
J.Phys.
G32 (2006) 1295–2040.[36] J. Podolanski and R. Armenteros, “III. Analysis of V-events,”
Phil. Mag. no. 360, (1954) 13–30.[37] ALICE
Collaboration, “Production of ω ( ) in pp collisions at √ s = 7 TeV,” (2018) . https://cds.cern.ch/record/2316785 .[38] T. Sjostrand, S. Mrenna, and P. Z. Skands, “PYTHIA 6.4 physics and manual,” JHEP (2006)026, arXiv:hep-ph/0603175 [hep-ph] .[39] M. Stevenson, L. Alvarez, B. Maglic, and A. Rosenfeld, “Spin and Parity of the omega Meson,” Phys. Rev. (1962) 687–690.[40] J. Danburg, M. Abolins, O. Dahl, D. Davies, P. Hoch, J. Kirz, D. H. Miller, and R. Rader,“Production and decay of eta and omega mesons in the reaction π + d → ( p ) p π + π − π between 1.1and 2.4 GeV/ c ,” Phys. Rev. D (1970) 2564–2588.[41] R. Brun, F. Carminati, and S. Giani, “GEANT Detector Description and Simulation Tool,” CERNProgram Library Long Write-up, W5013 (1994) .[42] A. Valassi and R. Chierici, “Information and treatment of unknown correlations in thecombination of measurements using the BLUE method,”
Eur. Phys. J.
C74 (2014) 2717, arXiv:1307.4003 [physics.data-an] .[43] T. Sjöstrand, S. Ask, J. R. Christiansen, R. Corke, N. Desai, P. Ilten, S. Mrenna, S. Prestel, C. O.Rasmussen, and P. Z. Skands, “An Introduction to PYTHIA 8.2,”
Comput. Phys. Commun. (2015) 159–177, arXiv:1410.3012 [hep-ph] .[44] P. Skands, S. Carrazza, and J. Rojo, “Tuning PYTHIA 8.1: the Monash 2013 Tune,”
Eur. Phys. J.
C74 (2014) 3024, arXiv:1404.5630 [hep-ph] .[45] R. Corke and T. Sjostrand, “Interleaved Parton Showers and Tuning Prospects,”
JHEP (2011)032, arXiv:1011.1759 [hep-ph] .[46] C. Tsallis, “Possible generalization of Boltzmann-Gibbs statistics,” J. Statist. Phys. (1988)479–487.[47] G. D. Lafferty and T. R. Wyatt, “Where to stick your data points: The treatment of measurementswithin wide bins,” Nucl. Instrum. Meth.
A355 (1995) 541–547.15roduction of ω mesons in pp collisions at √ s = A The ALICE Collaboration
S. Acharya , D. Adamová , A. Adler , J. Adolfsson , M.M. Aggarwal , S. Agha , G. Aglieri Rinella ,M. Agnello , N. Agrawal
10 ,54 , Z. Ahammed , S. Ahmad , S.U. Ahn , Z. Akbar , A. Akindinov ,M. Al-Turany , S.N. Alam , D.S.D. Albuquerque , D. Aleksandrov , B. Alessandro , H.M. Alfanda ,R. Alfaro Molina , B. Ali , Y. Ali , A. Alici
10 ,26 ,54 , N. Alizadehvandchali , A. Alkin , J. Alme ,T. Alt , L. Altenkamper , I. Altsybeev , M.N. Anaam , C. Andrei , D. Andreou , A. Andronic ,M. Angeletti , V. Anguelov , T. Antiˇci´c , F. Antinori , P. Antonioli , N. Apadula , L. Aphecetche ,H. Appelshäuser , S. Arcelli , R. Arnaldi , M. Arratia , I.C. Arsene , M. Arslandok , A. Augustinus ,R. Averbeck , S. Aziz , M.D. Azmi , A. Badalà , Y.W. Baek , S. Bagnasco , X. Bai ,R. Bailhache , R. Bala , A. Balbino , A. Baldisseri , M. Ball , S. Balouza , D. Banerjee ,R. Barbera , L. Barioglio , G.G. Barnaföldi , L.S. Barnby , V. Barret , P. Bartalini , C. Bartels ,K. Barth , E. Bartsch , F. Baruffaldi , N. Bastid , S. Basu , G. Batigne , B. Batyunya , D. Bauri ,J.L. Bazo Alba , I.G. Bearden , C. Beattie , C. Bedda , I. Belikov , A.D.C. Bell Hechavarria ,F. Bellini , R. Bellwied , V. Belyaev , G. Bencedi , S. Beole , A. Bercuci , Y. Berdnikov ,D. Berenyi , R.A. Bertens , D. Berzano , M.G. Besoiu , L. Betev , A. Bhasin , I.R. Bhat ,M.A. Bhat , H. Bhatt , B. Bhattacharjee , A. Bianchi , L. Bianchi , N. Bianchi , J. Bielˇcík ,J. Bielˇcíková , A. Bilandzic , G. Biro , R. Biswas , S. Biswas , J.T. Blair , D. Blau , C. Blume ,G. Boca , F. Bock , A. Bogdanov , S. Boi , J. Bok , L. Boldizsár , A. Bolozdynya , M. Bombara ,G. Bonomi , H. Borel , A. Borissov , H. Bossi , E. Botta , L. Bratrud , P. Braun-Munzinger ,M. Bregant , M. Broz , E. Bruna , G.E. Bruno
33 ,106 , M.D. Buckland , D. Budnikov , H. Buesching ,S. Bufalino , O. Bugnon , P. Buhler , P. Buncic , Z. Buthelezi
72 ,131 , J.B. Butt , S.A. Bysiak ,D. Caffarri , A. Caliva , E. Calvo Villar , J.M.M. Camacho , R.S. Camacho , P. Camerini ,F.D.M. Canedo , A.A. Capon , F. Carnesecchi , R. Caron , J. Castillo Castellanos , A.J. Castro ,E.A.R. Casula , F. Catalano , C. Ceballos Sanchez , P. Chakraborty , S. Chandra , W. Chang ,S. Chapeland , M. Chartier , S. Chattopadhyay , S. Chattopadhyay , A. Chauvin , C. Cheshkov ,B. Cheynis , V. Chibante Barroso , D.D. Chinellato , S. Cho , P. Chochula , T. Chowdhury ,P. Christakoglou , C.H. Christensen , P. Christiansen , T. Chujo , C. Cicalo , L. Cifarelli
10 ,26 ,F. Cindolo , M.R. Ciupek , G. Clai
54 ,ii , J. Cleymans , F. Colamaria , D. Colella , A. Collu ,M. Colocci , M. Concas
59 ,iii , G. Conesa Balbastre , Z. Conesa del Valle , G. Contin
24 ,60 , J.G. Contreras ,T.M. Cormier , Y. Corrales Morales , P. Cortese , M.R. Cosentino , F. Costa , S. Costanza ,P. Crochet , E. Cuautle , P. Cui , L. Cunqueiro , D. Dabrowski , T. Dahms , A. Dainese ,F.P.A. Damas
115 ,137 , M.C. Danisch , A. Danu , D. Das , I. Das , P. Das , P. Das , S. Das ,A. Dash , S. Dash , S. De , A. De Caro , G. de Cataldo , L. De Cilladi , J. de Cuveland , A. DeFalco , D. De Gruttola , N. De Marco , C. De Martin , S. De Pasquale , S. Deb , H.F. Degenhardt ,K.R. Deja , A. Deloff , S. Delsanto
25 ,131 , W. Deng , P. Dhankher , D. Di Bari , A. Di Mauro ,R.A. Diaz , T. Dietel , P. Dillenseger , Y. Ding , R. Divià , D.U. Dixit , Ø. Djuvsland , U. Dmitrieva ,A. Dobrin , B. Dönigus , O. Dordic , A.K. Dubey , A. Dubla
90 ,107 , S. Dudi , M. Dukhishyam ,P. Dupieux , R.J. Ehlers , V.N. Eikeland , D. Elia , B. Erazmus , F. Erhardt , A. Erokhin ,M.R. Ersdal , B. Espagnon , G. Eulisse , D. Evans , S. Evdokimov , L. Fabbietti , M. Faggin ,J. Faivre , F. Fan , A. Fantoni , M. Fasel , P. Fecchio , A. Feliciello , G. Feofilov , A. FernándezTéllez , A. Ferrero , A. Ferretti , A. Festanti , V.J.G. Feuillard , J. Figiel , S. Filchagin ,D. Finogeev , F.M. Fionda , G. Fiorenza , F. Flor , A.N. Flores , S. Foertsch , P. Foka , S. Fokin ,E. Fragiacomo , U. Frankenfeld , U. Fuchs , C. Furget , A. Furs , M. Fusco Girard , J.J. Gaardhøje ,M. Gagliardi , A.M. Gago , A. Gal , C.D. Galvan , P. Ganoti , C. Garabatos , J.R.A. Garcia ,E. Garcia-Solis , K. Garg , C. Gargiulo , A. Garibli , K. Garner , P. Gasik
105 ,107 , E.F. Gauger ,M.B. Gay Ducati , M. Germain , J. Ghosh , P. Ghosh , S.K. Ghosh , M. Giacalone , P. Gianotti ,P. Giubellino
59 ,107 , P. Giubilato , A.M.C. Glaenzer , P. Glässel , A. Gomez Ramirez ,V. Gonzalez
107 ,143 , L.H. González-Trueba , S. Gorbunov , L. Görlich , A. Goswami , S. Gotovac ,V. Grabski , L.K. Graczykowski , K.L. Graham , L. Greiner , A. Grelli , C. Grigoras , V. Grigoriev ,A. Grigoryan , S. Grigoryan , O.S. Groettvik , F. Grosa
30 ,59 , J.F. Grosse-Oetringhaus , R. Grosso ,R. Guernane , M. Guittiere , K. Gulbrandsen , T. Gunji , A. Gupta , R. Gupta , I.B. Guzman ,R. Haake , M.K. Habib , C. Hadjidakis , H. Hamagaki , G. Hamar , M. Hamid , R. Hannigan ,M.R. Haque , A. Harlenderova , J.W. Harris , A. Harton , J.A. Hasenbichler , H. Hassan ,Q.U. Hassan , D. Hatzifotiadou
10 ,54 , P. Hauer , L.B. Havener , S. Hayashi , S.T. Heckel ,E. Hellbär , H. Helstrup , A. Herghelegiu , T. Herman , E.G. Hernandez , G. Herrera Corral ,F. Herrmann , K.F. Hetland , H. Hillemanns , C. Hills , B. Hippolyte , B. Hohlweger , ω mesons in pp collisions at √ s = J. Honermann , D. Horak , A. Hornung , S. Hornung , R. Hosokawa
15 ,133 , P. Hristov , C. Huang ,C. Hughes , P. Huhn , T.J. Humanic , H. Hushnud , L.A. Husova , N. Hussain , S.A. Hussain ,D. Hutter , J.P. Iddon
34 ,127 , R. Ilkaev , H. Ilyas , M. Inaba , G.M. Innocenti , M. Ippolitov ,A. Isakov , M.S. Islam , M. Ivanov , V. Ivanov , V. Izucheev , B. Jacak , N. Jacazio
34 ,54 ,P.M. Jacobs , S. Jadlovska , J. Jadlovsky , S. Jaelani , C. Jahnke , M.J. Jakubowska ,M.A. Janik , T. Janson , M. Jercic , O. Jevons , M. Jin , F. Jonas
96 ,144 , P.G. Jones , J. Jung ,M. Jung , A. Jusko , P. Kalinak , A. Kalweit , V. Kaplin , S. Kar , A. Karasu Uysal , D. Karatovic ,O. Karavichev , T. Karavicheva , P. Karczmarczyk , E. Karpechev , A. Kazantsev , U. Kebschull ,R. Keidel , M. Keil , B. Ketzer , Z. Khabanova , A.M. Khan , S. Khan , A. Khanzadeev ,Y. Kharlov , A. Khatun , A. Khuntia , B. Kileng , B. Kim , B. Kim , D. Kim , D.J. Kim ,E.J. Kim , H. Kim , J. Kim , J.S. Kim , J. Kim , J. Kim , J. Kim , M. Kim , S. Kim ,T. Kim , T. Kim , S. Kirsch , I. Kisel , S. Kiselev , A. Kisiel , J.L. Klay , C. Klein , J. Klein
34 ,59 ,S. Klein , C. Klein-Bösing , M. Kleiner , T. Klemenz , A. Kluge , M.L. Knichel , A.G. Knospe ,C. Kobdaj , M.K. Köhler , T. Kollegger , A. Kondratyev , N. Kondratyeva , E. Kondratyuk ,J. Konig , S.A. Konigstorfer , P.J. Konopka , G. Kornakov , L. Koska , O. Kovalenko ,V. Kovalenko , M. Kowalski , I. Králik , A. Kravˇcáková , L. Kreis , M. Krivda
64 ,111 , F. Krizek ,K. Krizkova Gajdosova , M. Krüger , E. Kryshen , M. Krzewicki , A.M. Kubera , V. Kuˇcera
34 ,61 ,C. Kuhn , P.G. Kuijer , L. Kumar , S. Kundu , P. Kurashvili , A. Kurepin , A.B. Kurepin ,A. Kuryakin , S. Kushpil , J. Kvapil , M.J. Kweon , J.Y. Kwon , Y. Kwon , S.L. La Pointe , P. LaRocca , Y.S. Lai , A. Lakrathok , M. Lamanna , R. Langoy , K. Lapidus , A. Lardeux ,P. Larionov , E. Laudi , R. Lavicka , T. Lazareva , R. Lea , L. Leardini , J. Lee , S. Lee ,S. Lehner , J. Lehrbach , R.C. Lemmon , I. León Monzón , E.D. Lesser , M. Lettrich , P. Lévai ,X. Li , X.L. Li , J. Lien , R. Lietava , B. Lim , V. Lindenstruth , A. Lindner , C. Lippmann ,M.A. Lisa , A. Liu , J. Liu , S. Liu , W.J. Llope , I.M. Lofnes , V. Loginov , C. Loizides ,P. Loncar , J.A. Lopez , X. Lopez , E. López Torres , J.R. Luhder , M. Lunardon , G. Luparello ,Y.G. Ma , A. Maevskaya , M. Mager , S.M. Mahmood , T. Mahmoud , A. Maire , R.D. Majka
146 ,i ,M. Malaev , Q.W. Malik , L. Malinina
75 ,iv , D. Mal’Kevich , P. Malzacher , G. Mandaglio
32 ,56 ,V. Manko , F. Manso , V. Manzari , Y. Mao , M. Marchisone , J. Mareš , G.V. Margagliotti ,A. Margotti , A. Marín , C. Markert , M. Marquard , N.A. Martin , P. Martinengo , J.L. Martinez ,M.I. Martínez , G. Martínez García , S. Masciocchi , M. Masera , A. Masoni , L. Massacrier ,E. Masson , A. Mastroserio
53 ,138 , A.M. Mathis , O. Matonoha , P.F.T. Matuoka , A. Matyja ,C. Mayer , F. Mazzaschi , M. Mazzilli , M.A. Mazzoni , A.F. Mechler , F. Meddi , Y. Melikyan
62 ,93 ,A. Menchaca-Rocha , C. Mengke , E. Meninno
29 ,114 , A.S. Menon , M. Meres , S. Mhlanga ,Y. Miake , L. Micheletti , L.C. Migliorin , D.L. Mihaylov , K. Mikhaylov
75 ,92 , A.N. Mishra ,D. Mi´skowiec , A. Modak , N. Mohammadi , A.P. Mohanty , B. Mohanty , M. Mohisin Khan
16 ,v ,Z. Moravcova , C. Mordasini , D.A. Moreira De Godoy , L.A.P. Moreno , I. Morozov , A. Morsch ,T. Mrnjavac , V. Muccifora , E. Mudnic , D. Mühlheim , S. Muhuri , J.D. Mulligan , A. Mulliri
23 ,55 ,M.G. Munhoz , R.H. Munzer , H. Murakami , S. Murray , L. Musa , J. Musinsky , C.J. Myers ,J.W. Myrcha , B. Naik , R. Nair , B.K. Nandi , R. Nania
10 ,54 , E. Nappi , M.U. Naru ,A.F. Nassirpour , C. Nattrass , R. Nayak , T.K. Nayak , S. Nazarenko , A. Neagu , R.A. Negrao DeOliveira , L. Nellen , S.V. Nesbo , G. Neskovic , D. Nesterov , L.T. Neumann , B.S. Nielsen ,S. Nikolaev , S. Nikulin , V. Nikulin , F. Noferini
10 ,54 , P. Nomokonov , J. Norman
79 ,127 , N. Novitzky ,P. Nowakowski , A. Nyanin , J. Nystrand , M. Ogino , A. Ohlson , J. Oleniacz , A.C. Oliveira DaSilva , M.H. Oliver , C. Oppedisano , A. Ortiz Velasquez , T. Osako , A. Oskarsson ,J. Otwinowski , K. Oyama , Y. Pachmayer , V. Pacik , S. Padhan , D. Pagano , G. Pai´c , J. Pan ,S. Panebianco , P. Pareek
50 ,141 , J. Park , J.E. Parkkila , S. Parmar , S.P. Pathak , B. Paul ,J. Pazzini , H. Pei , T. Peitzmann , X. Peng , L.G. Pereira , H. Pereira Da Costa , D. Peresunko ,G.M. Perez , S. Perrin , Y. Pestov , V. Petráˇcek , M. Petrovici , R.P. Pezzi , S. Piano , M. Pikna ,P. Pillot , O. Pinazza
34 ,54 , L. Pinsky , C. Pinto , S. Pisano
10 ,52 , D. Pistone , M. Płosko´n ,M. Planinic , F. Pliquett , M.G. Poghosyan , B. Polichtchouk , N. Poljak , A. Pop ,S. Porteboeuf-Houssais , V. Pozdniakov , S.K. Prasad , R. Preghenella , F. Prino , C.A. Pruneau ,I. Pshenichnov , M. Puccio , J. Putschke , S. Qiu , L. Quaglia , R.E. Quishpe , S. Ragoni ,S. Raha , S. Rajput , J. Rak , A. Rakotozafindrabe , L. Ramello , F. Rami , S.A.R. Ramirez ,R. Raniwala , S. Raniwala , S.S. Räsänen , R. Rath , V. Ratza , I. Ravasenga , K.F. Read
96 ,130 ,A.R. Redelbach , K. Redlich
85 ,vi , A. Rehman , P. Reichelt , F. Reidt , X. Ren , R. Renfordt ,Z. Rescakova , K. Reygers , A. Riabov , V. Riabov , T. Richert
81 ,89 , M. Richter , P. Riedler , ω mesons in pp collisions at √ s = W. Riegler , F. Riggi , C. Ristea , S.P. Rode , M. Rodríguez Cahuantzi , K. Røed , R. Rogalev ,E. Rogochaya , D. Rohr , D. Röhrich , P.F. Rojas , P.S. Rokita , F. Ronchetti , A. Rosano ,E.D. Rosas , K. Roslon , A. Rossi , A. Rotondi , A. Roy , P. Roy , O.V. Rueda , R. Rui ,B. Rumyantsev , A. Rustamov , E. Ryabinkin , Y. Ryabov , A. Rybicki , H. Rytkonen ,O.A.M. Saarimaki , R. Sadek , S. Sadhu , S. Sadovsky , K. Šafaˇrík , S.K. Saha , B. Sahoo ,P. Sahoo , R. Sahoo , S. Sahoo , P.K. Sahu , J. Saini , S. Sakai , S. Sambyal , V. Samsonov
93 ,98 ,D. Sarkar , N. Sarkar , P. Sarma , V.M. Sarti , M.H.P. Sas , E. Scapparone , J. Schambach ,H.S. Scheid , C. Schiaua , R. Schicker , A. Schmah , C. Schmidt , H.R. Schmidt ,M.O. Schmidt , M. Schmidt , N.V. Schmidt
68 ,96 , A.R. Schmier , J. Schukraft , Y. Schutz ,K. Schwarz , K. Schweda , G. Scioli , E. Scomparin , J.E. Seger , Y. Sekiguchi , D. Sekihata ,I. Selyuzhenkov
93 ,107 , S. Senyukov , D. Serebryakov , A. Sevcenco , A. Shabanov , A. Shabetai ,R. Shahoyan , W. Shaikh , A. Shangaraev , A. Sharma , A. Sharma , H. Sharma , M. Sharma ,N. Sharma , S. Sharma , O. Sheibani , K. Shigaki , M. Shimomura , S. Shirinkin , Q. Shou ,Y. Sibiriak , S. Siddhanta , T. Siemiarczuk , D. Silvermyr , G. Simatovic , G. Simonetti , B. Singh ,R. Singh , R. Singh , R. Singh , V.K. Singh , V. Singhal , T. Sinha , B. Sitar , M. Sitta ,T.B. Skaali , M. Slupecki , N. Smirnov , R.J.M. Snellings , C. Soncco , J. Song ,A. Songmoolnak , F. Soramel , S. Sorensen , I. Sputowska , J. Stachel , I. Stan , P.J. Steffanic ,E. Stenlund , S.F. Stiefelmaier , D. Stocco , M.M. Storetvedt , L.D. Stritto , A.A.P. Suaide ,T. Sugitate , C. Suire , M. Suleymanov , M. Suljic , R. Sultanov , M. Šumbera , V. Sumberia ,S. Sumowidagdo , S. Swain , A. Szabo , I. Szarka , U. Tabassam , S.F. Taghavi , G. Taillepied ,J. Takahashi , G.J. Tambave , S. Tang , M. Tarhini , M.G. Tarzila , A. Tauro , G. Tejeda Muñoz ,A. Telesca , L. Terlizzi , C. Terrevoli , D. Thakur , S. Thakur , D. Thomas , F. Thoresen ,R. Tieulent , A. Tikhonov , A.R. Timmins , A. Toia , N. Topilskaya , M. Toppi , F. Torales-Acosta ,S.R. Torres , A. Trifiró
32 ,56 , S. Tripathy
50 ,69 , T. Tripathy , S. Trogolo , G. Trombetta , L. Tropp ,V. Trubnikov , W.H. Trzaska , T.P. Trzcinski , B.A. Trzeciak
37 ,63 , A. Tumkin , R. Turrisi ,T.S. Tveter , K. Ullaland , E.N. Umaka , A. Uras , G.L. Usai , M. Vala , N. Valle , S. Vallero ,N. van der Kolk , L.V.R. van Doremalen , M. van Leeuwen , P. Vande Vyvre , D. Varga , Z. Varga ,M. Varga-Kofarago , A. Vargas , M. Vasileiou , A. Vasiliev , O. Vázquez Doce , V. Vechernin ,E. Vercellin , S. Vergara Limón , L. Vermunt , R. Vernet , R. Vértesi , M. Verweij , L. Vickovic ,Z. Vilakazi , O. Villalobos Baillie , G. Vino , A. Vinogradov , T. Virgili , V. Vislavicius ,A. Vodopyanov , B. Volkel , M.A. Völkl , K. Voloshin , S.A. Voloshin , G. Volpe , B. von Haller ,I. Vorobyev , D. Voscek , J. Vrláková , B. Wagner , M. Weber , S.G. Weber , A. Wegrzynek ,S.C. Wenzel , J.P. Wessels , J. Wiechula , J. Wikne , G. Wilk , J. Wilkinson , G.A. Willems ,E. Willsher , B. Windelband , M. Winn , W.E. Witt , J.R. Wright , Y. Wu , R. Xu , S. Yalcin ,Y. Yamaguchi , K. Yamakawa , S. Yang , S. Yano , Z. Yin , H. Yokoyama , I.-K. Yoo , J.H. Yoon ,S. Yuan , A. Yuncu , V. Yurchenko , V. Zaccolo , A. Zaman , C. Zampolli , H.J.C. Zanoli ,N. Zardoshti , A. Zarochentsev , P. Závada , N. Zaviyalov , H. Zbroszczyk , M. Zhalov , S. Zhang ,X. Zhang , Z. Zhang , V. Zherebchevskii , Y. Zhi , D. Zhou , Y. Zhou , Z. Zhou , J. Zhu , Y. Zhu ,A. Zichichi
10 ,26 , G. Zinovjev , N. Zurlo , Affiliation notes i Deceased ii Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA),Bologna, Italy iii
Dipartimento DET del Politecnico di Torino, Turin, Italy iv M.V. Lomonosov Moscow State University, D.V. Skobeltsyn Institute of Nuclear, Physics, Moscow, Russia v Department of Applied Physics, Aligarh Muslim University, Aligarh, India vi Institute of Theoretical Physics, University of Wroclaw, Poland
Collaboration Institutes A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, Yerevan, Armenia Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Kiev, Ukraine Bose Institute, Department of Physics and Centre for Astroparticle Physics and Space Science (CAPSS),Kolkata, India Budker Institute for Nuclear Physics, Novosibirsk, Russia ω mesons in pp collisions at √ s = California Polytechnic State University, San Luis Obispo, California, United States Central China Normal University, Wuhan, China Centre de Calcul de l’IN2P3, Villeurbanne, Lyon, France Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Havana, Cuba Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City and Mérida, Mexico Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi’, Rome, Italy Chicago State University, Chicago, Illinois, United States China Institute of Atomic Energy, Beijing, China Comenius University Bratislava, Faculty of Mathematics, Physics and Informatics, Bratislava, Slovakia COMSATS University Islamabad, Islamabad, Pakistan Creighton University, Omaha, Nebraska, United States Department of Physics, Aligarh Muslim University, Aligarh, India Department of Physics, Pusan National University, Pusan, Republic of Korea Department of Physics, Sejong University, Seoul, Republic of Korea Department of Physics, University of California, Berkeley, California, United States Department of Physics, University of Oslo, Oslo, Norway Department of Physics and Technology, University of Bergen, Bergen, Norway Dipartimento di Fisica dell’Università ’La Sapienza’ and Sezione INFN, Rome, Italy Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Bologna, Italy Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Catania, Italy Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Padova, Italy Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo Collegato INFN, Salerno, Italy Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy Dipartimento di Scienze e Innovazione Tecnologica dell’Università del Piemonte Orientale and INFNSezione di Torino, Alessandria, Italy Dipartimento di Scienze MIFT, Università di Messina, Messina, Italy Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy European Organization for Nuclear Research (CERN), Geneva, Switzerland Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split,Split, Croatia Faculty of Engineering and Science, Western Norway University of Applied Sciences, Bergen, Norway Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague,Czech Republic Faculty of Science, P.J. Šafárik University, Košice, Slovakia Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt,Germany Fudan University, Shanghai, China Gangneung-Wonju National University, Gangneung, Republic of Korea Gauhati University, Department of Physics, Guwahati, India Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn,Germany Helsinki Institute of Physics (HIP), Helsinki, Finland High Energy Physics Group, Universidad Autónoma de Puebla, Puebla, Mexico Hiroshima University, Hiroshima, Japan Hochschule Worms, Zentrum für Technologietransfer und Telekommunikation (ZTT), Worms, Germany Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania Indian Institute of Technology Bombay (IIT), Mumbai, India Indian Institute of Technology Indore, Indore, India Indonesian Institute of Sciences, Jakarta, Indonesia INFN, Laboratori Nazionali di Frascati, Frascati, Italy INFN, Sezione di Bari, Bari, Italy INFN, Sezione di Bologna, Bologna, Italy INFN, Sezione di Cagliari, Cagliari, Italy ω mesons in pp collisions at √ s = INFN, Sezione di Catania, Catania, Italy INFN, Sezione di Padova, Padova, Italy INFN, Sezione di Roma, Rome, Italy INFN, Sezione di Torino, Turin, Italy INFN, Sezione di Trieste, Trieste, Italy Inha University, Incheon, Republic of Korea Institute for Nuclear Research, Academy of Sciences, Moscow, Russia Institute for Subatomic Physics, Utrecht University/Nikhef, Utrecht, Netherlands Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovakia Institute of Physics, Homi Bhabha National Institute, Bhubaneswar, India Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic Institute of Space Science (ISS), Bucharest, Romania Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico City, Mexico Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil Instituto de Física, Universidad Nacional Autónoma de México, Mexico City, Mexico iThemba LABS, National Research Foundation, Somerset West, South Africa Jeonbuk National University, Jeonju, Republic of Korea Johann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik, Fachbereich Informatik undMathematik, Frankfurt, Germany Joint Institute for Nuclear Research (JINR), Dubna, Russia Korea Institute of Science and Technology Information, Daejeon, Republic of Korea KTO Karatay University, Konya, Turkey Laboratoire de Physique des 2 Infinis, Irène Joliot-Curie, Orsay, France Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-Alpes, CNRS-IN2P3,Grenoble, France Lawrence Berkeley National Laboratory, Berkeley, California, United States Lund University Department of Physics, Division of Particle Physics, Lund, Sweden Nagasaki Institute of Applied Science, Nagasaki, Japan Nara Women’s University (NWU), Nara, Japan National and Kapodistrian University of Athens, School of Science, Department of Physics , Athens,Greece National Centre for Nuclear Research, Warsaw, Poland National Institute of Science Education and Research, Homi Bhabha National Institute, Jatni, India National Nuclear Research Center, Baku, Azerbaijan National Research Centre Kurchatov Institute, Moscow, Russia Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark Nikhef, National institute for subatomic physics, Amsterdam, Netherlands NRC Kurchatov Institute IHEP, Protvino, Russia NRC «Kurchatov»Institute - ITEP, Moscow, Russia NRNU Moscow Engineering Physics Institute, Moscow, Russia Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom Nuclear Physics Institute of the Czech Academy of Sciences, ˇRež u Prahy, Czech Republic Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States Ohio State University, Columbus, Ohio, United States Petersburg Nuclear Physics Institute, Gatchina, Russia Physics department, Faculty of science, University of Zagreb, Zagreb, Croatia
Physics Department, Panjab University, Chandigarh, India
Physics Department, University of Jammu, Jammu, India
Physics Department, University of Rajasthan, Jaipur, India
Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
Physik Department, Technische Universität München, Munich, Germany
Politecnico di Bari, Bari, Italy
Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum fürSchwerionenforschung GmbH, Darmstadt, Germany ω mesons in pp collisions at √ s = Rudjer Boškovi´c Institute, Zagreb, Croatia
Russian Federal Nuclear Center (VNIIEF), Sarov, Russia
Saha Institute of Nuclear Physics, Homi Bhabha National Institute, Kolkata, India
School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom
Sección Física, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Lima, Peru
St. Petersburg State University, St. Petersburg, Russia
Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria
SUBATECH, IMT Atlantique, Université de Nantes, CNRS-IN2P3, Nantes, France
Suranaree University of Technology, Nakhon Ratchasima, Thailand
Technical University of Košice, Košice, Slovakia
The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland
The University of Texas at Austin, Austin, Texas, United States
Universidad Autónoma de Sinaloa, Culiacán, Mexico
Universidade de São Paulo (USP), São Paulo, Brazil
Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil
Universidade Federal do ABC, Santo Andre, Brazil
University of Cape Town, Cape Town, South Africa
University of Houston, Houston, Texas, United States
University of Jyväskylä, Jyväskylä, Finland
University of Liverpool, Liverpool, United Kingdom
University of Science and Technology of China, Hefei, China
University of South-Eastern Norway, Tonsberg, Norway
University of Tennessee, Knoxville, Tennessee, United States
University of the Witwatersrand, Johannesburg, South Africa
University of Tokyo, Tokyo, Japan
University of Tsukuba, Tsukuba, Japan
Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France
Université de Lyon, Université Lyon 1, CNRS/IN2P3, IPN-Lyon, Villeurbanne, Lyon, France
Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France, Strasbourg, France
Université Paris-Saclay Centre d’Etudes de Saclay (CEA), IRFU, Départment de Physique Nucléaire(DPhN), Saclay, France
Università degli Studi di Foggia, Foggia, Italy
Università degli Studi di Pavia, Pavia, Italy
Università di Brescia, Brescia, Italy
Variable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata, India
Warsaw University of Technology, Warsaw, Poland
Wayne State University, Detroit, Michigan, United States
Westfälische Wilhelms-Universität Münster, Institut für Kernphysik, Münster, Germany
Wigner Research Centre for Physics, Budapest, Hungary
Yale University, New Haven, Connecticut, United States