1. 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

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
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)

3. 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

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
Resolution ?
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
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)

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
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

8. 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

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:
J/ ~ 30 MeV,
 ~ 80 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)
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)

11. 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)

12. 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

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)
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

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: ~ c

15. 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

16. 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
ALICE expected statistics in 1 year ~ 3 times  CDF statistics (Run I, 3 yr)

17. 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 (?)

18. 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!

19. 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

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