1. Charm Production from STAR Experiment 1 Outline :  STAR Present Measurements  J/ψ 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. 05/15/2012Berkeley School 2012 W. Xie for STAR Collaboration (PURDUE University, West Lafayette)

2. Motivation for Studying Heavy Quarks Heavy quark mass are external parameter to QCD. Sensitive to initial gluon density and gluon distribution. Interact with the medium differently from light quarks. Suppression or enhancement pattern of heavy quarkonium production reveals critical features of the medium. Cold Nuclear effect (CNM): – Different scaling properties in central and forward rapidity region CGC. – Gluon shadowing, etc 2 D0D0 K+K+  l K-K- e-/-e-/- e-/-e-/- e+/+e+/+ Heavy quarkonia Open heavy flavor Non-photonic electron

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4. Quarkonia Suppression: “Smoking Gun” for QGP 4 cc J/  D+D+ d Low temperature Vacuum High temperature High density (screening effect take place) Sequential melting  a QGP thermometer H. Satz, NPA 783 (2007) 249c. d D-D-

5. The life of Charmonia in the Medium can be Complicated 5 Observed J/  is a mixture of direct production+feeddown ( R. Vogt: Phys. Rep. 310, 197 (1999)). – All J/  ~ 0.6J/  (Direct) + ~0.3  c + ~0.1  ’ –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/   dissociation, i.e. suppression – Recombination from uncorrelated charm pairs D+D+ cc c J/ 

6. Important to Study Open Charm 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). 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. 6

7. 7 The STAR Detector 7 MRPC ToF barrel BBC PMD FPD FMSFMS EMC barrel EMC End Cap DAQ1000 Completed TPC FTPC FGT Ongoing R&D FHC HLT HFT MTD

8. 8 The (major) STAR Detector for Charm Measurements 8

9. 9 Particle Identification from TOF+dE/dx |1/  -1|<0.03  Extend hadron PID to intermediate p T Important for open charm measurements.  TOF/TPC allows electron PID down to very low momentum  Important for charmonia measurements.

10. 10 Electron Identification from TPC + BEMC High pT electron PID:  TPC+BTOW:  Associate TPC tracks with BTOW clusters.  cut p/E ~1.0  Cut on number of BSMD strips per cluster:  Associate TPC tracks with BSMD clusters.  Higher for electron. 2.5 < pT<3.0 GeV/c8.0< pT<10 GeV/c

11. Charm Signals Observed in STAR 11 STAR can measure charm of all different kind (J/ψ, D0, D*, electron …) in broad pT range. at both mid and forward rapidity in all collision species. STAR Preliminary forward J/ψ J/ψ from χ c enriched STAR Preliminary D 0 Au+Au 200 GeV D* p+p 200 GeV D* p+p 500 GeV

12. STAR Charmonia Measurements 12 e-/-e-/- e+/+e+/+

13. J/  Production in 200GeV p+p Collisions 13 Color singlet model (NNLO*CS):  P. Artoisenet et al., PRL. 101, 152001 (2008), and J.P. Lansberg private communication.  Include no feeddown from higher mass state. LO CS+ color octet (CO):  G. C. Nayak et al., PRD 68, 034003 (2003), and private communication.  Include no feeddown from higher mass state.  Agree with the data Color Evaporation Model:  M. Bedjidian et al., hep-ph/0311048; R. Vogt private communication  Include feeddown from Xc and ψ’  Agree with the data STAR: Phys. Rev. C80, 041902(R) (2009) Tsallis Blast-Wave model: ZBT et al., arXiv:1101.1912; JPG 37, 085104 (2010) Zebo Tang, JPG 38, 124107 (2011)

14. J/  -hadron Azimuthal Correlation in 200GeV p+p Collisions 14  B  J/  10-20% of total J/  (pT > 4GeV/c) at RHIC  The ratio has no significant dependence on collisions energy.  Constrain J/  Production mechanisms in p+p:  J/  +c, J/  +D or J/  +e S. Brodsky, J.-P. Lansberg, arXiv:0908.0754 Zebo Tang, JPG 38, 124107 (2011)

15. Away side associated hadron p T spectra 15 Consistent with hadron- hadron correlation  away-side seems to come from gluon/light quark fragmentation STAR, PRL95, 152301 (2005) Zebo Tang, JPG 38, 124107 (2011) E. Braaten Phys. Rev. Lett. 71, 1673 (1993).

16. J/  Polarization 16  On top of spectra, J/psi polarization provide additional discrimination power against models.  Results are consistent with the COM and NLO + CSM prediction. Much more statistics are needed. pT (J/psi: GeV/c) See Barbara Trzeciak’s talk for details. Helicity frame

17. J/  Suppression/Enhancement in 200GeV d+A and A+A and Collisions d+Au Collisions: Nice consistency with PHENIX Cu+Cu Collisions:  R AA (p  >5 GeV/c) = 1.4± 0.4±0.2  R AA 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) 17 Phys.Rev.C80:041902,2009

18. J/  spectra in 200GeV Au+Au collisions 18 Broad pT coverage from 0 to 10 GeV/c J/  spectra significantly softer than the prediction from light hadrons  Much smaller radial flow?  Regeneration at low p T ? Tsallis Blast-Wave model: ZBT et al., arXiv:1101.1912; JPG 37, 085104 (2010) Phys. Rev. Lett. 98, 232301 (2007) Zebo Tang, JPG 38, 124107 (2011)

19. R AA vs. p T 19 Increase from low p T to high p T Consistent with unity at high p T in (semi-) peripheral collisions More suppression in central than in peripheral even at high p T 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 Zebo Tang, JPG 38, 124107 (2011)

20. R AA vs. Npart 20 Systematically higher at high p T in all centralities Suppression in central collisions at high p T System size dependence due to J/  formation time effect? Escaping at high p T ? 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 Zebo Tang, JPG 38, 124107 (2011)

21. 21 J/ flow: more discriminating power  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. Yan,Zhuang,Xu PRL 97, 232301 (2006) J/  PHENIX NPE v2: arXiv:1005.1627v2 x y z

22. STAR Preliminary J/  elliptic flow v 2 22  V 2 (hadron) > V 2 (Φ) > v 2 (J/ψ) ~0.  Is it completely due to mass ordering effect? Zebo Tang, JPG 38, 124107 (2011)

23. STAR Preliminary Zebo Tang, JPG 38, 124107 (2011) J/  elliptic flow v 2 23 [1] V. Greco, C.M. Ko, R. Rapp, PLB 595, 202 (minbias) [2] L. Ravagli, R. Rapp, PLB 655, 126.(minbias) [3] L. Yan, P. Zhuang, N. Xu, PRL 97, 232301. (b =7.8 fm) [4] X. Zhao, R. Rapp, 24th WWND, 2008. (20-40%) [5] Y. Liu, N. Xu, P. Zhuang, Nucl. Phy. A, 834, 317. (b = 7.8 fm) [6] U. Heinz, C. Shen, priviate communication. (20-60%) disfavors the case that J/Ψ with pT > 2GeV/c is produced dominantly by coalescence from thermalized charm and anti- charm quarks. Models P-value Initially produced1.8/3 6.2e-1 Coalescence at freezeout22.6/3 4.9e-5 Coalescence In transport13.9/3 3.0e-3 Coalescence In fireball4.8/3 1.8e-1 Coalescence +initial mix2.9/3 4.0e-1 Coalescence +initial mix1.8/4 7.7e-1 Hydro T=120 w/viscosity16.5/39.2e-4 Hydro T=165w/ viscosity14.9/31.9e-03 Hydro T=120 w/o viscosity191.6/32.7e-41 Hydro T=165w/o viscosity237.3/30.0 Courtesy of Hao Qiu

24. STAR Open Charm Measurements 24 D0D0 K+K+  l K-K- e-/-e-/- D0D0

25. 25 D 0 signal in p+p 200 GeV B.R. = 3.89% p+p minimum bias 105 M 4- signal observed. Different methods reproduce combinatorial background. Consistent results from two background methods. arXiv:1204.4244.

26. 26 D* signal in p+p 200 GeV Minimum bias 105M events in p+p 200 GeV collisions. Two methods to reconstruct combinatorial background: wrong sign and side band. 8- signal observed. arXiv:1204.4244.

27. 27 D 0 and D* p T spectra in p+p 200 GeV [1] C. Amsler et al. (PDG), PLB 667 (2008) 1. [2] FONLL: M. Cacciari, PRL 95 (2005) 122001. arXiv:1204.4244. D 0 scaled by N cc / N D0 = 1 / 0.56 [1] D* scaled by N cc / N D* = 1 / 0.22 [1] Consistent with FONLL [2] upper limit. Xsec = dN/dy| cc y=0 × F ×  pp F = 4.7 ± 0.7 scale to full rapidity.  pp (NSD) = 30 mb

28. 28 D 0 signal in Au+Au 200 GeV  Year 2010 minimum bias 0-80% 280M Au+Au 200 GeV events.  8- signal observed.  Mass = 1863 ± 2 MeV (PDG value is 1864.5 ± 0.4 MeV)  Width = 12 ± 2 MeV YiFei Zhang, JPG 38, 124142 (2011)

29. 29 Charm cross section vs N bin Charm cross section follows number of binary collisions scaling => Charm quarks are mostly produced via initial hard scatterings. All of the measurements are consistent. Year 2003 d+Au : D 0 + e Year 2009 p+p : D 0 + D* Year 2010 Au+Au: D 0 Assuming N D0 / N cc = 0.56 does not change. Charm cross section in Au+Au 200 GeV: Mid-rapidity: 186 ± 22 (stat.) ± 30 (sys.) ± 18 (norm.) b Total cross section: 876 ± 103 (stat.) ± 211 (sys.) b [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. YiFei Zhang, JPG 38, 124142 (2011) arXiv:1204.4244.

30. 30 √s NN Charm cross section vs √s NN Compared with other experiments, provide constraint for theories. YiFei Zhang, JPG 38, 124142 (2011)

31. 31 D 0 R AA 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)

32. 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 32  Models with different or similar mechanisms can or can not describe the data  Which one is right and what are missing? Charm dominate at pT<5 GeV/c STAR: PRL 106, 159902 (2011) PHENIX: arXiv:1005.1627v2

33. Summary for the Present STAR Charmonia Measurements 33  In p+p collisions  J/  spectra measurements are extended to high p T  J/  polarization is consistent with COM and NLO + CSM prediction  Large S/B ratio allows correlation study o B has sizeable (not dominant) contribution at high p T o High-p T J/  away side hadron production consistent with gluon / light quark fragmentation  In heavy-ion collisions  Observation of no suppression for J/  at high p T (5-10 GeV/c) at STAR in 200GeV Cu+Cu and peripheral Au+Au collisions, and suppression at high p T in central Au+Au collisions J/  suppression at high p T less than that at low p T  J/  v 2 measurements are consistent with zero, disfavor production at pT > 2 GeV/c dominated by coalescence from thermalized charm quarks

34. 34  D 0 and D* are measured in p+p 200 GeV up to p T = 6 GeV/c.  D 0 is measured in Au+Au 200 GeV up to p T = 5 GeV/c.  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.  D 0 nuclear modification factor R AA is measured. No obvious suppression observed at p T < 3 GeV/c.  Large suppression of high-pT non-photonic electron production is observed. A real challenge to our understanding of energy loss mechanism. Summary for the Present STAR Open Charm Measurements

35. STAR Preliminary The sQGP is Complicated 35 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. Anthony Kesich, WWnd2012

36. A Quick Glimpse of STAR Upsilon Measurements 36 0-10% Centrality STAR Preliminary S. Digal, P. Petreczky, and H. Satz, Phys Rev. D 64,094015 (2001) Anthony Kesich, WWnd2012  Consistent with the melting of all excited states.

37. Questions to be addressed by STAR in the next Decade. 37 (http://www.bnl.gov/npp/docs/STAR_Decadal_Plan_Final%5B1%5D.pdf)

38. 38 How to address these questions At both low pT and high pT

39. Heavy Flavor Tracker (HFT) 39 TPC Volume Outer Field Cage Inner Field Cage FGT SSD IST PXL HFT Detector Radius (cm) Hit Resolution R/  - Z (  m -  m) Radiation length SSD2230 / 8601% X 0 IST14170 / 18001.32 %X 0 PIXEL 88 / 8~0.37 %X 0 2.58 / 8~0.37% X 0 SSD existing single layer detector, double side strips (electronic upgrade) IST one layer of silicon strips along beam direction, guiding tracks from the SSD through PIXEL detector. - proven strip technology Prototype for run2013 and complete for run2014 PIXEL double layers 18.4x18.4 m pixel pitch 2 cm x 20 cm each ladder 10 ladders, delivering ultimate pointing resolution. new active pixel technology

40. Muon Telescope Detector (MTD) 40 Use the magnet steel as absorber and TPC for tracking. covers the whole iron bars and leave the gaps in-between uncovered. Acceptance: |  |<0.5 and 45% in azimuth 118 modules, 1416 readout strips, 2832 readout channels Long-MRPC detector technology, HPTDC electronics (same as STAR-TOF) ~43% for run2013 and Complete for run2014

41. 41 RHIC CAD Projections http://www.bnl.gov/npp/docs/pac0611/Fischer_Machine%20performance%20and%20projections.pdf

42. Production and flow of Directly Reconstructed Charm 42 R CP =a*N 10% /N (60-80)%  Assuming D 0 R cp distribution as charged hadron  Assuming D 0 v 2 distribution from quark coalescence.  500M minbias events.  STAR duty factor: 50% (underestimated).  Efficiency of |Vz|<5cm: 20%.  50 kHz collision rate at RHIC-II and 500 Hz bandwidth for minbias trigger

43. Access Bottom Production via Electrons 43 Curves: H. van Hees et al. Eur. Phys. J. C 61 (2009) 799  (Be) spectra obtained via the subtraction of charm decay electrons from inclusive NPEs: no model dependence  500M minbias events for low pT  500 µb -1 sampled Luminosity for high pT  corresponding to 5 nb -1 RHIC delivered luminosity

44. B  J/  + X with HFT+TPC+MTD 44 Prompt J/ J/ from B  Cleanest sample of B meson decays.  B  J/ψ  ee suffer from low trigger efficiency.  A much better measurements: B  J/ψ->µµ not limited by triggers Less multiple scattering, leading to higher B meson ID efficiency.

45. Projections on J/ψ Measurements 45 J/   µµ (delivered) Zebo Tang, JPG 38, 124107 (2011)

46. Upsilon Mass Resolution with MTD 46 Di-electrons with inner tracker Di-electrons without inner tracker. Di-muons from any case

47. Projections on Upsilon Measurements 47

48. Charm Baryons 48  c pK Lowest mass charm baryons c = 60 m  c /D enhancement?  0.11 (pp PYTHIA)  0.4-0.9 (Di-quark correlation in QGP) S.H. Lee etc. PRL 100 (2008) 222301  Total charm yield in heavy ion collisions

49. QGP Thermal Radiation with dileptons 49 search for QGP thermal radiations dominated by the correlated pair from charm-decay electrons. Addressed by e  correlation with Muon Telescope Detector at STAR from ccbar: S/B=2 (M eu >3 GeV/c 2 and p T (e  )<2 GeV/c) S/B=8 with electron pairing and tof association Accurate D meson measurements L. Ruan et al., JPG 36 (2009) 095001 J. Zhao, JPG 38, 124134 (2011)

50. Summary 50  Precision measurements of J/ψ will continue to be one of the most important tasks in the field  Precision measurements of other heavy flavor probes are a necessary condition for a complete understanding of the interaction between heavy quarks and the Medium.  STAR HFT and MTD upgrades together with existing subsystems and RHIC II luminosities will provide us with the unprecedented opportunity to accomplish these tasks.  The accomplishment of these tasks will allow us to better understand the medium properties, which may leads to new discoveries.

51. BACKUP SLIDES 51

52. Charm Quark Hadronization 52 Lee, et. al, PRL 100 (2008) 222301 Direct (hard) fragmentation in elementary collisions. However, in heavy ion collisions … V. Greco et al., PLB 595(2004)202 Coalescence approach Charm baryon enhancement ? - coalescence of c and di-quark

53. Reconstruction of Displaced Vertices 53 D 0 decays particle c  (  m) Mass (GeV) D0D0 1231.865 D+D+ 3121.869 Ds+Ds+ 1501.968 c+c+ 602.286 B0B0 4595.279 B+B+ 4915.279 Direct topological reconstruction of charm and bottom decays

54. Efficiency / Significance 54 Need New plots D 0 spectrum covering 0.5 - ~10 GeV/c in one RHIC run

55. STAR HFT vs. PHENIX VTX 55

56. Upsilon Statistics 56 Collision system Delivered lumi. 12 weeks Sampled lumi. 12 weeks (70%) Υ countsMin. lumi. precision on Υ (3s) (10%) Min. lumi. precision on Υ (2s+3s) (10%) 200 GeV p+p 200 pb -1 140 pb -1 390420 pb -1 140 pb -1 500 GeV p+p 1200 pb -1 840 pb -1 6970140 pb -1 50 pb -1 200 GeV Au+Au 22 nb -1 16 nb -1 177010 nb -1 3.8 nb -1 Delivered luminosity: 2013 projected; Sampled luminosity: from STAR operation performance

57. Some pixel features and specifications 57 Pointing resolution(12  19GeV/p  c)  m LayersLayer 1 at 2.5 cm radius Layer 2 at 8 cm radius Pixel size18.4  m X 18.4  m Hit resolution8  m rms Position stability6  m (20  m envelope) Radiation thickness per layer X/X 0 = 0.37% Number of pixels436 M Integration time (affects pileup) 0.2 ms Radiation requirement20-90 kRad Rapid detector replacement < 8 Hours critical and difficult more than a factor of 3 better than other vertex detectors (ATLAS, ALICE and PHENIX)

58. MTD (Run 10 Prototype) Performance 58 Total resolution: 109 ps MTD intrinsic resolution: 96 ps satisfying the design goal System spatial resolution: 2.5 cm, dominated by multiple scattering expected from simulation σ: 109 ps σ: 2.5 cm pure muons p T : ~6 GeV/c position difference (cm)

59. 59 Ramona Vogt Workshop on Heavy Quark Production in Heavy-ion Collisions, Jan. 6, 2011, Purdue University

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