Heavy quarkonia perspectives with heavy-ions in ALICE

E. VercellinUniversità and INFN Torino – Italy

For the ALICE collaboration

ALICE Set-up

HMPID

Muon Arm

TRD

PHOS

PMDITS

TOF

TPC

Size: 16 x 26 metersWeight: 10,000 tons

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/: 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)

geom (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

• Quarkonia:– X-sect from Color Evaporation

Model– Pt distribution extrapolated

from CDF data– Feed-down from higher– resonances included– J/ 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) /k : Hijing

For more details see PPR Vol. II – J. Phys. G. Nucl. Part. Phys. 32 (2006)

Quarkonia to dielectrons: Pb-PbDielectron 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 Pb-Pb data taking

Zoom in the J/ region

Zoom in the region

Quarkonia to dielectrons: p-p

Quarkonia to dimuons: Pb-Pb

Statistics for 0.5 nb-1

-J/: excellent (670.000)- ’: marginal - Y: ok (7000)- Y’: low (2000)- Y’’: very low (1000)

Normalization on open bB -> J/ + X

Quarkonia +-: suppression studies in Pb-Pb

Statistical errors corresponding to one month run.Hp : “perfect” subtraction of comb. background Hp. Nucl. Absorpt. cross sect. = 0 (hint from RHIC)

Shadowing + two QGP suppression scenarii: low vs. high diss. temperature

Centrality dependence of J/ and yields normalized to open beauty

Quarkonia +-: suppression studies in Pb-Pb Centrality dependence of ’ / J/ and ’/ ratiosSame working hypothesis as previous slide

J/, Y, Y’: Excellent sensitivity to different suppression scenariosY’’: Needs 2-3 years of high luminosity’:Will be very difficult

Quarkonia to dimuons: pp coll. at 14 TeV Statistics expected in a pp run of 107s at L=31030 cm-2s-1

2.8 106 J/ 2.7 104

Invariant mass resolution at the J/ peak: ~ 70 MeV/c2

Invariant mass resolution at the peak: ~ 100 MeV/c2

Quarkonia to dimuons in pp collisions at 14 TeV: study of pt and y distributions

pt distribution: test of prod.

mechanisms (see Tevatron)

J/ rapidity distribution: sensitivity to gluon distributions at low x ?

(statistics for one pp run : 107s at L=31030 cm-2s-1)

Quarkonia polarization is reconstructed from the angular distribution of the decay products (J/ +- ) in the quarkonia rest frame

θcos α1cosθ ddσ 2

Measurement of quarkonia polarization in pp collisions

y

z

x

H+

pproj ptarg

J/ -

=+1

=-1

Transverse polarization

Longitudinal polarization

With the foreseen pp statistics the measurement of J/ polarization isfeasible in ALICE, also as a function of pT

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