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

J/ y production and correlation in p+p and Au+Au collisions at STAR. Zebo Tang (for the STAR Collaboration) University of Science and Technology of China (USTC). Motivation. J/ y production in p+p collisions: Baseline for A+A

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

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  1. J/y production and correlation in p+p and Au+Au collisions at STAR Zebo Tang (for the STAR Collaboration) University of Science and Technology of China (USTC) QM2011

  2. Motivation • J/y 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/y spectra • J/y-hadron correlation • J/y production in A+A collisions: • J/y 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 QM2011

  3. STAR, PRC80, 041902(R), 2009 Previous measurements at STAR • Spectra harder than CSM • Leave no room for feeddown in COM • First J/y-hadron correlation in p+p at RHIC • First estimation of BJ/y feeddown No suppression at high-pT in Cu+Cu collisions QM2011

  4. STAR detector 2 coverage at mid-rapidity (|h|<1) TPC+BEMC+(MRPC-TOF)+(HLT) in this analysis QM2011

  5. p+p, 2009 High-pT J/y signals TPC+BEMC+TOF TPC+BEMC for spectra TPC+BEMC+TOF for correlation Significantly reduced material in 2009 p+p and 2010 Au+Au collisions Clear signal in both p+p and Au+Au collisions High Signal/Background ratio in p+p allows correlation study QM2011

  6. J/y spectra in 200GeV p+p collisions Consistent 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 pT G. C. Nayak, M. X. Liu, and F. Cooper, Phys. Rev. D68, 034003 (2003), and private communication. PHENIX: Phys. Rev. D 82, 012001 (2010) STAR: Phys. Rev. C80, 041902(R) (2009) CEM can reasonably explain the spectra Tsallis Blast-Wave model: ZBT et al., arXiv:1101.1912; JPG 37, 085104 (2010) QM2011

  7. PRC80, 041902(R), 2009 PLB200, 380, 1988 PLB370, 239, 1996 PRD71, 032001, 2005 EPJC71, 1575, 2011 Ramona Vogt Workshop on Heavy Quark Production in Heavy-ion Collisions, Jan. 6, 2011, Purdue University (BJ/y)/ (inclusive J/y) • Extracted from near side J/y-h correlation • Consistent with previous results • No significant beam energy dependence • Can be used to constrain B production Based on decay kinematics etc in PYTHIA QM2011

  8. Away side associated hadron pT spectra STAR, PRL95, 152301 (2005) Consistent with hadron-hadron correlation away-side seems to come from gluon/light quark fragmentation QM2011

  9. J/y spectra in 200GeV Au+Au collisions • Good agreement between STAR and PHENIX • Significantly extend the pT range to 10 GeV/c • J/y spectra significantly softer than the prediction from light hadrons • Much smaller radial flow? • Regeneration at low pT? Phys. Rev. Lett. 98, 232301 (2007) Tsallis Blast-Wave model: ZBT et al., arXiv:1101.1912; JPG 37, 085104 (2010) QM2011

  10. RAA vs. 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 Increase from low pT to high pT Consistent with unity at high pT in (semi-) peripheral collisions More suppression in central than in peripheral even at high pT QM2011

  11. RAA vs. Npart 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 Systematically higher at high pT in all centralities Suppression in central collisions at high pT System size dependent due to J/y formation time effect? Escaping at high pT (without jet quenching effect)? QM2011

  12. 7.8fm 20-60% MB MB 7.8fm 20-40% 7.8fm J/y elliptic flow v2 Poster session 2, board# 60, Hao Qiu (for the STAR Collaboration) STAR Preliminary [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. Consistent with zero Disfavor coalescence from thermalized charm quarks QM2011

  13. Summary • In p+p collisions • J/y 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/y away side hadron production consistent with gluon / light quark fragmentation • In heavy-ion collisions • Observation of no suppression for J/yat 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/y suppression at high pT less than that at low pT • J/y v2 measurements are consistent with zero, disfavor coalescence from thermalized charm quarks • J/y spectra and v2 are consistent with J/y not participating in bulk flow QM2011

  14. 82±13 6s J/y in Au+Au @ BES 62 GeV Au+Au EMC Trigger 39 GeV Au+Au EMC Trigger 39 GeV Au+Au Min. Bias Trigger Clear signals seen in both 39 GeV and 62 GeV Au+Au collisions Thank you! Reference data available from Fermi Lab Experiments and ISR QM2011

  15. backup QM2011

  16. Sequential dissociation? Npart/2 • J/y spectra are modified in medium in Au+Au collisions • Spectra does not support scenario of large radial flow • RAA of high-pT J/y and Upsilon similar (poster: Rosi Reed for STAR) • J/y v2 consistent with zero, calescence from thermalized charm quarks unlikely 16 Zebo Tang, USTC QM2011

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