Download - Quarkonia with the first LHC data in ALICE

Quarkonia with the first LHC data in ALICE

Mercedes López NoriegaIPNO

25/09/2009

Mercedes López NoriegaRencontre ions lourds – Orsay 25/09/2009 2

Heavy quarks at the LHC• Heavy quarks (c and b) will be

abundantly produced in heavy ion collisions.

• Produced in the initial parton collisions, they can be used to probe deconfinement

• Upsilon (bb) will be produced in an amount of the order of J/ at RHIC

• Some effects might become important:•heavy quarks energy loss in QGP•contributions from secondary quarkonia

SPSPbPbCent

RHICAuAuCent

LHCpp

LHCpPb

LHCPbPb Cent

cc 0.2 10 0.2 1 115

bb - 0.05 0.007 0.03 5

•|η| < 0.9 and -4 <η< -2.5

•Small xBj (10-3 –10-5)

ALICE


Why quarkonia?•Quarkonia: bound states of heavy quarks

–Charmonia (cc): J/, ’, c

–Bottomonia (bb): (1S), (2S), (3S)

•J/ production used as a probe of formed medium

–A deconfined medium J/ suppression due to color screening

(Matsui and Satz, Phys. Lett. B 178 (1986))

–Hard gluons needed for breaking J/ not available in hadron gas

(D. Kharzeev and H. Satz, Phys. Lett. B477 (2000))

–Calculations using lattice QCD: sequential suppression suppression of states is determined by T and their binding energy

• ’, c dissolves at T ~ TC

• J/ dissolves at T ~ 1.5 - 2 TC

(Satz, J.Phys.G32 (2006))


J/ at the LHC

•The suppression has been observed at SPS and RHIC, BUT!–Similar suppression at SPS and RHIC–Stronger suppression at forward than at mid-rapidity

•The results from PbPb collisions at 5.5 TeV will disentangle between the different suppression/regeneration scenarios

–Measuring either an excess on J/ production or a complete melting would imply deconfinement.

–An excess on the production would also indicate thermalization

•But we should take into account that:–bb cross-section will be large:

~ 20% of J/ originate from B decays (B+/- J/ + X+/-) –CNM effects will not be easy to quantify at the beginning (no pA run soon)

F.Karsch et al.: PLB637 75 (2006)

J/ regeneration?

J/ finally melts?

SPS RHIC LHC


ALICE

TRD

TPC

Central |η| < 0.9, in e+e-

• tracking: ITS, TPC, TRD• PID: TRD (e id.), TOF• secondary vertexing: ITS -4.0 < η< -2.5, in μ+μ-

Muon ArmITS

TOF


First pp run at the LHC

Present scenario (July 09)Present scenario (July 09)

900 GeV collisions

First high E collisions

Pilot run

Expected duration ~ shifts ~ weeks ~ months

N bunches @ ALICE 1 1 ( 2) 24 (100 ns spacing)

bunch intensity @ ALICE

5 1010 5 1010 1.5 1010

* m 10 10 3

transverse bunch size µm 280 84 46

luminosity cm-2 s-1 2.9 1027 3.2 1028 2.3 1029

MB rate s-1 150 2400 17 000

interaction rate per bc .01 .21 .06

pile-up probability .006 .11 .03

√spp = 7 TeV

Federico Antinori - Physics Forum - July Federico Antinori - Physics Forum - July 20092009


What ALICE will measure

assuming (just to get a feeling…):assuming (just to get a feeling…):– ““Pilot Run” conditions Pilot Run” conditions

(as in previous slide)(as in previous slide)– 1 kHz TPC rate1 kHz TPC rate– 300 k effective sec / month 300 k effective sec / month

(12% overall efficiency)(12% overall efficiency)

[serious uncertainties in all three…][serious uncertainties in all three…]

Federico Antinori - Physics Forum - July Federico Antinori - Physics Forum - July 20092009

What do we get for each 100 nbWhat do we get for each 100 nb-1-1??

e.g.: e.g.: 40 Hz single muon low p40 Hz single muon low pTT trigger rate trigger rate (based on ALICE-INT-2006-0002)(based on ALICE-INT-2006-0002)

– ~ 13 000 J/~ 13 000 J/ψψ (~150 with p (~150 with pTT > 11 GeV/c) > 11 GeV/c)

– ~ 250 ~ 250 ψψ‘‘– ~ 140 ~ 140 ΥΥ– ~ 35~ 35 Υ Υ‘‘ – ~ 20~ 20 Υ Υ‘‘‘‘


Quarkonia analysis in pp

Baseline for the analysis in PbPb collisions• J/ and Υ production yield and cross section

• J/ polarization• Upsilon family?• CGC

dielectron channel


Quarkonia via μ+μ- in pp

pp at 14 TeV, one year of data taking (integrated luminosity = 30 pb-1)

J/ψ Υ

Mass resolution (MeV/c2) ~70 ~100

Signal/Noise 12.0 10.4

pT range (GeV/c) 0-20 0-8

Counts2.8 106 2.7 104


Secondary J/ψ• χc: contribution ~30%

– χc J/ψ+γ• J/ψ in dielectron channel• γ in γ-convertion

– feasible in pp collisions but requires a trigger strategy which is under study

• B mesons: contribution ~20%– B J/ψ+X

• non-photonic electrons• “B tagging”: simultaneous fit

– Invariant mass distribution– Pseudo proper decay time

– In muon arm • method using 3 muon events is

under study

− tot J/ψ− J/ψ from B− bkg− sum


• Polarization– Angular distribution of μ+ in the

quarkonium rest frame.

•

•

–Upsilon polarization• 1 nominal year for integrated

studies• Several years for differentials

J/ψ polarization

ddcosH

1 cos2H

T 2 L

T 2 L

1 transverse

0 no polarization

1 longitudinal


Here in Orsay...

•J/ψ production yield and cross section in the dimuon channel

– dN/dpT:•yield with proper background estimation •study different fitting procedures

– Corrections •efficiency correction•acceptance correction

– Systematic errors•uncertainty on efficiency and acceptance corrections...

– Estimation J/ψ coming from B• method using 3 muon events is under study

•CGC (more in next slide...)

AccLdt

dpdN

dp

d T

T


J/Ψ RCP: looking for the CGC

x region probed by J/ψ production in p-p 14 TeV in the forward muon spectrometer

Event multiplicity groups:• B: small multiplicity [0-70]• M: medium multiplicity [70-95]• H: high multiplicity [95-150]


PbPb collisions at the LHC

Parameter Units Early Beam Nominal

Energy per nucleon TeV 2.76 2.76

Initial ion-ion Luminosity L0 cm-2 s-1 ~ 5 ×1025 1 ×1027

No. bunches, kb 62 592

Minimum bunch spacing ns 1350 99.8

* m 1.0 0.5 /0.55

Number of Pb ions/bunch 7 107 7 107

Transv. norm. RMS emittance m 1.5 1.5

Longitudinal emittance eV s/charge 2.5 2.5

Luminosity half-life (1,2,3 expts.)

h 14, 7.5, 5.5 8, 4.5, 3

J. Jowett, LHC Performance Workshop - Chamonix 2009

Only possibility for 2009-2010

Probably smaller!!


Analyses with the first PbPb collisions

•Quarkonia production yields and cross sections

•Quarkonia production suppression:• With respect to

– Beauty

– pp (RAA)

• As a function of– Centrality – Transverse momentum– Rapidity

•J/Ψ polarization

•v2 of J/ψ?

•Upsilon family?•CGC?


Quarkonia in PbPb collisions

J/ψ Υ

Mass resolution (MeV/c2)

~30 ~90



Counts 120k 900

Dielectron channel(nominal PbPb year)

J/ψ Υ

Mass resolution (MeV/c2) ~70 ~100



Counts (MB) 680k 6000

Dimuon channel


We have plenty of work to do