1 / 30

Suppression of high-p T non-photonic electrons in Au+Au collisions at √s NN = 200 GeV

Suppression of high-p T non-photonic electrons in Au+Au collisions at √s NN = 200 GeV. Jaroslav Bielcik Yale University/BNL. Why measure non-photonic electrons?. Non-photonic electrons indirect way to study heavy quarks. R AA. p+p – d+Au – Au+Au.

glen
Download Presentation

Suppression of high-p T non-photonic electrons in Au+Au collisions at √s NN = 200 GeV

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. Why measure non-photonic electrons? Non-photonic electrons indirect way to study heavy quarks RAA p+p – d+Au – Au+Au how heavy quarks interact with medium • 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%) Direct way: Hadronic decay channels: e.g. D0Kp jaroslav.bielcik@yale.edu

  3. Z. Lin & M. Gyulassy, PRC 51 (1995) 2177 Charm quark production • Charm is dominantly produced • in initial hard scattering • via gluon fusion: • Charm total cross-section should follow Nbin scaling from p+p to Au+Au STAR scc Observed binary scaling d+Au => Au+Au jaroslav.bielcik@yale.edu

  4. Heavy flavor electrons in FONLL heavy flavor e- from FONLL • FONLL: extension of NLO pQCD scaled to • Due to mass of heavy quarks it’s • production should be calculable in pQCD Cacciari, Nason, Vogt, Phys.Rev.Lett 95 (2005) • Beauty predicted to dominate above 4-5 GeV/c • Crossing point is important because of • huge c,b mass difference => • interactions can be different jaroslav.bielcik@yale.edu

  5. varying Uncertainty of c/b contribution • FONLL: • Large uncertainty on c/b crossing point in • pT: from scales/masses variation it changes • from 3 to 9 GeV/c jaroslav.bielcik@yale.edu

  6. Energy loss of quarks in medium Energy loss depends on properties of medium (gluon densities, size) depends on properties of “probe” (color charge, mass) nuclear modification factor: RAA= 1 … signal of medium effects RAA hadrons … light quarks and gluons RAA D,electrons … heavy quarks: c,b Charm and beauty quarks probe the nuclear matter in Au+Au jaroslav.bielcik@yale.edu

  7. Energy loss of heavy quarks 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) 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

  8. Density ( ) “tuned” to match RAA in central Au+Au at 200 GeV hep-ph/0510284 0.4 0.3 0.2 heavy 0.1 RAA~ 0.4 for electrons from c+b Heavy quark energy loss ASW case R.Baier, Yu.L.Dokshitzer, A.H.Mueller, S.Peigne' and D.Schiff, (BDMPS), Nucl. Phys. B483 (1997) 291. ASW: Armesto, Salgado, Wiedemann, PRD 69 (2004) 114003 light time averaged momentum transfer quark-medium per unit lenght Dainese, Loizides, Paic, EPJC 38 (2005) 461. =14 GeV2/fm RAA ~ 0.2light mesons jaroslav.bielcik@yale.edu

  9. heavy RAA~ 0.4-0.6 for electrons from c+b Heavy quark energy loss DVGL case DVGL: 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 jaroslav.bielcik@yale.edu

  10. HighTower trigger: • Only events with high tower ET>3 GeV/c2 • Enhancement of high pT STAR Detector • Electrons in STAR: • TPC: tracking, PID |h|<1.3 f=2p • BEMC (tower, SMD): PID 0<h<1 f=2p • TOF patch jaroslav.bielcik@yale.edu

  11. 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 • 85-90% purity of electrons • (pT dependent) • h discrimination power ~ 103-104 all p>1.5 GeV/c2 p/E SMD jaroslav.bielcik@yale.edu

  12. M e+e-<0.14 GeV/c2 red likesign • Excess over photonic electrons observed for all system and centralities => non-photonic signal 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 Au+Au Inclusive/Photonic: jaroslav.bielcik@yale.edu

  13. JB QM2005 nucl-ex/0511005 • Beauty is expected to give an important contribution above5 GeV/c STAR non-photonic electron spectra p+p, d+Au, Au+Au sNN = 200 GeV • p+p, d+Au: up to 10 GeV/c • Au+Au: 0-5%, 10-40%, 40-80% up to 8 GeV/c • Photonic electrons subtracted • Corrected for 10-15% hadron contamination jaroslav.bielcik@yale.edu

  14. STAR preliminary Electrons from p+p x FONLL pQCD sSTARcc/sFONLL 5.5 • FONLL has to be scaled by factor ~5.5 to match the data • Ratio Data/FONLL is constant ~ pT: both charm and beauty are needed to get shape • both charm and beauty are off in FONLL jaroslav.bielcik@yale.edu

  15. Electron 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 JB QM2005 nucl-ex/0511005 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

  16. 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 • FONLL underpredicts non-photonic electrons p+p electrons • 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? Collisional energy loss, multibody effects… • It is desirable to separate contribution b+cexperimentally • detector upgrades (displaced vertex) • e-h correlations jaroslav.bielcik@yale.edu

  17. 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

  18. STAR emc x tof x PHENIX jaroslav.bielcik@yale.edu

  19. electrons hadrons EMC electrons jaroslav.bielcik@yale.edu

  20. 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

  21. 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

  22. 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

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

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

  25. Hadron suppression jaroslav.bielcik@yale.edu

  26. jaroslav.bielcik@yale.edu

  27. R.Vogt Slides jaroslav.bielcik@yale.edu

  28. R.Vogt Slides jaroslav.bielcik@yale.edu

  29. R.Vogt Slides jaroslav.bielcik@yale.edu

  30. R.Vogt Slides jaroslav.bielcik@yale.edu

More Related