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

Heavy quarkonia perspectives
with heavy-ions in ALICE
E. Vercellin
Università and INFN Torino – Italy
For the ALICE collaboration
Size: 16 x 26 meters
Weight: 10,000 tons
TOF TRD
HMPID
ITS
PMD
Muon Arm
PHOS
TPC
ALICE Set-up
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
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
Quarkonia acceptance – dielectron channel
Dielectron trigger: pt
cut of 3 GeV/c on
individual electrons.
Not always needed
(e.g. Pb-Pb central).
Running conditions at Point 2
Collision system
√sNN(TeV)
L0 (cm-2s-1)
Run time
(s/year)
sgeom
(b)
pp
14.0
1031 *
107
0.07
PbPb
5.5
1027
106 **
7.7
pPb
8.8
1029
106
1.9
ArAr
6.3
1029
106
2.7
*Lmax = 1034
** Lint (ALICE) ~ 0.5 nb-1/year
+ other ions (Sn, Kr, O) & energies (e.g.: pp @ 5.5 TeV)
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
Quarkonia to dielectrons: Pb-Pb
Dielectron invariant mass spectrum in central collisions after
one “ALICE-year” of Pb-Pb data taking
Quarkonia to dielectrons: Pb-Pb
Dielectron invariant mass
spectrum in top 10%
central collisions after
one “ALICE-year” of PbPb data taking
Zoom in the J/Y region
Zoom in the  region
Quarkonia to dielectrons: p-p
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)
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)
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
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
Invariant mass resolution at the
J/Y peak: ~ 70 MeV/c2
2.7 104 
Invariant mass resolution at the
 peak: ~ 100 MeV/c2
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: test of prod.
mechanisms (see Tevatron)
J/y rapidity distribution:
sensitivity to gluon
distributions at low x ?
Measurement of quarkonia polarization in pp collisions
Quarkonia polarization is reconstructed from
the angular distribution of the decay products
(J/y  m+m- ) in the quarkonia rest frame
dσ
 1  α cos 2θ
d cosθ
+
m
x
pproj
J/y
y
H
m-
ptarg
=+1
Transverse polarization
=-1
Longitudinal polarization
With the foreseen pp statistics the
measurement of J/y polarization is
feasible in ALICE, also as a function of pT
z
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