Quarkonium Workshop, BNL, June 6-18, 2011 1 Zebo Tang @ USTC Zebo Tang (for the STAR Collaboration) University of Science and Technology of China (USTC)

Quarkonium Workshop, BNL, June 6-18, 2011 1Zebo Tang @ USTC

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

J/ measurements at STAR


Motivation

J/ production in A+A collisions:• Quarkonium 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


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


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

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


Electron identification (TPC only)

With TPC only:• Difficult electron ID at low pT and high pT

• Possible to get an electron sample with reasonable purity at intermediate pT

x sigma deviation from electron dE/dx curve

Note: electron yield is much less than hadrons


Electron ID (TPC+TOF)

dE/dx after TOF cut

Overall efficiency ~ 60%


Electron ID (BEMC)

Online fast trigger: • Enhance high pT electron• Enhance recorded luminosity

Offline cuts:Matching between EMC and TPCDeposited energy (BTOW)Shower shape (BSMD)

x0.05x0.05)

~5X0

High pT J/high pT electron (TPC+EMC) +Low/Intermediate pT electron (TPC only or TPC+TOF)


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


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 spectraM. Bedjidian et al., hep-ph/0311048, and R. Vogt private communication


J/-hadron correlations


PRC80, 041902(R), 2009

PLB370, 239, 1996PLB200, 380, 1988

PRD71, 032001, 2005EPJC71, 1575, 2011

(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

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


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)


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)


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


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


Comparison

All suppressed in central heavy-ion collisions!!Similar suppression for STAR high-pT J/ and UpsilonStronger suppression for high-pT J/ at CMS than at RHIC Different rapidity range! Different pT range vs. beam energy!

See Rosi Reed’s talk forUpsilon results


J/ elliptic flow v2

[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.

Hao Qiu, QM2011

Consistent with zeroDisfavor coalescence from thermalized charm quarks No regeneration? Regeneration only at low pT? Charm does not flow?

STAR Preliminary


Summary

In p+p collisions J/ spectrum 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


High-pT J/ in d+Au

420 signals13

ZBT, QM2009

Significant signalStudy CNM effect at high pT


82±136

J/ in Au+Au @ BES

Clear signals seen in both 39 GeV and 62 GeV Au+Au collisions

Reference data available from Fermi Lab Experiments and ISR

62 GeV Au+AuEMC Trigger

39 GeV Au+AuEMC Trigger

39 GeV Au+AuMin. Bias Trigger


Muon Telescope Detector (MTD)

Advantages over electronsno conversionmuch less Dalitz decay contributionless affected by radiative losses in the materials

Trigger capability for low to high pT J/ in central Au+Au collisionsHigh /hadron enhancement

S/B~2 in central Au+Au

Lijuan Ruan, QM2011


MTD in RHICII era

J/

J/

MTD+HFT:Trigger and topologically reconstruct BJ/

MTD+TOF:J/+ccbar?Charmonium higher states? Υ

Thank you!


backup


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


Documents

Quarkonium Workshop, BNL, June 6-18, 2011 1 Zebo Tang @ USTC Zebo Tang (for the STAR Collaboration) University of Science and Technology of China (USTC)