Quarkonium Workshop, BNL, June 6-18, 2011 1 Zebo Tang @ USTC Zebo Tang (for the STAR Collaboration)...
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Transcript of Quarkonium Workshop, BNL, June 6-18, 2011 1 Zebo Tang @ USTC Zebo Tang (for the STAR Collaboration)...
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
Quarkonium Workshop, BNL, June 6-18, 2011 2Zebo Tang @ USTC
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
Quarkonium Workshop, BNL, June 6-18, 2011 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
Quarkonium Workshop, BNL, June 6-18, 2011 4Zebo Tang @ USTC
STAR detector2 coverage at mid-rapidity (||<1)
TPC+BEMC+(MRPC-TOF)+(HLT) in this analysis
Quarkonium Workshop, BNL, June 6-18, 2011 5Zebo Tang @ USTC
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
Quarkonium Workshop, BNL, June 6-18, 2011 6Zebo Tang @ USTC
Electron ID (TPC+TOF)
dE/dx after TOF cut
Overall efficiency ~ 60%
Quarkonium Workshop, BNL, June 6-18, 2011 7Zebo Tang @ USTC
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)
Quarkonium Workshop, BNL, June 6-18, 2011 8Zebo 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
Quarkonium Workshop, BNL, June 6-18, 2011 9Zebo 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 spectraM. Bedjidian et al., hep-ph/0311048, and R. Vogt private communication
Quarkonium Workshop, BNL, June 6-18, 2011 11Zebo Tang @ USTC
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
Quarkonium Workshop, BNL, June 6-18, 2011 12Zebo 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)
Quarkonium Workshop, BNL, June 6-18, 2011 13Zebo 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)
Quarkonium Workshop, BNL, June 6-18, 2011 14Zebo 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
Quarkonium Workshop, BNL, June 6-18, 2011 15Zebo 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
Quarkonium Workshop, BNL, June 6-18, 2011 16Zebo Tang @ USTC
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
Quarkonium Workshop, BNL, June 6-18, 2011 17Zebo Tang @ USTC
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
Quarkonium Workshop, BNL, June 6-18, 2011 18Zebo Tang @ USTC
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
Quarkonium Workshop, BNL, June 6-18, 2011 19Zebo Tang @ USTC
High-pT J/ in d+Au
420 signals13
ZBT, QM2009
Significant signalStudy CNM effect at high pT
Quarkonium Workshop, BNL, June 6-18, 2011 20Zebo Tang @ USTC
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
Quarkonium Workshop, BNL, June 6-18, 2011 21Zebo Tang @ USTC
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
Quarkonium Workshop, BNL, June 6-18, 2011 22Zebo Tang @ USTC
MTD in RHICII era
J/
J/
MTD+HFT:Trigger and topologically reconstruct BJ/
MTD+TOF:J/+ccbar?Charmonium higher states? Υ
Thank you!
Quarkonium Workshop, BNL, June 6-18, 2011 24Zebo 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