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HOT QUARKS 2006

Suppression of high-p T non-photonic electrons in Au+Au collisions at √s NN = 200 GeV. Jaroslav Bielcik Yale University/BNL. HOT QUARKS 2006. STAR. Hadron suppression in central AuAu. Hadron suppression in central AuAu.

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HOT QUARKS 2006

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  1. Suppression of high-pT non-photonic electrons in Au+Au collisions at √sNN = 200 GeV Jaroslav Bielcik Yale University/BNL HOT QUARKS 2006 jaroslav.bielcik@yale.edu

  2. STAR Hadron suppression in central AuAu Hadron suppression in central AuAu • Inclusive yields are strongly suppressed • in central Au+Au collisions at 200 GeV • Large energy loss of light quarks • in the formed nuclear matter Energy loss depends on properties of medium (gluon densities, size) depends on properties of “probe” (color charge, mass) Probing the medium with heavy quarks => need to measure heavy quark mesons p+p (d+Au) and Au+Au jaroslav.bielcik@yale.edu

  3. Measuring charm and beauty • Hadronic decay channels:D0Kp, D*D0p, D+/-Kpp (Haibin’s talk) • Non-photonic electrons: • Semileptonic channels: • c  e+ + anything(B.R.: 9.6%) • D0  e+ + anything(B.R.: 6.87%) • D e + anything(B.R.: 17.2%) • b  e+ + anything(B.R.: 10.9%) • B e + anything(B.R.: 10.2%) • Drell-Yan (small contribution for pT < 10 GeV/c) • Photonic electron background: • g conversions (p0 gg; g  e+e- ) • p0, h, h’ Dalitz decays • r, f … decays (small) • Ke3 decays (small) jaroslav.bielcik@yale.edu

  4. Heavy flavor electrons from FONLL heavy flavor e- from FONLL scaled to Cacciari, Nason, Vogt, Phys.Rev.Lett 95 (2005) • Beauty predicted to dominate above 4-5 GeV/c • Large uncertainty on b/c crossing point in • pT: from scales/masses variation it changes • from 3 to 9 GeV/c jaroslav.bielcik@yale.edu

  5. Energy loss of heavy quarks c, b 1) production in hard scattering 2) quark energy loss 3) fragmentation light ENERGY LOSS • Heavy quark has less dE/dx due to suppression of small angle gluon radiation “Dead Cone” effect Y. Dokshitzer & D. Kharzeev PLB 519(2001)199 Armesto, Salgado, Wiedemann, PRD 69 (2004) 114003 M.Djordjevic PRL 94 (2004) D, B (electrons) • D,B (electrons) spectra are affected by energy loss • Effect of collisional energy loss for heavy quarks • M.G.Mustafa Phys. Rev C 72 (2005) • M.Djordjevic nucl-th/0630066 jaroslav.bielcik@yale.edu

  6. hep-ph/0510284 0.4 0.3 0.2 0.1 Heavy quark energy loss BDMPS case BDMPS: Armesto, Salgado, Wiedemann, PRD 69 (2004) 114003 • Model: pQCD + E loss probability (quenching weights) + Glauber collision geometry light • Density ( ) “tuned” to match RAA in central Au-Au at 200 GeV Dainese, Loizides, Paic, EPJC 38 (2005) 461. =14 GeV2/fm RAA ~ 0.2light mesons RAA~ 0.4 for electrons from c+b heavy jaroslav.bielcik@yale.edu

  7. Djordjevic et al. Phys.Lett B 632, 81 (2006) Wicks et al nucl-th/0512076 Heavy quark energy loss DGLV case DGLV: Djordjevic, Guylassy Nucl.Phys. A 733, 265 (2004) + Elastic energy loss (Wicks et al nucl-th/0512076) dNg/dy=1000 gluon density of produced matter light RAA ~ 0.2light mesons RAA~ 0.4-0.6 for electrons from c+b heavy ignore the data for the moment jaroslav.bielcik@yale.edu

  8. HighTower trigger: • Only events with high tower ET>3 GeV/c2 • Enhancement of high pT STAR Detector and Data Sample • Electrons in STAR: • TPC: tracking, PID |h|<1.3 f=2p • BEMC (tower, SMD): PID 0<h<1 f=2p • TOF patch (Haibin talk) Preliminary results from: Run2003/2004 min. bias. 6.7M events with half field high tower trigger 2.6M events with full field (45% of all) 10% central 4.2M events (15% of all ) jaroslav.bielcik@yale.edu

  9. d K p p electrons electrons hadrons Electron ID in STAR – EMC • TPC: dE/dx for p > 1.5 GeV/c • Only primary tracks • (reduces effective radiation length) • Electrons can be discriminated well from hadrons up to 8 GeV/c • Allows to determine the remaining hadron contamination after EMC • EMC: • Tower E ⇒ p/E~1 for e- • Shower Max Detector • Hadrons/Electron shower develop different shape • Use # hits cuts • 85-90% purity of electrons • (pT dependent) • h discrimination power ~ 103-104

  10. M e+e-<0.14 GeV/c2 red likesign Photonic electrons background • Background:Mainly from g conv and p0,h Dalitz • Rejection strategy: For every electron candidate • Combinations with all TPC electron candidates • Me+e-<0.14 GeV/c2 flagged photonic • Correct for primary electrons misidentified as background • Correct for background rejectionefficiency ~50-60% for central AuAu Inclusive/Photonic: • Excess over photonic electrons observed for all system and centralities => non-photonic signal jaroslav.bielcik@yale.edu

  11. Beauty is expected to give an important contribution above5 GeV/c STAR non-photonic electron spectra pp, dAu, AuAu sNN = 200 GeV • pp, dAu: up to 10 GeV/c • AuAu: 0-5%, 10-40%, 40-80% up to 8 GeV/c • Photonic electrons subtracted • Corrected for 10-15% hadron contamination jaroslav.bielcik@yale.edu

  12. RAA nuclear modification factor Armesto et al. hep-th/0511257 van Hess et al. Phys. Rev. C 73, 034913 (2006) Wickset al. (DVGL) hep-th/0512076 Suppression up to ~ 0.5-0.6 observed in 40-80% centrality ~ 0.5 -0.6 in centrality 10-40% Strong suppression up to ~ 0.2 observed at high pTin 0-5% Maximum of suppression at pT ~ 5-6 GeV/c Theories currently do not describe the data well Only c contribution would be consistent with the RAA but not the p+p spectra jaroslav.bielcik@yale.edu

  13. RECENT ELECTRON RAA BY D. TEANEY • D.Teaney (Moriond 2006) • Input: spectrum of c+b from Cacciari et. al. • Weak coupling • Boltzmann-Langevin Model Phys.Rev.C71;064904 (2005) • Only collisional energy loss • Neglect radiative energy loss (gv<6) • Hadronization: according to measured fragmentation functions diffusion coefficient D=3/2pT corresponds to dNg/dy~2000 jaroslav.bielcik@yale.edu

  14. ^ • Large dNg/dy~ 3500, q ~14 GeV2/fm ? The low end of c-b overlap The high end of c-b overlap Armesto et al. hep-ph/0511257 Wicks et al nucl-th/0512076 Liu&Ko nucl-th/0603004 Large electrons suppression is a PUZZLE • Large suppression => large dE/dx of heavy quarks (NOT EXPECTED) Not enough, RAA saturates! • Where b starts to play a role? Maybe higher at pT? • Elastic energy loss? Important, helps, but not enough! • Recent study on 3 body cqq elastic scattering in QGP No beauty included! jaroslav.bielcik@yale.edu

  15. Summary • Non-photonic electrons from heavy flavor decays were measured in s = 200 GeV p+p, d+Au and Au+Au collisions by STAR up to pT~10 GeV/c Expected to have contribution from both charm and beauty • Strong suppression of non-photonic electrons has been observed in Au+Au, increasing with centrality Suggests large energy loss for heavy quarks ( RAA similar to light quarks ) • Theoretical attempts to explain it seem to fail if both b+c are included What is the contribution of b? Are there other/different contributions to energy loss? • It is desirable to separate contribution b+cexperimentally • detector upgrades (displaced vertex) • e-h correlations jaroslav.bielcik@yale.edu

  16. STAR Collaboration 545 Collaborators from 51 Institutions in 12 countries Argonne National Laboratory Institute of High Energy Physics - Beijing University of Bern University of Birmingham Brookhaven National Laboratory California Institute of Technology University of California, Berkeley University of California - Davis University of California - Los Angeles Carnegie Mellon University Creighton University Nuclear Physics Inst., Academy of Sciences Laboratory of High Energy Physics - Dubna Particle Physics Laboratory - Dubna University of Frankfurt Institute of Physics. Bhubaneswar Indian Institute of Technology. Mumbai Indiana University Cyclotron Facility Institut de Recherches Subatomiques de Strasbourg University of Jammu Kent State University Institute of Modern Physics. Lanzhou Lawrence Berkeley National Laboratory Massachusetts Institute of Technology Max-Planck-Institut fuer Physics Michigan State University Moscow Engineering Physics Institute City College of New York NIKHEF Ohio State University Panjab University Pennsylvania State University Institute of High Energy Physics - Protvino Purdue University Pusan University University of Rajasthan Rice University Instituto de Fisica da Universidade de Sao Paulo University of Science and Technology of China - USTC Shanghai Institue of Applied Physics - SINAP SUBATECH Texas A&M University University of Texas - Austin Tsinghua University Valparaiso University Variable Energy Cyclotron Centre. Kolkata Warsaw University of Technology University of Washington Wayne State University Institute of Particle Physics Yale University University of Zagreb jaroslav.bielcik@yale.edu

  17. electrons hadrons d K p p electrons electrons hadrons Electron ID in STAR – EMC • TPC: dE/dx for p > 1.5 GeV/c • Only primary tracks • (reduces effective radiation length) • Electrons can be discriminated well from hadrons up to 8 GeV/c • Allows to determine the remaining hadron contamination after EMC • EMC: • Tower E ⇒ p/E • Shower Max Detector (SMD) • Hadrons/Electron shower develop different shape • Use # hits cuts • 85-90% purity of electrons • (pT dependent) • h discrimination power ~ 103-104

  18. Charm Total Cross Section Charm total cross section per NN interaction 1.13  0.09(stat.)  0.42(sys.) mb in 200GeV minbias Au+Au collsions 1.4  0.2(stat.)  0.4(sys.) mb in 200GeV minbias d+Au collisions Charm total cross section follows roughly Nbin scaling from d+Au to Au+Au considering errors Indication of charm production in initial collisions jaroslav.bielcik@yale.edu

  19. What is v2? Non-central Au-Au collisions  azimuthally anisotropic source of matter in coordinate space  azimuthally anisotropic (isotropic) of particles in momentum space, given enough particle interactions  Non-zero (zero) v2 v2 is built up at the early stage of the collision so it is a nice probe of the hot and dense medium created at RHIC energy! jaroslav.bielcik@yale.edu

  20. Charm electron v2 determination OSLM: Opposite Sign Low Invariant Mass; SSLM: Same Sign Low Invariant Mass 1: inclusive 2: OSLM 3: SSLM 4: 2-3 5: 1-(2-3)/eff 1 2 3 4 5 AFTER SUBTRACTING BACKGOUND CONTRIBUTION – LARGE SYSTEMATIC ERRORS jaroslav.bielcik@yale.edu

  21. Electron v2 with new method – large systematic errors The detector material in STAR caused too much photonic background, which caused huge systematic and statistical uncertainties. Our result is not sensitive enough to make any conclusion about heavy quark v2 so far. jaroslav.bielcik@yale.edu

  22. Charm energy loss STAR Preliminary Strong suppression observed! Indicates charm energy loss in medium. For D0 RAA, stat. error only. jaroslav.bielcik@yale.edu

  23. Hadron contamination p/E method jaroslav.bielcik@yale.edu

  24. Electron reconstruction efficiency AuAu200GeV the central collisions determined from electron embedding in real events the data are corrected for this effect jaroslav.bielcik@yale.edu

  25. Part of the primary electrons is flaged as background AuAu200GeV the central collisions determined from electron embedding in real events the data are corrected for this effect jaroslav.bielcik@yale.edu

  26. Two fake conversion points reconstructed (picking one closer to primary vertex) jaroslav.bielcik@yale.edu

  27. Trigger bias MB/HT ratio (0-5%) jaroslav.bielcik@yale.edu

  28. Dalitz Decays: p0 ge+e-versus (p0,h)  ge+e- The background efficiency for Dalitz electrons is evaluated by weighting with the p0 distribution but should be weighted by the true p0+h distribution. Comparing the spectra of this both cases normalized to give the same integral for pT>1 GeV/c (cut-off for electron spectra) we see almost no deviation. The effect of under/over correction is on the few percent level! jaroslav.bielcik@yale.edu

  29. Electron/Hadron ratio jaroslav.bielcik@yale.edu

  30. jaroslav.bielcik@yale.edu

  31. P/E in momentum bins a.u. momentum [GeV/c] jaroslav.bielcik@yale.edu

  32. dEdx for pt bins jaroslav.bielcik@yale.edu

  33. 3 centrality bins: 0-5% 10-40% 40-80% Inclusive electron spectra AuAu sNN = 200 GeV • High tower trigger allows • STARtoextend electron • spectra up to 10 GeV/c • Corrected for hadron contamination ~10-15% jaroslav.bielcik@yale.edu

  34. STAR non-photonic electron spectra pp,dAu,AuAu sNN = 200 GeV • Photonic electrons subtracted • Excess over photonic electrons observed • Consistent with STAR TOF spectra Beauty is expected to give an important contribution above5 GeV/c jaroslav.bielcik@yale.edu

  35. RAA nuclear modification factor Suppression up to ~ 0.4-0.6 observed in 40-80% centrality ~ 0.3 -0.4 in centrality 10-40% Strong suppression up to ~ 0.2 observed at high pTin 0-5% Maximum of suppression at pT ~ 5-6 GeV/c jaroslav.bielcik@yale.edu

  36. TOF electrons STAR Preliminary Inclusive electron spectra sNN = 200 GeV • Excess of electrons over photonic background in all centralities and systems • Corrected for 10-15% hadron contamination jaroslav.bielcik@yale.edu

  37. STAR Preliminary STAR non-photonic electron spectra pp,dAu,AuAu sNN = 200 GeV • Photonic electrons subtracted • Consistent with STAR TOF spectra • Consistent with PHENIX Beauty is expected to give an important contribution above5 GeV/c jaroslav.bielcik@yale.edu

  38. jaroslav.bielcik@yale.edu

  39. Hadron suppression jaroslav.bielcik@yale.edu

  40. jaroslav.bielcik@yale.edu

  41. for the collaboration jaroslav.bielcik@yale.edu

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