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Exploring Quarkonium Production Mechanisms at STAR Collaboration Workshop

Investigating J/ψ production in p+p and A+A collisions to study color singlet vs. color octet mechanisms, feeddown, and deconfinement using experimental measurements and hadron correlations.

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Exploring Quarkonium Production Mechanisms at STAR Collaboration Workshop

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  1. J/y measurements at STAR Zebo Tang (for the STAR Collaboration) University of Science and Technology of China (USTC) Quarkonium Workshop, BNL, June 6-18, 2011

  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: • 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 Quarkonium Workshop, BNL, June 6-18, 2011

  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 Quarkonium Workshop, BNL, June 6-18, 2011

  4. STAR detector 2 coverage at mid-rapidity (|h|<1) TPC+BEMC+(MRPC-TOF)+(HLT) in this analysis Quarkonium Workshop, BNL, June 6-18, 2011

  5. Electron identification (TPC only) Note: electron yield is much less than hadrons x sigma deviation from electron dE/dx curve • With TPC only: • Difficult electron ID at low pT and high pT • Possible to get an electron sample with reasonable purity at intermediate pT Quarkonium Workshop, BNL, June 6-18, 2011

  6. dE/dx after TOF cut Electron ID (TPC+TOF) Overall efficiency ~ 60% Quarkonium Workshop, BNL, June 6-18, 2011

  7. (DhxDf=0.05x0.05) ~5X0 Electron ID (BEMC) • Online fast trigger: • Enhance high pT electron • Enhance recorded luminosity Offline cuts: Matching between EMC and TPC Deposited energy (BTOW) Shower shape (BSMD) High pT J/y: high pT electron (TPC+EMC) + Low/Intermediate pT electron (TPC only or TPC+TOF) Quarkonium Workshop, BNL, June 6-18, 2011

  8. 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 Quarkonium Workshop, BNL, June 6-18, 2011

  9. 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. CEM can reasonably explain the spectra M. Bedjidian et al., hep-ph/0311048, and R. Vogt private communication PHENIX: Phys. Rev. D 82, 012001 (2010) STAR: Phys. Rev. C80, 041902(R) (2009) Tsallis Blast-Wave model: ZBT et al., arXiv:1101.1912; JPG 37, 085104 (2010) Quarkonium Workshop, BNL, June 6-18, 2011

  10. J/y-hadron correlations Quarkonium Workshop, BNL, June 6-18, 2011

  11. PRC80, 041902(R), 2009 PLB200, 380, 1988 PLB370, 239, 1996 PRD71, 032001, 2005 EPJC71, 1575, 2011 R. 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 Quarkonium Workshop, BNL, June 6-18, 2011

  12. 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 Quarkonium Workshop, BNL, June 6-18, 2011

  13. 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) Quarkonium Workshop, BNL, June 6-18, 2011

  14. 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 Quarkonium Workshop, BNL, June 6-18, 2011

  15. 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)? Quarkonium Workshop, BNL, June 6-18, 2011

  16. Comparison See Rosi Reed’s talk for Upsilon results All suppressed in central heavy-ion collisions!! Similar suppression for STAR high-pT J/y and Upsilon Stronger suppression for high-pT J/y at CMS than at RHIC  Different rapidity range! Different pT range vs. beam energy! Quarkonium Workshop, BNL, June 6-18, 2011

  17. [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. J/y elliptic flow v2 Hao Qiu, QM2011 STAR Preliminary Consistent with zero Disfavor coalescence from thermalized charm quarks No regeneration? Regeneration only at low pT? Charm does not flow? Quarkonium Workshop, BNL, June 6-18, 2011

  18. Summary • In p+p collisions • J/y 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/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 Quarkonium Workshop, BNL, June 6-18, 2011

  19. ZBT, QM2009 420 signals 13 s High-pT J/y in d+Au Significant signal Study CNM effect at high pT Quarkonium Workshop, BNL, June 6-18, 2011

  20. 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 Reference data available from Fermi Lab Experiments and ISR Quarkonium Workshop, BNL, June 6-18, 2011

  21. Muon Telescope Detector (MTD) Lijuan Ruan, QM2011 Advantages over electrons no  conversion much less Dalitz decay contribution less affected by radiative losses in the materials Trigger capability for low to high pT J/ in central Au+Au collisions High m/hadron enhancement S/B~2 in central Au+Au Quarkonium Workshop, BNL, June 6-18, 2011

  22. J/ Υ J/ MTD in RHICII era MTD+HFT: Trigger and topologically reconstruct BJ/y MTD+TOF: J/y+ccbar? Charmonium higher states? Thank you! Quarkonium Workshop, BNL, June 6-18, 2011

  23. backup Quarkonium Workshop, BNL, June 6-18, 2011

  24. 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 Quarkonium Workshop, BNL, June 6-18, 2011

  25. Quarkonium Workshop, BNL, June 6-18, 2011

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