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STAR Heavy Flavor Measurements in Heavy-ion Collisions

W. Xie for STAR Collaboration (PURDUE University, West Lafayette). STAR Heavy Flavor Measurements in Heavy-ion Collisions. Outline : Quarkonia Measurements in p+p , d+Au and Au+Au collisions Open Charm Measurement D meson direct reconstruction. Non-photonic electron

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STAR Heavy Flavor Measurements in Heavy-ion Collisions

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  1. W. Xie for STAR Collaboration (PURDUE University, West Lafayette) STAR Heavy Flavor Measurements in Heavy-ion Collisions • Outline: • Quarkonia Measurements in • p+p, d+Au and Au+Au collisions • Open Charm Measurement • D meson direct reconstruction. • Non-photonic electron • Summary of the Present Results. • Future STAR Heavy Flavor Program. UIC HF Workshop 2012

  2. c c d Quarkonia Suppression: “Smoking Gun” for QGP • Low temperature • Vacuum J/y • High temperature • High density • (screening effect take place) d Sequential meltingaQGP thermometer H. Satz, NPA 783 (2007) 249c. D- D+

  3. c c c The life of Quarkoniain the Medium can be Complicated • Observed J/y is a mixture of direct production+feeddown (R. Vogt: Phys. Rep. 310, 197 (1999)). • All J/y ~ 0.6J/y(Direct) + ~0.3 cc + ~0.1y’ • B meson feed down. • Important to disentangle different component • Suppression and enhancement in the “cold” nuclear medium • Nuclear Absorption, Gluon shadowing, initial state energy loss, Cronin effect and gluon saturation (CGC) • Hot/dense medium effect • J/y,  dissociation, i.e. suppression • Recombination from uncorrelated charm pairs J/y D+

  4. Important to Study Open Heavy Flavor Production • A good reference to J/Ψ suppression or enhancement. • Same or similar initial state effect. • CGC, Shadowing, initial state energy loss, etc. • Large cross section (compared to J/ψ). • Probability for recombination. • Accurate reference measurements. • One of the important probes complimentary to J/ψ measurements • Interactions between heavy quark and medium are quite different from the ones for light quarks • gluon radiation, collisional energy loss, collisional disassociation, etc • allow further understanding of the medium properties.

  5. The STAR Detector EMC barrel MTD MRPC ToF barrel EMC End Cap FMS BBC FPD TPC FHC PMD FTPC Completed DAQ1000 Ongoing R&D HFT FGT HLT 6

  6. Signals Observed in STAR • STAR can measure heavy flavor • of all different kind • (J/ψ, D0, D*, electron …) • in broad pTrange. • at both mid and forward rapidity • in all collision species. D* p+p 200 GeV D0Au+Au 200 GeV forward J/ψ D* p+p 500 GeV

  7. STAR Charmonia Measurements e-/- e+/+

  8. J/y Suppression/Enhancement in 200GeV d+A and A+A and Collisions d+Au Collisions: • Nice consistency with PHENIX Cu+Cu Collisions: • RAA(p>5 GeV/c) = 1.4± 0.4±0.2 • RAA seems larger at higher pT. • Model favored by data: • 2-component: nucl-th/0806.1239 • Incl. color screening, hadron phase dissociation, coalescence, B feeddown. • Model unfavored by the data: • AdS/CFT+Hydro: JPG35,104137(2008) Phys.Rev.C80:041902,2009

  9. RAA vs. pT vs. Npart • Consistent with unity at high pT in (semi-) peripheral collisions • Systematically higher at high pTin all centralities • Suppression in central collisions at high pT • System size dependence due to J/y formation time effect? • Escaping at high pT? See HaoQiu’s talk this afternoon for details

  10. J/ z y x Yan,Zhuang,Xu PRL 97, 232301 (2006) J/y flow: more discriminating power PHENIX NPE v2: arXiv:1005.1627v2 • If charm quark flows. J/Psi from recombination also flow. • If the observation is consistent with zero flow, it could mean • J/psi does not flow OR • Flow is small due to mass ordering effect OR • Recombination is not a dominant process.

  11. J/y spectra in 200GeV Au+Au collisions • Broad pT coverage from 0 to 10 GeV/c • J/y spectra significantly softer than the prediction from light hadrons • Much smaller radial flow because it’s too heavy? • Regeneration at low pT? Phys. Rev. Lett. 98, 232301 (2007) See HaoQiu’s talk this afternoon for details

  12. J/y elliptic flow v2 STAR Preliminary disfavors the case that J/Ψ with pT > 2GeV/c is produced dominantly by coalescence from thermalized charm and anti-charm quarks. See HaoQiu’s talk this afternoon for details

  13. The sQGP is Complicated We thus need more probes, other than charms, to have a more complete picture of its properties, e.g. Upslions. • Cleaner Probes compared to J/psi: • recombination can be neglected at RHIC • Grandchamp, Sun, Van Hess, Rapp, PRC 73, 064906 (2006) • Final state co-mover absorption is small. STAR Preliminary STAR Preliminary STAR Preliminary See A. Kesich’s talk for details

  14. A Quick Glimpse of STAR Upsilon Measurements Models from M. Strickland and D. Bazow, arXiv:1112.2761v4 • Consistent with the melting of all excited states. See A. Kesich’s talk for details

  15. l STAR Open Charm Measurements K+ e-/- D0 K- + D0

  16. D0 and D* pT spectra in p+p 200 GeV D0 scaled by Ncc/ND0 = 1 / 0.56[1] D* scaled by Ncc/ND* = 1 / 0.22[1] Consistent with FONLL[2] upper limit. Xsec = dN/dy|ccy=0 × F × spp F = 4.7 ± 0.7 scale to full rapidity. spp(NSD) = 30 mb arXiv:1204.4244. [1] C. Amsler et al. (PDG), PLB 667 (2008) 1. [2] FONLL: M. Cacciari, PRL 95 (2005) 122001. • The charm cross section at mid-rapidity is: • The charm total cross section is extracted as: • b | 17

  17. D0 signal in Au+Au 200 GeV YiFei Zhang, JPG 38, 124142 (2011) • Year 2010 minimum bias 0-80% 280M Au+Au 200 GeV events. • 8-s signal observed. • Mass = 1863 ± 2 MeV (PDG value is 1864.5 ± 0.4 MeV) • Width = 12 ± 2 MeV 18

  18. Charm cross section vsNbin YiFei Zhang, JPG 38, 124142 (2011) arXiv:1204.4244. All of the measurements are consistent. Year 2003 d+Au : D0 + e Year 2009 p+p : D0 + D* Year 2010 Au+Au: D0 Assuming ND0 /Ncc = 0.56 does not change. Charm cross section in Au+Au 200 GeV: Mid-rapidity: 186 ± 22 (stat.) ± 30 (sys.) ± 18 (norm.) mb Total cross section: 876 ± 103 (stat.) ± 211 (sys.) mb [1] STAR d+Au: J. Adams, et al., PRL 94 (2005) 62301 [2] FONLL: M. Cacciari, PRL 95 (2005) 122001. [3] NLO:  R. Vogt, Eur.Phys.J.ST 155 (2008) 213    [4] PHENIX e: A. Adare, et al., PRL 97 (2006) 252002. Charm cross section follows number of binary collisions scaling => Charm quarks are mostly produced via initial hard scatterings. 19

  19. D0 RAA compared with Alice result YiFei Zhang, JPG 38, 124142 (2011) • ALICE results shows D meson is suppressed at high pT. • More luminosity and detector upgrade are needed from STAR to reach high pT. • At present, NPE is the key to study high pT charm and bottom production. A. Rossi, JPG 38, 124139 (2011) 20

  20. Non-photonic Electron Measurements DGLV: Djordjevic, PLB632, 81 (2006) BDMPS: Armesto, et al.,PLB637, 362 (2006) T-Matrix: Van Hees et al., PRL100,192301(2008). Coll. Dissoc. R. Sharma et al., PRC 80, 054902(2009). Ads/CFT: W. Horowitz Ph.D thesis. RL.+ Coll. J. Aichelin et al., SQM11 STAR: PRL 106, 159902 (2011) PHENIX: arXiv:1005.1627v2 • See M. Mustafa talk in the afternoon.

  21. Summary for the STAR Measurements • No suppression for J/psi at high pT (5-10 GeV/c) in 200GeV Cu+Cu and peripheral Au+Au collisions, • suppression at high pT in central Au+Aucollisions • J/psi suppression at high pT less than that at low pT • J/psi v2 measurements are consistent with zero, disfavor production at pT > 2 GeV/c dominated by coalescence from thermalized charm quarks • Upsilon measurement are consistent with 2S and 3S state melting.

  22. Summary for the STAR Measurements • The charm cross section per nucleon-nucleon 200 GeV collision at mid-rapidity • Charm cross sections at mid-rapidity follow number of binary collisions scaling, which indicates charm quarks are mostly produced via initial hard scatterings. • D0 nuclear modification factor RAA is measured. No obvious suppression observed at pT < 3 GeV/c. • Large suppression of high-pT non-photonic electron production is observed. • A real challenge to our understanding of energy loss mechanism. | | 23

  23. Future of Heavy Flavor Measurement at STAR MTD (MRPC) • See details in Yifei Zhang’s talk next

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  25. D0 signal in p+p 200 GeV arXiv:1204.4244. B.R. = 3.89% p+p minimum bias 105 M 4-s signal observed. Different methods reproduce combinatorial background. Consistent results from two background methods. 26

  26. D* signal in p+p 200 GeV arXiv:1204.4244. • Background recomstruction: • Wrong sign: • D0 and -, and + • Side band: • 1.72< M(K) < 1.80 or • 1.92 < M(K) < 2.0 GeV/c2 • Minimum bias 105M events in p+p 200 GeV collisions. • Two methods to reconstruct combinatorial background: wrong sign and side band. • 8-s signal observed. 27

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