Quarkonia measurements at STAR

01/23/2009 Lijuan Ruan (heavy flavor workshop, UCLA) 1

Quarkonia measurements at STAR Lijuan Ruan (for the STAR Collaboration)

(Brookhaven National Laboratory)

Outline: •  Motivation and introduction

•  J/ψ results

•  Υ results

•  Summary and outlook


High pT J/ψ in heavy ion collisions

J/ψ H.Satz,Nucl.Phys.A(783):249‐260(2007)

J/ψ suppression at low pT maybe from excited stats (ψ’, χc) F. Karsch, D. Kharzeev and H. Satz, PLB 637, 75 (2006)

Hot wind dissociation high pT direct J/ψ suppression

2-component approach: dissociation + recombination RAA decreases slightly or flat with pT X. Zhao and R. Rapp, hep-ph/07122407 RAA increase slightly with pT including formation time and B decay X. Zhao, WWND2008

Color singlet model: RAA increase with pT (formed out of medium) K. Farsch and R. Petronzio, PLB 193(1987), 105 ; J.P. Blaizot and J.Y. Ollitrault, PLB 199(1987),499

Hot wind dissociation

H. Liu, K. Rajagopal and U.A. Wiedemann PRL 98, 182301(2007) and hep-ph/0607062 M. Chernicoff, J. A. Garcia, A. Guijosa hep-th/0607089

T. Gunji, QM08


Quarkonium production mechanism in p+p

1.  Color singlet model (CSM) 1) pQCD 2.  Color octet model (COM) 2) NRQCD 3.  Color evaporation model (CEM) 3)

4.  … Contribution might from: •  Gluon fusion •  Heavy quark fragmentation 4)

•  Gluon fragmentation 5)

•  Decay feed-down •  … How do we distinguish different production mechanism and different source contribution?

1) R. Baier et al., PLB 102, 364 (1981)

2) M. Kramer, Progress in Particle and Nuclear Physics 47, 141 (2001) 3) H. Fritzsch, PLB 67, 217 (1977)

4) Cong-Feng Qiao, hep-ph/0202227

5) K. Hagiwara et al., hep-ph/0705.0803

NRQCD

What’s the production mechanism at RHIC energy?


RPSD

PMD

FPD

FMS

EMC barrel

EMC End Cap

FGT

Complete

Ongoing

MTD (BNL LDRD)

R&D HFT

TPC

The STAR Detector

Run8: without any inner tracker


Low pT J/ψ in p+p and Cu+Cu at 200 GeV J/ψ trigger 0 < pT < 5.5 GeV/c

MCdescribespositionandwidth

p+p 200 GeV

Cu+Cu 200 GeV

STAR Preliminary

J/ψe+e-


High pT J/ψ in p+p at 200 GeV J/ψ pT

J/ψ pT

EMC+TPC electrons: |η|<1, pT>2.5 GeV/c

TPC only electrons: |η|<1, pT>1.2 GeV/c

EMC+TPC electrons: |η|<1, pT>4.0 GeV/c

TPC only electrons: |η|<1, pT>1.2 GeV/c

No background at pT>5GeV/c

Reach higher pT (~14GeV/c)

p+p 2005

p+p 2006

(S+B)/B: 24/2

(S+B)/B: 54/14

EMC trigger

3 pb-1

11 pb-1


J/ψ spectra in p+p and Cu+Cu at 200 GeV

•  Significantly extend pT range of previous measurements in p+p at RHIC to 14 GeV/c

•  Agreement of charm measurements between STAR and PHENIX

•  Consistent with Color Evaporation calculations (R. Vogt, Private communication)


xT scaling in p+p collisions

n is related to the number of point-like constituents taking an active role in the interaction

n=8: diquark scattering

n=4: QED-like scattering

xT scaling: 1.  π and proton at pT>2 GeV/c: n=6.5±0.8 PLB 637, 161(2006) 2.  J/ψ at high pT: n=5.6±0.2 J/ψ production: closer to 22 scattering 3. Soft processes affect low pT J/ψ production


Nuclear modification factor RAA

•  Double the pT range to 10GeV/c

•  Consistent with no suppression at high pT: RAA(pT>5 GeV/c) = 0.9±0.2

•  Indicates RAA increase from low pT to high pT

•  Contrast to AdS/CFT prediction

•  Formed out of medium? Affect by heavy quark/gluon energy loss

•  Decay from other particles?

2-component Approach predicted slightly increase RAA after more consideration X. Zhao, WWND2008


Disentangle contributions via Correlations

•  J/ψ-hadron correlation can also shed light on different source contribution to J/ψ production

•  May be used to distinguish CSM and COM

1)

no near side correlation

2)

strong near side correlation UA1:PLB 200, 380(1988) and PLB 256,112(1991)


J/ψ-hadron correlation

Heavy quark fragmentation

Near side correlation

Good S/B ratio makes this measurement possible

STAR Preliminary


J/ψ-hadron correlation in p+p

PRL 95,152301(2005)

h-h correlation •  No significant near side J/ψ-hadron azimuthal angle correlation

•  Constrain B meson’s contribution to J/ψ yield

•  Hints of CSM?


Constrain bottom yields

•  pQCD predicts significant BJ/Ψ •  correlations shows low B contribution •  can used to further constrain B yields

•  constrain correlation from jet fragmentation

STAR Preliminary


Yields in near/away side

Associated hadron spectra with leading J/ψ: •  Away side: Consistent with leading charged hadron correlation measurement (h-h) away-side from gluon or light quark fragmentation •  Near side: Consistent with no associated hadron production BJ/ψ not a dominant contributor to inclusive J/ψ constrain J/ψ production mechanism


J/ψ+ccbar production puzzle

Belle, PRL 89, 142001(2002)

e+e-, 10.6 GeV

0.82 ±0.15 ± 0.14 from new analysis.

While CEM predict 0.049 D. Kang, et al., PRD 71, 094019 and hep-ph/0412381

T. Uglov, EPS 2003

The higher order contribution is significant and can not be neglected.

(e+e- J/ψ +cc)/(e+e- J/ψ + X) = 0.59+0.15-0.13 ±0.12

NRQCD predict ~0.1 K. Liu and Z. He, PRD 68, 031501 (2003)

B.L. Loffe and D.E. Kharzeev PRD 69, 014016 (2004)


CSM with kt-factorization

CSM can also describe the data with some improvement like the kt-factorization approach

PHENIX, PRL 92, 05180 (2004)

S.P. Baranov and A. Szczurek arXiv:0710.1792

CSM NLO correction is huge CSM NNLO correction is significant for Υ: Jean-Phillippe Lansberg

dσ/d

p T [n

b/(G

eV/c

)]

pT (GeV/c)

Color singlet LHC 14 TeV

Tevatron 1.96 TeV LO NLO

PRL98, 252002(2007)


Υ results: p+p and Au+Au at 200 GeV

•  Υ (1S+2S+3S) total yield: integrated from 7 to 11 GeV from background-subtracted mee distribution

•  Peak width consistent with expected mass resolution •  Significance of signal is 3-4σ •  Note: Contribution from Drell-Yan (~9%) not subtracted

preliminary


preliminary

STAR 2006 √s=200 GeV p+p ϒ+ϒ′+ϒ″→e+e- cross section consistent with pQCD and world data

RAA in progress

Bee×(dσ/dy)y=0=91±28(stat.)±22(syst.)pb

Υ results: p+p


Summary

J/ψ in p+p and Cu+Cu collisions: pT spectra in p+p: •  extended to ~14 GeV/c •  follows xT scaling with n=5.6 at pT>5

GeV/c J/ψ-hadron azimuthal correlation in p+p: •  no significant near side correlation

constrain the contribution from BJ/ψ+X

•  away-side spectra consistent with h-h correlation gluon or light quark

fragmentation J/ψ RAA •  indication of RAA increasing at high pT

Υ in p+p and Au+Au collisions: •  p+p results: consistent with pQCD and world data; RAA in progress

production mechanisms: •  described by CEM and CSM •  soft processes affect low pT

production

•  constrain decay contribution •  constrain J/ψ production from

jet contribution (heavy flavor and gluon)

•  constrain production mechanism: CSM or COM

•  medium properties


ϒ and high-pt J/ψ in run8 dAu

dAu data sampled luminosity: 31 nb-1

STAR Preliminary

STAR Preliminary

STAR Preliminary

p+p equivalent: 13pb-1

STAR Preliminary • J/ψ spectra • J/ψ-h correlation • Isolated J/ψ • ψ(2S) • χc

STAR Preliminary


Future dramatic improvement of J /ψ at low pT

EMC+TOF+HFT (large acceptance): •  J/ψ production •  Different states predicted to melt at

different T in color medium •  Charmonia (J/ψ), bottonia (ϒ)

Quarkonium dissociation temperatures – Digal, Karsch, Satz

pT (e)>1.5 GeV/c

PHENIX Acceptance: |η|<0.35, φ=2*π/2 STAR TOF-Upgrade Acceptance: |η|<0.9, φ=2*π

J/ψ yields from 1 billion minbias Au+Au events: 43.8x10-9/0.040x109*292*0.5*1.8*0.5= 144,0000.3% v2 error σJ/ψ σpp N Nbin ε y RAA

dE/dx after TOF cut


High luminosity for Υ & high-pT J/ψ

RHIC II + DAQ1000: Time-Of-Flight: Electron identification Enhance statistics


Detector upgrades: HFT and MTD

Heavy Flavor Tracker:

Muon Telescope Detector:

nσπ>0

STAR Preliminary

Prototype in run VII

γe+e- rejection

Topologically reconstruct J/ψ from B decay

Rejection power: ~16

Muon identification simulation


Backup


Datasets

p+p data sample:   1. EMC triggered events in year 2005 ET>3.5 GeV Integrated luminosity: 3 (pb)-1

  2. EMC triggered events in year 2006 ET>5.4 GeV Integrated luminosity: 11 (pb)-1

Cu+Cu data sample:   1. EMC triggered events in year 2005 ET>3.75 GeV Integrated luminosity: 0.9 (nb)-1

pp-equivalent: 3 (pb)-1

High-pT J/ψ p+p data sample: •  1. J/ψ triggered events in year 2006 •  Integrated luminosity: 377 (nb)-1

•  2. Υ triggered events in year 2006 •  Integrated luminosity: 9(pb)-1

Au+Au data sample: •  1. Υ triggered events in year 2007 Integrated luminosity: 300(µb)-1

pp-equivalent: 12(pb)-1

Triggered data

Quarkonia measurements at STAR

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