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Quarkonium production in p-p and A-A collisions: ALICE status report

7. Quarkonium production in p-p and A-A collisions: ALICE status report. E. Scomparin (INFN-Torino, Italy) for the ALICE Collaboration. Fermilab, May 18-21, 2010. Introduction. ALICE (A Large Heavy-Ion Collision Experiment):. the dedicated heavy-ion experiment at the LHC.

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Quarkonium production in p-p and A-A collisions: ALICE status report

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  1. 7 Quarkonium production in p-p and A-A collisions: ALICE status report E. Scomparin (INFN-Torino, Italy) for the ALICE Collaboration Fermilab, May 18-21, 2010

  2. Introduction • ALICE (A Large Heavy-Ion Collision Experiment): the dedicated heavy-ion experiment at the LHC • Main focus on Pb-Pb collisions  QGP studies • up to the nominal LHC luminosity, 51026 cm-2s-1 • p-p collisions are a crucial aspect of the physics program • Reference for heavy-ion collision studies • Genuine p-p physics • Maximum luminosity limited to ~3 1030 cm-2s-1 • due to pile-up in TPC • Faster detectors (e.g. muon spectrometer) • may stand a higher luminosity Running conditions appropriate for quarkonium studies (both charmonium and bottomonium)

  3. The ALICE experiment Still to be completed PHOS: 3/5 EMCAL: 4/12 TRD: 7/18 ZDC Quarkonium production can be studied at both central and forward y

  4. Quarkonium measurement in ALICE (1) • Quarkonia can be measured at BOTH central (|y|<0.9) • and forward (2.5<y<4) rapidity • Central barrel (e+e- decay mode) • Tracking+PID in ITS+TPC+TRD TRD • e- reconstruction efficiency • 80-90% for pT>0.5 GeV/c •  mis-identification •  ~ 1%

  5. Quarkonium measurement in ALICE (2) • TPC substantially helps in hadron rejection, at small momenta 85 m3 - NeC2O2N2 gas mixture 557,568 readout channels Maximum drift time = 92 ms Many (>90) 3D points (+dE/dx) per track • Overall TPC+TRD e- reconstruction efficiency ~75%

  6. Quarkonium measurement in ALICE (3) Muon spectrometer • Cathode Pad Chambers for tracking (1.08106 channels) • Resistive Plate Chambers for trigger (2.1 104 channels) Front absorber (10 I) Muon filter (7.2 I) for muon selection • Beam shield to protect muon detectors

  7. Quarkonium measurement in ALICE (4) • Trigger logic: • pT cut (with various thresholds >0.5 GeV/c) • Select particles pointing to the interaction region • Distance of closest approach (DCA) to the vertex for tracks • in the muon spectrometer ALICE Performance Work in Progress With trigger requirement No trigger requirement No trigger With trigger Muons Hadrons Total PYTHIA 7 TeV PYTHIA 7 TeV pp 7 TeV DCA(cm) DCA(cm) • Muon trigger very effective in rejecting • Hadronic contribution • Soft (background related) component

  8. J/ acceptances • As an example, consider pp collisions at √s =7 TeV Central rapidity (|y|<0.9) Forward rapidity (2.5<y<4) No trigger cut Trigger cut pT=0.5 GeV/c Trigger cut pT=1 GeV/c

  9. Physics performance, PbPb collisions,central rapidity • Simulations for the 2010 running conditions (√s = 2.76 ATeV) • still in progress. For the nominal LHC conditions:  ~ 80 MeV J/ ~ 30 MeV, J/ physics accessible,  may need trigger • First estimates for the 2010 PbPb run: ~10000 J/, ~70 

  10. Physics performance, PbPb collisions,forward rapidity • Again, detailed simulation at √s = 2.76 ATeV still not ready • At nominal energy and luminosity, for 106 s running time Integrated yields (no medium effects except shadowing) central J/ ~ 70 MeV  ~ 100 MeV Resonance separation is possible • Centrality dependence of J/ and  yields can be studied • Worse situation for (2S)

  11. Enough for QGP physics ? • Many crucial predictions can be settled at the LHC • Hyerarchy of suppression for both charmonia and bottomonia ? • Observation of  melting? • Charmonia enhancement due to thermal production • at the phase boundary ? (CC = 10RHIC, Volume = 3RHIC) (3S) b(2P) (2S) b(1P) (1S)  Andronic et al., Phys. Lett. B652(2007) 259 Digal et al., Phys.Rev. D64(2001) 094015

  12. pp collisions, central rapidity • ALICE is luminosity limited, due mainly to pile-up in the TPC, • to 3 1030 cm-2s-1 240 kHz interaction rate • Data taking rate limited to ~1kHz (a few 100 Hz in Pb-Pb) • Need electron trigger (level 1,2) to provide a reduction • factor ~200 (under study) • pp first run at 7 TeV • (109 MB event sample) • No trigger  a few 102 J/ • With L1 trigger  a few 105 J/ ! • Statistics would increase by a factor • 7-10 with full TRD installed J/ efficiency with single-e L1 trigger

  13. pp collisions, forward rapidity • At nominal LHC energy (107 s run, L= 3 1030 cm-2s-1) • Spectrum dominated by correlated • background (low multiplicity, the • uncorrelated contribution is small) • It will be possible to study J/ pT • differential distribution with • reasonable statistics up to 20 GeV/c • First pp run at 7 TeV • Depending on the maximum luminosity chosen for ALICE, • and assuming, tentatively, LHC=0.12 • L= 3 1029 cm-2s-1 (beginning) 104 J/ month-1 • L= 3 1030 cm-2s-1  105 J/ month-1

  14. Other charmonia resonances: c m=m(e+e- )-m(e+e-) • C  J/+ (pp collisions at midrapidity) • Photon conversion: opposite sign tracks associated to a V0, • with cuts on the angle (<0.1 rad) and mass (<0.15 GeV/c2) • Electron triggering crucial also for this signal • Expected statistics from first run: ~2000 c

  15. Bottomonium production • Forward rapidity, nominal √s and luminosity, 107 s running time • Good statistics allows a detailed • study of differential distributions • and polarization • Measurement feasible also in • the first run at 7 TeV • Central rapidity, triggering is mandatory for a meaningful • statistics

  16. (J/ bck subtr) (J/ + bck)  = 0 Quarkonia polarization, forward y J/ • Bias on the evaluation of the • J/ polarization due to the • background is not very large • (as expected) • with 200K J/, the error on • J/ is < 0.02  • With the available  statistics we • can evaluate the polarization with a • statistical error between 0.05–0.11 • Statistical errors, for the pT • dependence of the polarization, vary • between 0.03 -0.2 ALICE expected statistics in 1 year ~ 3 times  CDF statistics (Run I, 3 yr)

  17. J/ from B hadrons • Feasible in the central barrel, thanks to the very good impact • parameter resolution (r < 60m for pT>1 GeV/c) with results corresponding to 4109 MB events (7/18 TRD) • Forward detection more difficult • 3-muon events • upgrade with Si tracker in front of muon spectrometer

  18. Muon-chamber alignment ongoing ALICE work in progress First quarkonia signals in ALICE Forward rapidity Central rapidity After a few weeks running at 7 TeV, quarkonia signals start to pop out Luminosity now increasing..... ...expect physics results soon!

  19. Conclusions • ALICE: an experiment conceived for heavy-ion running, • but with good pp capabilities • Luminosity limited (TPC) to L~31030 cm-2s-1 , but enough • for most charmonium/bottomonium related signals • Crucial detectors for quarkonia measurement in good shape • from the beginning of the LHC run at 7 TeV • TRD to be completed asap First quarkonium signals (J/) have been observed: physics results expected soon

  20. Starts from ||<0.9 (not y) 10 TeV differential distributions (CDF extrapolation)

  21. ITS ACORDE EMCAL HMPID TRD TPC MUON ARM PMD, V0 ZDC TOF PHOS

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