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High-p T J/ y production at STAR

The 2 nd Workshop on STAR-MTD Construction & Data Analysis Beijing, China, April 12 nd – April 13 th , 2012. High-p T J/ y production at STAR. Zebo Tang University of Science and Technology of China (USTC) Center of Particle Physics and Technology Lijuan Ruan

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High-p T J/ y production at STAR

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  1. The 2nd Workshop on STAR-MTD Construction & Data Analysis Beijing, China, April 12nd – April 13th, 2012 High-pT J/y production at STAR Zebo Tang University of Science and Technology of China (USTC) Center of Particle Physics and Technology Lijuan Ruan Brookhaven National Laboratory MTD workshop, THU, April 11-13, 2012

  2. Outline • Introduction and Motivation • Results in 200GeV p+p collisions • Results in 200GeV Au+Au collisions • Summary • Future with MTD MTD workshop, THU, April 11-13, 2012

  3. QCD phase diagram How do we know whether we have reached here or not? Net Baryon Density MTD workshop, THU, April 11-13, 2012

  4. J/y melting in QGP A. Mocsy J/y dissociation due to color screening  Signature of the QGP formation MTD workshop, THU, April 11-13, 2012

  5. J/y suppression at SPS and RHIC NA 50, PLB 477,28 (2000) M. Leitch SPS: Anomalous suppression  Significant evidence of deconfinement in central Pb+Pb RHIC: Similar suppression as SPS, more suppression at forward MTD workshop, THU, April 11-13, 2012

  6. High-pT J/y provides a cleaner probe Xingbo Zhao and Ralf Rapp, PRC82, 064905 LHC Yunpeng Liu, Nu Xu and Pengfei Zhuang, NPA834, 317c X. Zhao and R. Rapp, PRC82, 064905 • Nuclear absorption and life time (Cold Nuclear Matter effects) • RAA~0.5 at low pT, increase to unity at 5 GeV/c • Regeneration and radial flow only affect low pT • J/y measurements in Au+Au at RHIC limited at pT<5 GeV/c MTD workshop, THU, April 11-13, 2012

  7. Color octet Color singlet NRQCD J/y 3S1 J/y Production mechanism in p+p • Color singlet model (CSM),LO underpredicted CDF data by order of magnitude • Color octet model (COM), LO good agreement with CDF cross section disagreement with CDF polarization LO CDF measurement: PRL79,572 LO CSM LO COM MTD workshop, THU, April 11-13, 2012

  8. Color octet Color singlet NRQCD Charmonium production mechanism • Color singlet model (CSM),LO underpredicted CDF data by order of magnitude • Color octet model (COM), LO good agreement with CDF cross section disagreement with CDF polarization • CSM, NNLO* available • COM, NLO available • pQCD factorization see Jianwei Qiu’s talk LO More meaningful to test the theoretical calculations with high-pT J/y measurements

  9. Feeddown effects • y(2s): 7%-15%, slightly increase with pT • cc0,1,2: ~30%, slightly decrease with pT • B: Strong pT dependence CDF PRD71 MTD workshop, THU, April 11-13, 2012

  10. 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 MTD workshop, THU, April 11-13, 2012

  11. STAR detector 2 coverage at mid-rapidity (|h|<1) TPC+BEMC+(MRPC-TOF)+(HLT) in this analysis MTD workshop, THU, April 11-13, 2012

  12. 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 MTD workshop, THU, April 11-13, 2012

  13. 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) NLO NRQCD and pQCD factorization calculations will be available soon for comparison MTD workshop, THU, April 11-13, 2012

  14. J/y-hadron correlations MTD workshop, THU, April 11-13, 2012

  15. 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 MTD workshop, THU, April 11-13, 2012

  16. 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 MTD workshop, THU, April 11-13, 2012

  17. 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) MTD workshop, THU, April 11-13, 2012

  18. 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 MTD workshop, THU, April 11-13, 2012

  19. 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 Significant suppression in central Au+Au collisions for high-pT J/y Systematically higher at high pT in all centralities MTD workshop, THU, April 11-13, 2012

  20. 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 • Consistent with theoretical calculations including color screening effects MTD workshop, THU, April 11-13, 2012

  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 MTD workshop, THU, April 11-13, 2012

  22. J/ J/ J/y with MTD projection MTD+HFT: Trigger and topologically reconstruct BJ/y J/y-D correlation? MTD+TOF: J/y+ccbar? Charmonium higher states? MTD workshop, THU, April 11-13, 2012

  23. J/y with MTD at 2013 10 weeks Au+Au run Thank you! MTD workshop, THU, April 11-13, 2012

  24. backup MTD workshop, THU, April 11-13, 2012

  25. 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 MTD workshop, THU, April 11-13, 2012

  26. dE/dx after TOF cut Electron ID (TPC+TOF) Overall efficiency ~ 60% MTD workshop, THU, April 11-13, 2012

  27. (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) MTD workshop, THU, April 11-13, 2012

  28. 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 MTD workshop, THU, April 11-13, 2012

  29. MTD workshop, THU, April 11-13, 2012

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