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J/ψ Measurements with the ALICE Experiment at the LHC

J/ψ Measurements with the ALICE Experiment at the LHC. Julian Book 28th Winter Workshop on Nuclear Dynamics. Outline. Physics Motivation The ALICE Experiment Prompt and Non-Prompt J/ψ Measurements in pp Collisions Nuclear Modification in Heavy-Ion Collisions Summary Outlook.

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J/ψ Measurements with the ALICE Experiment at the LHC

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  1. J/ψ Measurements with the ALICE Experiment at the LHC • Julian Book • 28th Winter Workshop on Nuclear Dynamics

  2. Outline • Physics Motivation • The ALICE Experiment • Prompt and Non-Prompt J/ψ Measurements in pp Collisions • Nuclear Modification in Heavy-Ion Collisions • Summary • Outlook

  3. Motivation: J/ψ in Heavy-Ion Collisions • Quark-Gluon Plasma (QGP): Deconfined state of strongly interacting matter • J/ψ suppression proposed as a signature [T.Matsui, H.Satz, Phys.Lett. B178(4),416-422 (1986)] • QGP induced effects in AA • Melting due to Debye-screening • (Re)combination of uncorrelated ccbar • Thermal production (only at LHC) • Suppression at SPS and RHIC (80,40%) • Larger suppression at large rapidity NA60, Nucl.Phys. A 830:345c-352c (2009) PHENIX, arXiv:1103.6269 (2011)

  4. Motivation: J/ψ in pp Collisions • Provide information on production models (CSM, NRQCD, CEM) • Elementary production not yet well understood • Crucial reference for nuclear modification in Pb-Pb • Multi-Parton Interations on soft, soft-hard, hard scale? • Study pp collisions in different event classes, e.g. impact parameter 1 multiplicity asbdbashbdasdasdsadasddasfsdfJ.P.Lansberg: Phys.Lett. B 695 (2011) 149 M.Butenschoen, B.A. Kniehl arXiv:1201.3862 (2012) C. Marquet, MPI Workshop, Perugia (2008)

  5. Inclusive and Prompt J/ψ Measurements in ALICE Down to pT = 0 midrapidity |y|<0.9: ITS + TPC forward rapidity 2.5 < y < 4.0: ITS + MUON

  6. Proton-Proton Collisions at √s = 2.76 and 7 TeV

  7. Invariant Mass Distributions Midrapidity |y|<0.9 Forward rapidity 2.5<y<4.0 ALICE Coll., Phys.Lett. B704(2011)442

  8. Inclusive Cross Sections: pT and y Dependence • Measurements down to pT = 0 • Good agreementwithLHCbresults • Complementary to CMS and ATLAS • Crucialreferenceforthemeasurement of nucleareffects ALICE Coll., Phys.Lett. B704(2011)442, arXiv:1203.3641

  9. Model Comparison: pT and y Dependence • NRQCD at NLO satisfactorilydescribesbothenergies at forward • rapidity • CS-Model compatiblewithdatawithinvery large uncertainties ALICE Coll., Phys.Lett. B704(2011)442, arXiv:1203.3641

  10. Contribution from B-hadrons 1.3 < pT < 7 GeV/c ; |y|<0.9 • fraction from B-hadron decays: • 0.137 +- 0.054(stat) + 0.025 -0.018 (syst)  +0.022 -0.027 (syst polar.) • Strongly pT dependent, rises up to 70% at 40 GeV/c   ATLAS: Nucl.Phys. B850 (2011) 387, LHCb: Eur.Phys.J. C71 (2011) 1645, CMS: Phys.J. C71, (2011) 1575

  11. Inclusive Cross Sections: Energy Dependence at midrapidity • Strong energy dependence at midrapidity • Almost 2x(10x) larger cross sections than at Tevatron (RHIC) compared to 7 TeV results ALICE Coll., arXiv:1203.3641 (2012)

  12. First J/ψ Polarization Measurement at LHC • Consistentwith no polarization • Signfor longitudinal polarization at lowpT in thehelicityframe • NRQCD at NLO provides a trendlike in thedata ALICE Coll., Phys.Rev.Lett. 108, 082001 (2012) M.Butenschoen, B.A. Kniehl arXiv:1201.3862 (2012)

  13. Charged Particle Multiplicity at Midrapidity • Relative charged particle multiplicity • Up to 5 times the mean multiplicity • Similar significance of J/ψ signal in all intervals ALICE Coll., Eur.Phys.J. C 68: 345–354 (2010) ALICE Coll., arXiv:1202.2816 (2012)(submitted to P.L. B)

  14. Invariant Mass Distributions Midrapidity |y|<0.9 Forward rapidity 2.5<y<4.0 low high multiplicity ALICE Coll., arXiv:1202.2816 (2012)(submitted to P.L. B)

  15. J/ψ Yield as a Function of Charged Particle Multiplicity • Approximately linear increase with midrapidity dNch/dη • Similar behaviour in different rapidity regions • Enhancement relative to min. bias. yield up to 5(8) at forward (mid-) rapidity • PYTHIA shows an opposite trend ALICE Coll., arXiv:1202.2816 (2012)(submitted to P.L. B)

  16. Pb-Pb Collisions at √sNN = 2.76 TeV

  17. Signal in Pb-Pb Collisions at √sNN = 2.76 TeV Forward rapidity 2.5<y<4.0 Double exponential (Background) + Crystal Ball function (Signals)

  18. Nuclear Modification Factor Centrality dependence • RAA = 0.545 ± 0.032(stat.) • ± 0.084(syst.) • Less supression at forward rapidity compared to lower √sNN • No significant centrality dependence ALICE Coll., arXiv:1202.1383 (2012)(submitted to P.R.L.)

  19. Nuclear Modification Factor Centrality dependence • RAA = 0.545 ± 0.032(stat.) • ± 0.084(syst.) • Less supression at forward rapidity compared to lower √sNN • No significant centrality dependence • Stat. Hadronization and transport models can describe the trend in data X.Zhao, R.Rapp, Nucl.Phys. A859 114-125 (2011) Y.P.Liuet.al., Phys.Lett. B678 72-76 (2009) ALICE Coll., arXiv:1202.1383 (2012)(submitted to P.R.L.)

  20. Nuclear Modification Factor Rapidity dependence • Current parametrizations for shadowing affect the RAA by max. 30% • Need for pA measurements • No explicit rapidity dependence ALICE Coll., arXiv:1202.1383 (2012)(submitted to P.R.L.)

  21. Summary • Inclusive J/ψ measurements in pp collisions at √s = 2.76 and 7 TeV • results covering a large rapidity area and pT = 0 • Polarization in pp collisions at √s = 7 TeV at LHC • in the forward region consistent with no polarization • Fraction of non-prompt J/ψ production at √s = 7 TeV • ~14% of J/ψ yield originates from B-hadron decays, strongly pT dependent • Multiplicity dependence of relative J/ψ yields in pp collisions • linear increase of J/ψ yield with midrapidity dNch/dη • Inclusive nuclear modification factor in Pb-Pb collisions at √s = 2.76 TeV • no significant centrality and rapidity dependence • less supression than at RHIC • less supression at low pT

  22. Outlook • Pb-Pb collisions • RAA in central rapidity • Elliptic flow v2 • pA analysis (data end of 2012) • pp collisions • TRD trigger on electrons Midrapidity |y|<0.9

  23. BACKUP

  24. Model Comparison Direct J/ψ from Hard Processes in PYTHIA String Interaction Model • PYTHIA showsanti-correlationforhardproduced J/ψ • decreasenotyetunderstood • Enhancements up to ~4.5 explainablebycollisiongeometry • „High densitymedium“ at midrapidity ? ALICE Coll., arXiv:1202.2816 (2012)(submitted to P.L. B) E.G.Ferreiro, C.Pajares, arXiv:1203.5936 (2012) M.Strikmanet.al., Phys.Rev.Lett. 101, 202003 (2008)

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