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Heavy quarkonia perspectives with heavy-ions in ALICE

Heavy quarkonia perspectives with heavy-ions in ALICE. E. Vercellin Universit à and INFN Torino – Italy For the ALICE collaboration. ALICE Set-up. Size : 16 x 26 meters Weight : 10,000 tons. TOF. TRD. HMPID. ITS. PMD. Muon Arm. PHOS. TPC. Quarkonia detection in ALICE.

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Heavy quarkonia perspectives with heavy-ions in ALICE

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  1. Heavy quarkonia perspectives with heavy-ions in ALICE E. Vercellin Università and INFN Torino – Italy For the ALICE collaboration

  2. ALICE Set-up Size: 16 x 26 meters Weight: 10,000 tons TOF TRD HMPID ITS PMD Muon Arm PHOS TPC

  3. Quarkonia detection in ALICE • Performed both in the • dielectron channel (central barrel, key-detector: TRD) • dimuon channel ( forward rapidity region, Muon Spectrometer) • Complementary features and performance

  4. Quarkonia Acceptance – dimuon channel • J/Y: pt,cut= 1 GeV/c • Dimuon trigger: pt cut on individual muons to reject combinatorial background • : : pt,cut= 2 GeV/c

  5. Quarkonia acceptance – dielectron channel Dielectron trigger: pt cut of 3 GeV/c on individual electrons. Not always needed (e.g. Pb-Pb central).

  6. Running conditions at Point 2 *Lmax = 1034 ** Lint (ALICE) ~ 0.5 nb-1/year + other ions (Sn, Kr, O) & energies (e.g.: pp @ 5.5 TeV)

  7. Simulation inputs For more details see PPR Vol. II – J. Phys. G. Nucl. Part. Phys. 32 (2006) • Quarkonia: • X-sect from Color Evaporation Model • Pt distribution extrapolated from CDF data • Feed-down from higher • resonances included • J/y from B decay included • Shadowing (EKS) • Open heavy flavors • X-sect and kinematic distributions from NLO pQCD (NMR) • PYTHIA tuned to NLO for event generation • Shadowing (EKS) • p/k : Hijing

  8. Quarkonia to dielectrons: Pb-Pb Dielectron invariant mass spectrum in central collisions after one “ALICE-year” of Pb-Pb data taking

  9. Quarkonia to dielectrons: Pb-Pb Dielectron invariant mass spectrum in top 10% central collisions after one “ALICE-year” of Pb-Pb data taking Zoom in the J/Y region Zoom in the  region

  10. Quarkonia to dielectrons: p-p

  11. Quarkonia to dimuons: Pb-Pb B -> J/Y + X Normalization on open b Statistics for 0.5 nb-1 • J/Y: excellent (670.000) • Y’: marginal • Y: ok (7000) • Y’: low (2000) • Y’’: very low (1000)

  12. Quarkonia m+m-: suppression studies in Pb-Pb Centrality dependence of J/Y and  yields normalized to open beauty Shadowing + two QGP suppression scenarii: low vs. high diss. temperature Statistical errors corresponding to one month run. Hp : “perfect” subtraction of comb. background Hp. Nucl. Absorpt. cross sect. = 0 (hint from RHIC)

  13. Quarkonia m+m-: suppression studies in Pb-Pb Centrality dependence of y’ / J/y and ’/  ratios Same working hypothesis as previous slide J/Y, Y, Y’: Excellent sensitivity to different suppression scenarios Y’’: Needs 2-3 years of high luminosity Y’:Will be very difficult

  14. Quarkonia to dimuons: pp coll. at 14 TeV Statistics expected in a pp run of 107s at L=31030 cm-2s-1 2.8 106 J/y 2.7104  Invariant mass resolution at the J/Y peak: ~ 70 MeV/c2 Invariant mass resolution at the  peak: ~ 100 MeV/c2

  15. Quarkonia to dimuons in pp collisions at 14 TeV: study of pt and y distributions (statistics for one pp run : 107s at L=31030 cm-2s-1)  pt distribution: testof prod. mechanisms (see Tevatron) J/y rapidity distribution: sensitivity to gluon distributions at low x ?

  16. H z + x J/ - pproj ptarg y =+1 Transverse polarization =-1 Longitudinal polarization Measurement of quarkonia polarization in pp collisions Quarkonia polarization is reconstructed from the angular distribution of the decay products (J/  +- ) in the quarkonia rest frame With the foreseen pp statistics the measurement of J/ polarization is feasible in ALICE, also as a function of pT

  17. Conclusions • Quarkonia production studied in Alice both in the dielectron and dimuon channels • The two methods are complementary under different points of view. • Quarkonia detected over a wide rapidity range from -4 till +0.9 • Thanks to ALICE characteristics, quarkonia will be studied together with all known observables for heavy ion collisions • Measurements in p-p collisions are a relevant part of the ALICE program

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