DIS2015 Heavy Flavours Working Group Summary
aa r X i v : . [ h e p - ph ] S e p MAN/HEP/2015/16
DIS2015 Heavy Flavours Working Group Summary
Marco Guzzi ∗ Consortium for Fundamental Physics, School of Physics & AstronomyUniversity of Manchester, Manchester, M13 9PL, United KingdomE-mail: [email protected]
Achim Geiser
Deutsches Elektronen-Synchrotron DESY,Notkestrasse 85, 22607 Hamburg, GermanyE-mail: [email protected]
Flera Rizatdinova
Department of Physics, Oklahoma State University,145 Physical Sciences Bldg., Stillwater, OK, USAE-mail:
Studies presented in the heavy flavours working group are summarized. Very recent results ofmeasurements at the HERA, LHC, Tevatron, STAR, PHENIX, and BaBar experiments are re-viewed and new developments in theory and phenomenology are discussed. In particular, aspectsof the impact of heavy flavours on global QCD analyses to determine the structure of the proton,and analyses in physics beyond the Standard Model are considered.
The XXIII International Workshop on Deep Inelastic Scattering and Related SubjectsApril 27 - May 1, 2015Southern Methodist UniversityDallas, Texas 75275 ∗ Speaker. c (cid:13) Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlikeLicence. http://pos.sissa.it/ eavy-flavour Physics Highlights
Marco Guzzi
1. Introduction
Heavy-flavor physics plays a leading role in many areas of collider phenomenology and pro-vides us with powerful tools to handle perturbative and non-perturbative aspects of QCD.Experimental measurements of cross sections for the production of heavy quarks and differentcharmed and beauty hadrons, are extremely important to constrain both the structure of the protonin various kinematic regions and fundamental parameters of the Standard Model (SM), such asquark masses and couplings. Precision in the determination of the parton distribution functions(PDFs) of the proton is crucial for the interpretation of measurements in hadronic collisions. PDFsrepresent a limiting factor in the accuracy of theory predictions for SM processes at the LHC.In this workshop the H1, ZEUS, Tevatron, ATLAS, CMS, and LHCb experiments presented novelmeasurements which are of high importance for the determination of unpolarized PDFs. Moreover,it has been reported about the progress going on on the theoretical side to reach the new state-of-the-art in high-order QCD calculations to determine fully differential cross sections for heavy-flavourproduction at hadron colliders. Heavy-flavour production (in particular production of top-quarkpairs t ¯ t ) has the potential to impose clean constraints on PDFs (gluon) at large x , where they arecurrently weak.Heavy-flavour decays were also extensively discussed, in particular new measurements for theB-meson decay and rare charm and beauty-quark decays were presented by the ATLAS, LHCb,and Babar collaborations. Heavy-flavour decays are important to understand the flavour structureof the SM. At the present time, the SM leaves many open questions about the flavour sector: theorigin of generation and masses, the mixing and disappearance of antimatter. Investigations oncharge and parity (CP) violations in hadronic final states and on rare decays of hadrons madeof heavy flavours, offer a powerful way to set constraints on new physics. Furthermore, heavyquarks hadronize in various charmed and beauty hadrons with a large number of possible decays todifferent final states. This increases the observability of CP violation effects. Therefore, precisionmeasurements of heavy-flavour decays provide us with stringent tests of the Cabibbo-Kobayashi-Maskawa (CKM) theory [1, 2].A session of the workshop was dedicated to heavy-flavour production in heavy-ion collisions.Heavy-flavour production in high-energy collisions of heavy ions and protons is an excellent probeof the quark-gluon plasma (QGP) state of matter. Investigations of extreme conditions of QCDmatter at very high density and temperature open a way to understand the universe in a few mil-lionths of a second after the Big Bang, and to set strong constraints on various model calculationsfor heavy-flavour QGP interactions. New heavy-flavour production measurements in proton anddeuteron heavy-ion collisions were presented by the PHENIX, STAR, and ALICE collaborations.Many future high-energy physics programs at colliders for the next years will be focussed onthe search for any possible signature of physics beyond the SM (BSM). All of the topics presentedin the heavy-flavour working group sessions of the DIS2015 workshop are extremely important inthis respect. Heavy-flavor physics will play a crucial role in achieving this goal. This was reflectedin all experimental and theoretical analyses presented, which triggered a large number of interestingand lively discussions. In what follows, the studies presented in the heavy flavour working groupsessions are briefly summarized in chronological order.2 eavy-flavour Physics Highlights Marco Guzzi
2. Heavy-flavour production in heavy-ion collisions
Heavy flavors are suggested as excellent probes to study the properties of the hot and densenuclear matter created in high-energy heavy ion collisions in the Relativistic Heavy Ion Collider(RHIC) and ALICE experiments. These measurements will be a key to understand evolutionof medium effects from proton-proton ( pp ) to heavy-ion collisions. S. Lim presented measure-ments [3, 4] of the transverse momentum p T of leptons decaying from charmed/beauty hadrons indeuteron + gold ( d + Au ) collisions at the PHENIX experiment, and discussed several model cal-culations. Results in Fig.1(left) show suppression of the heavy-flavour pair production at forwardrapidity. Z. Ye presented recent results [5] on open heavy-flavor production through semi-leptonicdecay channels from the STAR experiment. The results show a strong suppression for the Non-Photonic Electron (NPE) production at √ s NN =
200 GeV in gold-gold ( Au + Au ) collisions. InFig.1(right) Non-photonic electron azimuthal anisotropies are compared to different model calcu-lations at √ s NN =
200 GeV. D. Thomas presented measurements [6] of open heavy-flavour pro-duction cross sections and their dependence on charged particle multiplicity in pp ( √ s = .
76 TeVand √ s = p + Pb ) collisions ( √ s = .
02 TeV) at the ALICE experiment.Differences between two-particle correlation distribution in high (0-20%) and low (60-100%) mul-tiplicity in the ( D h , D f ) space, are shown in Fig.2(left), where a double-ridge structure is observedin heavy-flavour decay electron azimuthal angular correlations in p + Pb collisions. K. Kovarikpresented a theory talk in which theoretical predictions obtained with shower Monte Carlo pro-grams are compared to different theories where fixed-order calculations are extended with next-to-leading logarithms and to predictions using the General Mass Variable Flavour Number Scheme(GM-VFNS). Results [7] are compared to recent measurements of heavy-flavour production in pp collisions at the ALICE experiment [8] in Fig.2(right). These findings are important to under-stand theory uncertainty for the baseline processes before studying the heavy-quark suppression inheavy-ion collisions.
3. B-physics and charm/beauty rare decays
Several presentations focused on the physics of the B-meson and rare decays of charm andbottom-quark decays. B-physics and heavy-flavour rare decays are extremely important as theylead to interplays of the flavour sector and collider physics. Moreover, precise measurementsin the flavour sector set severe constraints on new physics. New measurements [9] of B-hadronproduction with the ATLAS experiment were presented by J. Zalieckas. He showed studies of B + c → J / y D ( ∗ )+ s using √ s = 7 and 8 TeV data collected in 2011 and 2012. The main results areshown in Fig.3(left) where branching ratios seem to be generally well described by perturbativeQCD (pQCD) and are consistent with several other theoretical models such as QCD potential [10],and Light-front quark model (LFQM) [11]. These results are found to be consistent with simi-lar measurements [12] performed at the LHCb experiment. M. Chrzaszcz presented rare charmand bottom decays measurements [14] using pp collision data at the LHCb experiment. In par-ticular, he discussed the angular analysis of the B → K ∗ m + m − decays and results for a relevantangular variable are shown in Fig.3(right). Neglecting the correlations between the observables,the measurements seem to be in agreement with the SM predictions, although the P ′ angular3 eavy-flavour Physics Highlights Marco Guzzi d A R (a) 60-88% -2.0 < y < -1.41.4 < y < 2.0=200 GeV NN sd+Au @ (b) 0-20% mfi EPS09s LO, D mfi EPS09s LO, D (GeV/c) T p0 1 2 3 4 5 6 70.511.522.5 (c) 0-100% brodening, CNM E-loss) T I. Vitev (shadowing, p
Figure 1: Left : Suppression of the heavy-flavour production at forward rapidity in d+Au collisions atPHENIX.
Right : Non-photonic electron azimuthal anisotropies in Au+Au collisions at STAR. (r a d ) jD -1 0 1 2 3 4 hD -1.5-1.0-0.50.00.51.01.5 ) - ) ( r a d jD d hD / d h N ) ( d e ( / N = 5.02 TeV NN sp-Pb, (0-20%) - (60-100%), Multiplicity Classes from V0A(e from c,b)-h correlation < 2.0 GeV/c eT hT ALI−PREL−62026ALI−PREL−62026ALI−PREL−62026 ( pb / . G e V ) T / dp s d ALICEPOWHEGGM-VFNSFONLL = 2.76 TeVs)/2 at - m + + m ( fi HF+X fi pp A L I C E / P O W H E G F O N LL / P O W H E G G M - V F N S / P O W H E G (GeV) T p Figure 2: Left : Two-particle correlation distribution in p+Pb collisions at ALICE.
Right : Transverse-momentum distributions of muons from heavy-flavour (charm and bottom-quark) decay produced in theforward region at the LHC with √ s = 7 TeV and compared to ALICE data. observable exhibits a local tension with respect to the SM prediction at a level of 3.7 s . Theseresults have important implications on the limits on anomalous triple gauge bosons couplings.New theoretical models for B-decays were discussed in M. Ahmady’s presentaion [15]. He dis-cussed results obtained from anti-de Sitter Quantum Chromodynamics (AdS/QCD) and used tocalculate light cone distribution amplitudes for r and K ∗ vector mesons. In Fig.4(left) these distri-bution amplitudes, utilized to calculate the B → K ∗ m + m − differential decay width, are comparedto recent LHCb data. CP asymmetries between same-sign inclusive dilepton samples l + l + and4 eavy-flavour Physics Highlights Marco Guzzi + py J/ fi +c B /BR +s D y J/ fi +c B BR ATLAS + py J/ fi +c B /BR +s D* y J/ fi +c B BR +s D y J/ fi +c B /BR +s D* y J/ fi +c B BR G / –– G ATLAS (Run 1)LHCb (Run 1) modelQCD potentialQCD sum rulesRCQMBSWLFQMpQCDRIQM ] c / [GeV q ’ P -1-0.500.51 preliminaryLHCb SM from DHMV
Figure 3: Left : Comparison of the results of this measurement with those of LHCb and theoretical predic-tions based on a QCD relativistic potential model.
Right : The observable P ′ in bins of q . The shadedboxes show the SM prediction of Ref. [13] [rad] fy J/s f -1.5 -1 -0.5 0 0.5 1 1.5 ] - [ p s s GD constrained to > 0 s GD ATLAS
Preliminary = 7 TeVs -1 L dt = 4.9 fb (cid:242)
68% C.L.90% C.L.95% C.L.Standard Model ) s f |cos( G = 2| s GD Figure 4: Left : The AdS/QCD prediction for B → K ∗ m + m − differential decay width. Center : Measure-ments of CP asymmetry in neutral B mixing, including this measurement, recent LHCb result.
Right :Likelihood contours in f s − DG s plane. The blue and red contours show the 68% and 95% likelihood con-tours, respectively (statistical errors only). The green band is the theoretical prediction of mixing-inducedCP violation. l − l − ( l = e , m ) from semileptonic B decays in ¡ ( S ) → B ¯ B events have been measured [16] atthe BaBar experiment and presented by M. Chrzaszcz. These asymmetries are important probesfor CP and T symmetry violations. Results are shown in Fig.4(center) where the CP asymmetry is A CP = ( − . ± . ( stat . ) ± . ( syst . )) × − and is consistent with the SM expectation. T. Nooneypresented results of new physics searches with B mesons at the ATLAS experiment [17]. In partic-ular, she discussed the parameters of B s → J / yf decay and showed that they are consistent withthe values predicted by the SM. Fig.4(right) shows the main results of this study, where the widthdifference DG s of the two B s and ¯ B s mesons is represented in terms of the CP violating phase f s .Many new physics models can significantly affect f s , therefore this observable is suitable to searchfor BSM phenomena.
4. Charm and beauty quark production and exotic mesons
The charm and beauty-quark production process is going to become extremely important forfuture precision programs at colliders. Differential cross sections for the production of charm and5 eavy-flavour Physics Highlights
Marco Guzzi beauty-quark in QCD jets, or in association with vector bosons, are excellent probes of QCD fac-torization and also have the potential to constrain PDFs of the proton, if such measurements aresufficiently precise. The ATLAS, CMS, Tevatron, and HERA experiments presented several newresults for these observables. P. Gunnellini presented new results for the measurement of four-jetproduction including two b-quark jets at the CMS experiment [18] at √ s = p T of the jet is compared to the SM calculation in different rapidity bins. The SM prediction is foundto be in good agreement with the data. P.T. Mastrianni showed recent measurements beauty-quarkpair production associated with a vector boson at the CMS [19, 20, 21] experiment at √ s = 7 TeV.In particular he discussed the total inclusive cross section for pp → Z ( l ¯ l ) + b ¯ bX process, illustratedin Fig.5(right), and compared the experimental measurements to several theoretical QCD calcula-tions at the NLO accuracy. Data and theory are in very good agreement within the uncertainties.Measurements of open charm production in deep-inelastic electron-proton ( ep ) scattering (DIS) at Figure 5: Left : Differential cross sections unfolded to the stable particle level as a function of the jettransverse momenta at CMS 7 TeV.
Right : Total inclusive cross section for pp → Z ( l ¯ l ) + b ¯ bX at CMS 7TeV. HERA provide important input for stringent tests of the theory of strong interactions. Moreoverthese precise measurements provide a consistent determination of several important physical quan-tities such as the charm contribution to the proton structure functions, the charm-quark mass m c ,and allow us to obtain improved predictions for W and Z -production cross sections at the LHC.Several new results from HERA have been presented in the current workshop. A combination ofdifferential D ( ∗ ) ± cross-section measurements from H1 and ZEUS collaborations at HERA [22]was presented by O. Behnke. Perturbative next-to-leading-order QCD predictions are comparedto the results for the p T spectrum of the D ∗ in Fig.6(left). The predictions describe the data well6 eavy-flavour Physics Highlights Marco Guzzi within their uncertainties, although higher order calculations would be helpful to reduce the theoryuncertainty to a level more comparable with the data precision. Further improvements in the treat-ment of heavy-quark fragmentation would also be desirable. M. Wing presented measurementsof D ( ∗ ) photoproduction at three different centre-of-mass energies from the ZEUS collaborationat HERA [23]. The dependence on the ep centre-of-mass energy was presented for the first time.Variations of the cross section with centre-of-mass energy are sensitive to the gluon PDF in theproton, as different values of Bjorken x are probed. The main results are shown in Fig.6(right)where the normalised D ( ∗ ) visible photoproduction cross sections as a function of the ep centre-of-mass energy are compared to NLO QCD theory predictions. Measurements are in good agreementwith QCD predictions. B.K. Abbott presented for the first time a new measurement of the forward- (GeV)s
240 260 280 300 320 s R ZEUS
D* T D* h | < 1 GeV Q = æ W Æ
136 GeV 152 GeV 192 GeV D* X fi ZEUS epPYTHIANLO QCD
Figure 6: Left : Differential D ( ∗ ) ± -production cross section as a function of p T ( D ) at HERA. The datapoints are the combined cross sections. Right : Normalised D ( ∗ ) visible photoproduction cross sections as afunction of the ep centre-of-mass energy at HERA. backward asymmetry ( A FB ) in the production of B ± mesons in p ¯ p collisions at the D0 experimentduring the Run-II of the Tevatron collider [24, 25]. He showed that D0 measured no significantforward-backward asymmetry. The result for A FB ( B ± ) = − . ± . ( stat ) ± . ( sys ) illustrated in Fig. 7(left), is compatible with zero. Locally, some tensions between data and theMC@NLO [26] theory prediction are found. Nonzero asymmetries would indicate a preferencefor a particular flavor, i.e., b quark or b antiquark, to be produced in the direction of the protonbeam. These measurements provide important constraints on the production mechanisms of heavyquarks at hadron colliders.Searches of exotic states are going on at the LHC. In particular the existence of the X ( ) resonance suggests the presence of its bottomonium counterpart X b . J.M. Izen presented a studyin which searches for X b states with the ATLAS experiment [27] in final states including p + p − ¡ channel, are discussed. The main results are shown in Fig.7(right), in which exclusion limits forthe relative production rate of the X b state are given as a function of its mass.
5. Top-quark physics: production and properties
The top-quark physics sessions of the current workshop were very active and triggered severalinteresting discussions. New results were presented from both experimental collaborations and7 eavy-flavour Physics Highlights
Marco Guzzi (B) h £ h £ h h ( % ) F B A -3-2-1012345 DataMC@NLO -1 (a) DØ, L = 10.4 fb (B) (GeV) T p ( % ) F B A -6-4-20246 DataMC@NLO -1 (b) DØ, L = 10.4 fb Figure 7: Left : Comparison of A FB ( B ± ) and A SMFB ( B ± ) in bins of | h B | and p T ( B ) . Data points and MC bandsinclude statistical uncertainties convoluted with systematic uncertainties. Right : Observed 95% CL upperlimits (solid line) on the relative production rate of a hypothetical X b parent state decaying isotropically to p + p − ¡ , as a function of mass. theorists. J. Wilson presented new results for the measurements of differential forward-backwardasymmetries as a function of rapidity D y = y t − y ¯ t and invariant mass of bottom- and top-quarkpair production at CDF Tevatron [28]. Recent measurements for the M t ¯ t distribution for A FB areillustrated in Fig.8(left) where these are compared to the POWHEG [29] theory prediction. It hasbeen recently found [30] that the NNLO QCD corrections to the top-quark pair production crosssection are large (27% of the NLO) and when these are combined with the EW (25% of the NLO)corrections, produce inclusive A FB ≈ M t ¯ t differential asymmetry togetherwith the CDF [31] and D0 [32] measurements. The agreement between the data and theory hasimproved, and the NNLO theory is less than 1.5 s below the CDF data. -0.4-0.2 0 0.2 0.4 0.6 350 400 450 500 550 600 650 700 750 A FB M tt [GeV]m t =173.3 GeVMSTW2008 pdfNLONNLOCDFD0 Figure 8: Left : The parton-level M t ¯ t distribution for the A FB at CDF [31]. The shaded region represents thetheoretical uncertainty on the slope of the prediction. Right : M t ¯ t distribution for the A FB in pure QCD atNLO (blue) and NNLO (orange) versus CDF [31] and D0 [32] data. eavy-flavour Physics Highlights Marco Guzzi
N. Kidonakis reported about the recent progress in approximate QCD calculations for top-quark pair production using logarithmic threshold expansions of the resummed cross section. Inparticular, he showed approximate cross sections up to NNNLO ( O ( a s ) ) for relevant t ¯ t observablesat the LHC and Tevatron [33]. In Fig.9(left) these higher-order corrections are shown and arecompared to recent LHC measurements. p T (GeV) / s d s / dp T ( G e V - ) aN LOscale variation+ CMS
Normalized top p T distribution at the LHC S =7 TeV
200 300 40010 -4 -3 [TeV] s c r o ss s e c t i on [ pb ]tI n c l u s i v e t ATLAS+CMS PreliminaryTOPLHCWG
May 2015 * Preliminary ) -1 Tevatron combined* 1.96 TeV (L=8.8 fb) -1 ATLAS dilepton 7 TeV (L=4.6 fb) -1 CMS dilepton 7 TeV (L=2.3 fb ) -1 ATLAS l+jets* 7 TeV (L=0.7 fb) -1 CMS l+jets 7 TeV (L=2.3 fb ) -1 ATLAS dilepton 8 TeV (L=20.3 fb) -1 CMS dilepton 8 TeV (L=5.3 fb ) -1 * 8 TeV (L=5.3-20.3 fb m LHC combined e ) -1 ATLAS l+jets 8 TeV (L=20.3 fb) -1 CMS l+jets* 8 TeV (L=2.8 fb
NNLO+NNLL (pp))pNNLO+NNLL (pCzakon, Fiedler, Mitov, PRL 110 (2013) 252004 uncertainties according to PDF4LHC S a ¯ = 172.5 GeV, PDF top m Figure 9: Left : Normalized aN3 LO top-quark pT distributions at the 7 TeV LHC, and comparison withCMS data [34].
Right : Summary of LHC and Tevatron measurements of top-quark pair production.
J.G. Garay, A. Jung, S. Protopopescu, and C. Schwanenberger gave detailed presentationsand overviewes on the current status of measurements for top-quark pair production inclusive anddifferential cross sections at the ATLAS and CMS experiments. C. Schwanenberger summarizedresults of the measurements of t ¯ t + jets, t ¯ t + g , t ¯ t + Z , and t ¯ t + W production at the ATLAS experi-ment [35]. Top-quark properties and decays were also extensively discussed. Preliminary ATLASand CMS combined results for the inclusive t ¯ t cross section measurements at √ s = t ¯ t pair production cross section are shown as a function of the centre-of-mass energyand are compared to the NNLO QCD calculation complemented with NNLL resummation [38].Examples of measurements of top-quark pair production differential cross sections at ATLAS [39]and CMS [40] at √ s = x region, where these are currently poorly determined [41]. Moreover, these measure-ments provide us with the possibility of pinning down the correlations between the cross section,PDFs, a s , and top-quark mass. S. Menke and H. Liu presented measurements of the top-quarkmass m t at the LHC and Tevatron respectively. Very recent m t measurements at ATLAS [42] 7TeV and CMS [43] at 8 TeV are shown in Fig.11, where the CMS summary result of LHC Run-I is m t = . ± . ( stat ) ± . ( sys ) GeV. The preliminary ATLAS summary result of the 7 TeVRun-I is m t = . ± . ( stat ) ± . ( sys ) GeV. The March 2014 Tevatron plus LHC combinedresult is m t = . ± . ( stat ) ± . ( sys ) GeV. The results presented by H. Liu for the m t combined measurements from CDF and D0 experiments at the Tevatron collider [44] are shown inFig.11(right). The Tevatron combination resulted in m t = . ± . ( stat ) ± . ( syst ) GeV.Measurements of the top-quark properties in the production and decays of t ¯ t events at CMS [45] andATLAS [46] were discussed by A. Jung. In particular he discussed measurements of the top-quark9 eavy-flavour Physics Highlights Marco Guzzi
Figure 10: Left : Normalized differential cross-section of highly boosted top quarks as a function of the topquark p T . Right : Normalized differential t ¯ t production cross section in the l +jets channels as a function ofthe top-quark p T pair charge asymmetry, W helicity in top decays, top-quark charge, t ¯ t spin correlation, and searchesfor anomalous couplings. A sample of the main results is shown in Fig.12(left) (ATLAS) and inFig.12(right) (CMS), where they are compared to the SM predictions and are found to be in agree-ment. K. Finelli presented measurements of single-top production cross section at ATLAS [47]and CMS [48]. Inclusive and differential cross sections measured in all channels were discussed.The ATLAS and CMS preliminary combination for the total inclusive cross section for single topproduction is shown in Fig.13(left). Single-top physics is a probe for BSM physics. In fact, sin-gle top-quark production cross sections set stringent limits on the mass of extra charged currentsdecays of W ′ → tb . Two recent studies are shown at ATLAS [49] and CMS [50] in Fig.13(center,right), where exclusion limits for the mass of right-handed W ′ s are given.
6. Heavy flavours in global QCD analyses of proton PDFs
This section is concerned with the impact of heavy flavours in the determination of the struc-ture of the proton in global QCD analyses of world experimental data. Measurements of heavy-flavour cross sections play a crucial role in the most recent PDF global analyses [51, 52, 53, 54, 55,56, 57], and are an essential ingredient of the LHC run-II program [58]. LHC run-II measurementswill set a completely new frontier for PDFs accuracy, as they will be constrained in new kinematicregions. Precise determination of PDFs and reduction of their uncertainties are crucial for a correctestimate and characterization of LHC cross sections and for new physics searches. In the stud-ies presented at this workshop, several very recent heavy-flavour cross section measurements havebeen exploited to constrain PDFs in kinematic regions so far unexplored.T.J. Hou presented a detailed analyses of the predictions for gg → H and t ¯ t cross sections atthe LHC 7, 8 and 13 TeV, as well as their uncertainties from both the PDFs and the strong coupling a s , in the context of the recent CT14 global QCD analysis [51]. In particular, he discussed aconsistency check between the Lagrange multiplier and Hessian method. Some of the main resultsare shown in Fig.14, where the behaviour of the c as a function of the total inclusive NNLO t ¯ t pair10 eavy-flavour Physics Highlights Marco Guzzi ) (GeV/c t M165 170 175 180 18509
CDF March’07 – – – ( Tevatron combination * – – – ( syst) – stat – ( DØ-II lepton+jets – – – ( CDF-II lepton+jets – – – ( CDF-II MET+Jets – – – ( CDF-II alljets * – – – ( DØ-II dilepton – – – ( CDF-II dilepton * – – – ( Mass of the Top Quark (* preliminary)
July 2014 /dof = 10.8/11 (46%) c (Run I and Run II) Figure 11: Left : Summary of the latest ATLAS direct m t measurements. Center : Summary of the eightCMS m t measurements and their combination. Right : CDF and D0 m t measurements and their combination. production cross section (left), and a contour plot (right) of D c ( s t ¯ t , a s ( M Z )) in the ( s t ¯ t , a s ( M Z )) plane at the LHC 13 TeV, are illustrated. This type of test is extremely important to validate thehessian analysis and check the consistency of PDF uncertainties in kinematic regions where thereare no data to set constraints.A. Geiser presented a novel analysis [59] on behalf of the Prosa collaboration [60], in whichrecent LHCb measurements of charm and beauty production cross sections [61, 62], in conjunctionwith HERA data [63], are used in a NLO PDF analysis to directly constrain the gluon PDF down to x ≈ · − . This kinematic range is currently not covered by other experimental data in perturba-tive QCD fits. One of the key differential cross-section measurements for the charmed D0 mesonproduction at the LHCb experiment, is illustrated in Fig.15(left). The main finding of this analysisis illustrated in Fig.15(right), where the gluon PDF is found to be positive and well constrained at x ≈ − .G. Brandt discussed an extension of the HERAPDF2.0 QCD fit [54] in which data of charmand jet-production cross section are used to obtain a simultaneous determination of PDFs and11 eavy-flavour Physics Highlights Marco Guzzi
Figure 12: Left : Comparison of the inclusive A llC and A t ¯ tC measurement values to the theory predictions (SMNLO QCD+EW prediction). Right : The right-handed helicity fraction of the W boson from the top quarkdecay. Figure 13: Left : Summary of ATLAS and CMS measurements of the single-top production cross-sectionsin various channels as a function of the center of mass energy.
Center : Observed and expected 95% CLlimits on the W ′ -boson cross-section times branching ratio prediction, as a function of the mass of the W ′ boson, for right-handed W ′ bosons at ATLAS 8 TeV. Right : Upper limits on the production cross-section ofright-handed W ′ bosons obtained for combination of the electron and muon channels at CMS 8 TeV. a s ( M Z ) . The new PDFs obtained in this simoultaneous fit are called HERA2.0Jets [54]. The result-ing value of the strong coupling constant is a s ( M Z ) = . ± . ( exp ) ± . ( model / param . ) ± . ( hadronisation ) + . − . ( scale ) . This value is in excellent agreement with theworld averge a s ( M Z ) = . c forvarious determinations of a s ( M Z ) . In the (right) panel the HERAPDF2.0Jets PDFs at factoriza-tion scale m f =
10 GeV obtained from a NLO fit with free a s ( M Z ) , are illustrated. A significantreduction of the uncertainty of the gluon PDF is found.
7. Conclusions
Heavy-flavour physics has many implications on the multifaceted aspects of hadronic matter.It is a powerful tool to probe features of QCD in different contexts and it is crucial for searchesof new physics. At this conference, a large number of very interesting new results were presentedconfirming that, even though an impressive amount of important results have already been achieved,12 eavy-flavour Physics Highlights
Marco Guzzi Dc s t – t [pb]CT14 NNLO 13 TeV, a s = 0.118 0 20 40 60 80 100 120 780 800 820 840 860 CT14 NNLO 13 TeV s t – t [ pb ] D c a s
760 780 800 820 840 860 880 900
Figure 14: Left : Dependence of the increase in the constrained CT14 fit on the expected cross section atthe LHC 13 TeV, for a s ( M Z ) = 0.118. Right : Contour plot of
D c ( s t ¯ t , a s ( M Z )) in the ( s t ¯ t , a s ( M Z )) planeat the LHC 13 TeV. ❪❝✥(cid:0)✁✂✄❚♣✵ ✶ ✷ ✸ ✹ ✺ ✻ ✼ ✽✮☎✆❜✝✞✟✠✡✝♠☛ ☞✌✝✴s✴➫➢✍ ✎✏ ✑✒✶✵✑✓✶✵✑✔✶✵✑✕✶✵✶✶✵✔✶✵ ❂ ✖ ✗❡❱✘▲✙✚✛●▼✜❋◆❙ ✐♥tr✳ ✢❤❛r✣●▼✜❋◆❙❋✤◆✦✦✦✧★✩ ✪❛t❛ ✫✬✭ ✯✰✯ ✫✬✱✲ ✾✿✭✫✬✱ ✯✰✯ ❀✬✭✲ ✾✿❁❀✬✭ ✯✰✯ ❀✬✱✲ ✾✿✫❀✬✱ ✯✰✯ ❃✬✭✲ ✾✿❀❃✬✭ ✯✰✯ ❃✬✱✲ ✾✿❃ m f2 = 10 GeV HERA DISHERA DIS + LHCb absHERA DIS + LHCb norm x • g x d g / g -101210 -6 -5 -4 -3 -2 -1 -6 -5 -4 -3 -2 -1 Figure 15: Left : Differential cross-sections for the charmed D0 meson production at the LHCb experiment,compared to NLO theoretical predictions.
Right : Gluon PDF uncertainty as obtained from the QCD fit. a lot of work is ahead to explore key features of QCD and electroweak theory which are crucial toface the challenges of LHC run-II.
8. Acknowledgments
This work is supported in part by the Lancaster-Manchester-Sheffield Consortium for Funda-mental Physics under STFC grant ST/L000520/1.
References [1] N. Cabibbo, Phys. Rev. Lett. 10 (1963) 531.[2] M. Kobayashi and T. Maskawa, Prog. Theor. Phys. 49 (1973) 652.[3] PHENIX, A. Adare et al., Phys. Rev. Lett. 112 (2014) 252301, 1310.1005.[4] PHENIX, A. Adare et al., Phys. Rev. Lett. 114 (2015) 192301, 1404.7461.[5] STAR, L. Adamczyk et al., (2014), 1405.6348.[6] ALICE, E.P.d.O. Filho, Proceedings, 6th International Conference on Hard and ElectromagneticProbes of High-Energy Nuclear Collisions (Hard Probes 2013), 2014, 1404.3983. eavy-flavour Physics Highlights Marco Guzzi
H1 and ZEUS c - c m i n NLO inclusive + charm + jet data, Q inclusive + charm + jet data, Q min = 3.5 GeV inclusive + charm + jet data, Q inclusive + charm + jet data, Q min = 10 GeV inclusive + charm + jet data, Q inclusive + charm + jet data, Q min = 20 GeV c - c m i n NLO inclusive data only, Q inclusive data only, Q min = 3.5 GeV inclusive data only, Q inclusive data only, Q min = 10 GeV inclusive data only, Q inclusive data only, Q min = 20 GeV a s (M Z2 ) c - c m i n NNLO inclusive data only, Q inclusive data only, Q min = 3.5 GeV inclusive data only, Q inclusive data only, Q min = 10 GeV inclusive data only, Q inclusive data only, Q min = 20 GeV -4 -3 -2 -1
10 1 ) Z (M s a HERAPDF2.0Jets NLO, free uncertainties: experimental model hadronisation parameterisation x x f = 10 GeV m v xu v xd 0.05) · xS ( 0.05) · xg ( H1 and ZEUS
Figure 16: Left : D c = c − c vs. a s ( M Z ) for pQCD fits with different Q using data on (a) inclusive,charm and jet production at NLO, (b) inclusive ep scattering only at NLO and (c) inclusive ep scattering onlyat NNLO. Right : The parton distribution functions xu v , xdv , xS = x ( U + D ) and xg of HERAPDF2.0JetsNLO at m f =