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

Introduction ALICE (A Large Heavy-Ion Collision Experiment): the dedicated heavy-ion experiment at the LHC Main focus on Pb-Pb collisions  QGP studies at 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 a few 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)

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

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 Resolution ? TRD e- reconstruction efficiency 80-90% for pT>0.5 GeV/c  mis-identification  ~ 1%

Quarkonium measurement in ALICE (2) TPC substantially helps in hadron rejection, at small momenta SPD first layer requirement would give another factor 0.85 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 single e reconstruction efficiency ~75% (further requirement of a hit in the internal SPD layer, to improve vertex resolution, gives a 0.85 reduction factor)

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

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 No trigger requirement With trigger requirement Muons Hadrons Total PYTHIA 7 TeV PYTHIA 7 TeV No trigger With trigger DCA(cm) DCA(cm) Muon tracking-trigger matching very effective in rejecting Hadronic contribution Soft (background related) component

J/ acceptances As an example, consider pp collisions at √s =7 TeV Central rapidity (|y|<0.8) Forward rapidity (2.5<y<4) Internal SPD layer required PID electron efficiency to be folded on top No trigger cut Trigger cut pT=0.5 GeV/c Trigger cut pT=1 GeV/c

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

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) J/ (2S) (1S) (2S) (3S) 7105 2104 7103 2103 1103 central J/ ~ 70 MeV  ~ 100 MeV Resonance separation is possible Centrality dependence of J/ and  yields can be studied Worse situation for (2S)

Enough for QGP physics ? Many crucial predictions can be settled at the LHC Hierarchy of suppression for both charmonia and bottomonia ? Observation of  melting? Charmonia enhancement due to statistical 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

pp collisions, central rapidity For L=3 1030 cm-2s-1  240 kHz interaction rate Data taking rate limited (TPC) to ~1kHz (a few 100 Hz in Pb-Pb) Need electron trigger (Level 1,2) to provide a reduction factor ~200, however a TRD L1 trigger (under study) can inspect events at a maximum rate ~ 100 kHz pp first run at 7 TeV (109 MB event sample) No trigger  a few 102 J/ Substantial increase with L1 trigger Statistics would increase by a factor 7-10 with full TRD installed J/ efficiency with single-e L1 trigger

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) S [x103] S/B S/√(S+B) J/ 2800 12 1600 ’ 75 0.6 170 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

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: ~200-300 c

Bottomonium production Forward rapidity, nominal √s and luminosity, 107 s running time S [x103] S/B S/√(S+B)  27 10.4 157 ’ 6.8 3.4 73 ’’ 4.2 2.4 55 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

Quarkonia polarization, forward y J/ (J/ bck subtr) (J/ + bck) 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  = 0 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)

results corresponding to 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 and 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 (?)

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

Conclusions ALICE: an experiment conceived for heavy-ion running, but with good pp capabilities Luminosity limited (TPC) to a few 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

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

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