QM2011 1Zebo Tang, USTC

Zebo Tang (for the STAR Collaboration)University of Science and Technology of China (USTC)

J/ production and correlation in p+p and Au+Au collisions at STAR

QM2011 2Zebo Tang, USTC

Motivation

J/ production in A+A collisions:• J/ only known probe to test deconfinement• Color screening in deconfined medium• Charm quark coalescence/recombination• Formation time effect at high-pT

Experimental measurements in different centralities:• Spectra and radial flow• Nuclear modification factor• Elliptic flow

J/ production in p+p collisions:• Baseline for A+A • Provide insight in production mechanism (Color-singlet vs. Color-octet)• Establish/Estimate feeddown Experimental measurements:• J/ spectra• J/-hadron correlation

QM2011 3Zebo Tang, USTC

Previous measurements at STAR

STAR, PRC80, 041902(R), 2009

Spectra harder than CSMLeave no room for feeddown in COM

First J/-hadron correlation in p+p at RHICFirst estimation of BJ/ feeddown

No suppression at high-pT in Cu+Cu collisions

QM2011 4Zebo Tang, USTC

STAR detector2 coverage at mid-rapidity (||<1)

TPC+BEMC+(MRPC-TOF)+(HLT) in this analysis

QM2011 5Zebo Tang, USTC

High-pT J/ signals

p+p, 2009

TPC+BEMC for spectraTPC+BEMC+TOF for correlation

TPC+BEMC+TOF

Significantly reduced material in 2009 p+p and 2010 Au+Au collisions Clear signal in both p+p and Au+Au collisionsHigh Signal/Background ratio in p+p allows correlation study

QM2011 6Zebo Tang, USTC

J/ spectra in 200GeV p+p collisionsConsistent with previous results

Good agreement between STAR and PHENIX

Color singlet model: direct NNLO still misses the high-pT part P. Artoisenet et al., Phys. Rev. Lett. 101, 152001 (2008),

and J.P. Lansberg private communication.

LO CS+CO: leave no room for feeddown at high pTG. C. Nayak, M. X. Liu, and F. Cooper, Phys. Rev. D68, 034003 (2003), and private communication.

Tsallis Blast-Wave model: ZBT et al., arXiv:1101.1912; JPG 37, 085104 (2010)

PHENIX: Phys. Rev. D 82, 012001 (2010)STAR: Phys. Rev. C80, 041902(R) (2009)

CEM can reasonably explain the spectra

PRC80, 041902(R), 2009

PLB370, 239, 1996PLB200, 380, 1988

PRD71, 032001, 2005EPJC71, 1575, 2011

QM2011 7Zebo Tang, USTC

(BJ/ / (inclusive J/

• Extracted from near side J/-h correlation• Consistent with previous results• No significant beam energy dependence• Can be used to constrain B production

Ramona Vogt

Workshop on Heavy Quark Production in Heavy-ion Collisions, Jan. 6, 2011, Purdue University

Based on decay kinematics etc in PYTHIA

QM2011 8Zebo Tang, USTC

Away side associated hadron pT spectra

Consistent with hadron-hadron correlation away-side seems to come from gluon/light quark fragmentation

STAR, PRL95, 152301 (2005)

QM2011 9Zebo Tang, USTC

J/ spectra in 200GeV Au+Au collisionsGood agreement between STAR and PHENIX

Significantly extend the pT range to 10 GeV/c

J/ spectra significantly softer than the prediction from light hadrons Much smaller radial flow? Regeneration at low pT?

Tsallis Blast-Wave model: ZBT et al., arXiv:1101.1912; JPG 37, 085104 (2010)

Phys. Rev. Lett. 98, 232301 (2007)

QM2011 10Zebo Tang, USTC

RAA vs. pT

Increase from low pT to high pT

Consistent with unity at high pT in (semi-) peripheral collisionsMore suppression in central than in peripheral even at high pT

STAR CuCu: PRC80, 014922(R)PHENIX: PRL98, 232301

Yunpeng Liu, Zhen Qu, Nu Xu and Pengfei Zhuang, PLB 678:72 (2009) and private comminication Xingbo Zhao and Ralf Rapp, PRC 82,064905(2010) and private communication

QM2011 11Zebo Tang, USTC

RAA vs. Npart

Systematically higher at high pT in all centralitiesSuppression in central collisions at high pT

System size dependent due to J/ formation time effect?Escaping at high pT (without jet quenching effect)?

Yunpeng Liu, Zhen Qu, Nu Xu and Pengfei Zhuang, PLB 678:72 (2009) and private comminication Xingbo Zhao and Ralf Rapp, PRC 82,064905(2010) and private communication

STAR Pion: Yichun Xu at QM2009

QM2011 12Zebo Tang, USTC

J/ elliptic flow v2

Poster session 2, board# 60, Hao Qiu (for the STAR Collaboration)

STAR Preliminary

Consistent with zeroDisfavor coalescence from thermalized charm quarks

[1] V. Greco, C.M. Ko, R. Rapp, PLB 595, 202.[2] L. Ravagli, R. Rapp, PLB 655, 126.[3] L. Yan, P. Zhuang, N. Xu, PRL 97, 232301.[4] X. Zhao, R. Rapp, 24th WWND, 2008.[5] Y. Liu, N. Xu, P. Zhuang, Nucl. Phy. A, 834, 317.[6] U. Heinz, C. Shen, priviate communication.

MB

7.8fm

7.8fm

MB

20-40%

20-60%7.8fm

QM2011 13Zebo Tang, USTC

Summary In p+p collisions

J/ spectra measurements are extended to high pT

Large S/B ratio allows correlation study B has sizeable (not dominant) contribution at high pT

High-pT J/ away side hadron production consistent with gluon / light quark fragmentation

In heavy-ion collisions Observation of no suppression for J/ at high pT (5-10 GeV/c) at STAR in 200GeV Cu+Cu and peripheral Au+Au collisions, And suppression at high pT in central Au+Au collisions J/ suppression at high pT less than that at low pT J/ v2 measurements are consistent with zero, disfavor coalescence from thermalized charm quarks J/ spectra and v2 are consistent with J/ not participating in bulk flow

QM2011 14Zebo Tang, USTC

82±136

J/ in Au+Au @ BES

Clear signals seen in both 39 GeV and 62 GeV Au+Au collisionsReference data available from Fermi Lab Experiments and ISR

62 GeV Au+AuEMC Trigger

39 GeV Au+AuEMC Trigger

39 GeV Au+AuMin. Bias Trigger

Thank you!

QM2011 15Zebo Tang, USTC

backup

QM2011 16Zebo Tang, USTC

Sequential dissociation?

Npart/2

• J/ spectra are modified in medium in Au+Au collisions• Spectra does not support scenario of large radial flow• RAA of high-pT J/ and Upsilon similar (poster: Rosi Reed for STAR)• J/ v2 consistent with zero, calescence from thermalized charm quarks unlikely