Heavy Flavours in ALICE

Transcription

1 Heavy Flavours in ALICE Yvonne Pachmayer, University of Heidelberg for the ALICE Collaboration Motivation Cold nuclear matter effects Results from p-pb collisions Open heavy flavour J/ψ, ψ(2s), ϒ(1S) Comparison with models and Pb-Pb results Conclusion

2 Physics Motivation Heavy Flavour in Pb-Pb Collisions Cold nuclear matter effects + hot nuclear matter effects (related to the Quark-Gluon Plasma) D meson RPbPb Elementary collision No nuclear matter effects Heavy-flavour quarks (c, b) Originate from initial scattering processes Sensitive to the full history of the collision Excellent probes to study the de-confined medium produced in Pb-Pb collisions R PbPb ( p T )= 1 T PbPb dn PbPb /dpt d σ pp /dpt 2

3 Physics Motivation Heavy Flavour in Pb-Pb Collisions Cold nuclear matter effects + hot nuclear matter effects (related to the Quark-Gluon Plasma) Elementary collision No nuclear matter effects c J/ψ RPbPb c C o lo r S c r e e n in g J/ψ Meson (cc) Original idea (1986): J/ψ suppression via colour screening discussed as probe of de-confinement Quark-Gluon Plasma screens all charmonia, but charmonium production takes place at the phase boundary ALICE: arxiv: PHENIX: Phys. Rev. Lett. 98 (2007) ; Phys.Rev. C 84 (2011) ; Phys. Rev. C (2005) Matsui, Satz PLB 178 (1986) Braun-Munzinger, Stachel PLB 490 (2000) Thews et al. PRC 62 (2000) 3

4 Physics Motivation Heavy Flavour in p-pb Collisions Cold nuclear matter effects + hot nuclear matter effects (related to the Quark-Gluon Plasma) Elementary collision No nuclear matter effects Cold nuclear matter effects without Quark-Gluon Plasma Control experiment for Pb-Pb measurements Cold nuclear matter effects Gluon shadowing or saturation Initial state energy loss Energy loss of incoming parton Coherent energy loss kt broadening of initial partons Eskola et al., JHEP 0904 (2009) 65 Kharzeev et al., arxiv: Dominguez et al. ArXiv: Vogt PRC 81 (2010) Arleo arxiv: Lourenco et al., JHEP 0902 (2009) 14 4

5 A Large Ion Collider Experiment Muon Spectrometer Forward Muon Arm Acceptance in p-pb/pb-p: Forward: 2.03 < ycms < 3.53 μ-id via tracks matched with trigger system Iron Wall 7 λi Backward: < ycms < pt > 0 GeV/c Trigger Chambers p/pb μ Pb/p Front Absorber 10 λi μ Tracking Chambers Semi-muonic decays: D, B, Λc, μ + anything Charmonium and Bottomonium: J/ψ, ψ(2s), Y(1S) μ+ + μ 5

6 A Large Ion Collider Experiment Central Barrel Central Barrel: -0.9 η 0.9 pt > 0 GeV/c ITS Track impact parameter and PID e e K π TPC TRD TOF Semi-electronic decays: D, B, Λc, e + anything Hadronic decays: D Kπ + s + *+ D J/ψ - + D K Kπ D+ K-π+π+ D*+ D0π+ Charmonium: J/ψ e+ + e 6

7 Electrons from Semi-electronic c/b Decays Analysis strategy Electron Identification with TOF+TPC (more suited for low pt) or EMCal+TPC (more suited for high pt) Subtraction of the background sources via data-tuned MC cocktail or invariant mass analysis dn ppb /dp T 1 R ( p )= ppb T RpPb consistent with unity T ppb d σ pp /dpt within uncertainties RpPb = 1 no nuclear effects 7

8 Electrons from Semi-electronic c/b Decays Analysis strategy Electron Identification with TOF+TPC (more suited for low pt) or EMCal+TPC (more suited for high pt) Subtraction of the background sources via data-tuned MC cocktail or invariant mass analysis dn ppb /dp T 1 R ( p )= Prediction including initial state effects ppb T T ppb d σ pp /dpt agrees with data within uncertainties RpPb = 1 no nuclear effects 8

9 D Meson RpPb Compatible results for D0, D+, D*+ and D+S All results consistent with unity Comparison with models Models including initial state effects describe data (Mangano et al., Nucl. Phys. B 373 (1992) 295. Eskola et al., JHEP 0904 (2009) 065) pqcd calculation for heavy-flavour production with EPS09 parametrizations of nuclear PDF CGC predictions (Fujii-Watanabe, arxiv: ) 9

10 D meson: Comparison RpPb(pT) and RPbPb(pT) RPbPb: suppression up to a factor of 5 at pt ~10 GeV/c for 0-7.5% most central collisions RpPb: results consistent with unity Suppression observed in Pb-Pb is a final state effect charm quark in-medium energy loss 10

11 c c C o lo r S c r e e n in g Quarkonia Kluberg and Satz, arxiv: Matsui, Satz PLB 178 (1986) Karsch, Satz Z. Phys. C 51 (1991) 209 Braun-Munzinger, Stachel PLB 490 (2000) Thews et al. PRC 62 (2000) Start of Collision Mocsy, Eur. Phys. J.C61, 2009 Development of QGP Hadronisation Braun-Munzinger and Stachel, arxiv:

12 J/ψ RpPb vs rapidity Forward and backward: ALICE: arxiv: Significant suppression at mid- and forward rapidity Backward rapidity result consistent with no suppression Pb p p large x-range Pb small x-range Systematic uncertainties: coloured boxes: uncorrelated shaded areas: (partially) correlated grey box at unity: fully correlated 12

13 J/ψ RpPb vs rapidity Forward and backward: ALICE, arxiv: Significant suppression at mid- and forward rapidity Backward rapidity result consistent with no suppression Models of CNM effects Shadowing: Pb backward rapidity datap well reproduced, p strong shadowing favoured at forwardpb Shadowing model CEM + EPS09 NLO Coherent energy loss (Arleo et al., arxiv: ) with pp data parametrization Gluon saturation (Fuji et al., arxiv: ): Color Glass Condensate framework with CEM LO with saturation scale Q2s,A(x=0.01) = GeV/c2 (Vogt, arxiv: ) rapidity Coherent energy loss: Systematic uncertainties: y-dependence well reproduced coloured boxes: uncorrelated shaded CGC areas: calculations: (partially) correlated grey box at unity: fully correlated underestimate the data 13

14 J/ψ RpPb vs pt Backward rapidity Pb p Mid-rapidity p Pb Forward rapidity p Pb Backward rapidity: RpPb shows small pt dependence close to unity Mid-rapidity: RpPb tends to increase with pt, more precision needed Forward rapidity: RpPb increases with pt, consistent with unity for pt > 5 GeV/c At forward rapidity data tends to favour strong shadowing CGC calculations underestimate data Coherent energy loss model overestimates suppression at forward rapidity for pt < 2 GeV/c Vogt, arxiv: , Arleo et al., arxiv: , Fuji et al., arxiv:

15 J/ψ: Comparison RpPb(pT) and RPbPb(pT) Backward rapidity & Forward rapidity Mid-rapidity Different pt dependencies in Pb-Pb and p-pb/pb-p Small CNM effect for pt > 4 GeV/c 15

16 J/ψ: Comparison RpPb(pT) and RPbPb(pT) Backward rapidity & Forward rapidity Mid-rapidity Assuming 2 1 kinematics + factorization of nuclear effect (only npdf as nucl. effects in pa) One among several possible implications of RpPb on RPbPb interpretation Small effects from extrapolated shadowing at pt > 7 (4) GeV/c at mid (forward) rapidity At low pt in Pb-Pb collisions the J/ψ yield is enhanced (or equal to) compared with the expectation from CNM effects 16

17 ψ(2s) RpPb vs rapidity ψ(2s) R ψ(2s) ppb =R J/ψ ppb σ ppb J/ψ σ pp J /ψ σ ppb σ ψ(2s) pp Strong decrease of ψ(2s)/j/ψ from pp to p-pb Not described by initial state CNM effect and coherent energy loss Similar result as PHENIX experiment at snn = 0.2 TeV (arxiv: ) 17

18 ϒ(1S) RpPb vs rapidity Similar RpPb of J/ψ and ϒ EPS09 shadowing in fair agreement within uncertainties 18

19 Conclusion Open heavy-flavour results Good agreement with pqcd calculations including shadowing predictions p-pb results confirm that the suppression in central Pb-Pb collisions is a final state effect charm quark in-medium energy loss J/ψ measurements Support strong shadowing at forward rapidity and/or the coherent energy loss model J/ψ suppression observed in Pb-Pb collisions cannot be ascribed to cold nuclear matter effects alone ψ(2s) suppressed relatively to J/ψ by up to 45% at backward rapidity Final state effect? ϒ(1S) measurements show a similar suppression as the ones from J/ψ but large uncertainties (pp interpolation, limited statistics) More measurements to come, stay tuned! 19

20 Back-Up 20

21 Electrons from Semi-electronic c/b Decays Analysis strategy Electron Identification with TOF+TPC (more suited for low pt) or EMCal+TPC (more suited for high pt) Subtraction of the background sources via data-tuned MC cocktail or invariant mass analysis dn ppb /dp T 1 R ( p )= ppb T Similar result as PHENIX T ppb d σ pp /dpt experiment ( snn = 0.2 TeV) RpPb = 1 no nuclear effects PHENIX: Phys. Rev. Lett. 109 (2012)

22 D Meson RpPb : Comparison with Models Compatible results for D0, D+, D*+ and D+S All results consistent with unity No rapidity dependence observed (within narrow y range) Comparison with models Models including initial state effects describe data (Mangano et al., Nucl. Phys. B 373 (1992) 295. Eskola et al., JHEP 0904 (2009) 065) pqcd calculation for heavy-flavour production with EPS09 parametrizations of nuclear PDF CGC predictions (Fujii-Watanabe, arxiv: ) 22