Centrality dependence of heavy flavor production from single electron measurements

1. for the collaboration Centrality dependence of heavy flavor production from single electron measurements Jaroslav Bielcik Yale University/BNL • Motivation • STAR and electron ID • Analysis • Results: p+p, d+Au, and Au+Au at sNN = 200 GeV • Summary Jaroslav Bielcik

2. Heavy quark production at RHIC light ENERGY LOSS D, B c, b 1) production 2) medium energy loss 3) fragmentation (M.DjordjevicPRL 94 (2004)) • Can we learn something from the difference between heavy and light quarks? • How do heavy quarks interact with the medium? • Thermalization, suppression? • Important test of transport properties of sQGP • Heavy quark energy loss is expected to be smaller because of dead cone • D,B spectra are affected by energy loss Jaroslav Bielcik

3. Detecting charm/beauty via semileptonic D/B decays • Hadronic decay channels:D0Kp, D*D0p, D+/-Kpp • 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) See H.Zhang talk 5c Jaroslav Bielcik

4. Electrons and nuclear modification factor RAA Single e- from NLO/FONLL scaled to M. Cacciari et al., hep-ph/0502203 prediction: electron suppression up to 2 • Beauty predicted to dominate above 4-5 GeV/c prediction: large electron suppression of ~ 5 for c only medium suppression of ~ 2.5 for c+b Jaroslav Bielcik

5. 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 Processed: 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

6. 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 ~ 104-105

7. M e+e-<0.14 GeV/c2 red likesign Background rejection efficiency central Au+Au Electron background • Inclusive electron spectra: Signal • Heavy quarks semi-leptonic decays Dominantbackground • Instrumental: • γ conversion • Hadronic decays: - Dalitz decays (π0, η) • 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 rejection efficiency Jaroslav Bielcik

8. 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% • Remaining problem: charge exchange reaction in EMC at high pT: p± p0 gg (still under study) Jaroslav Bielcik

9. STAR non-photonic electron spectra pp,dAu,AuAu sNN = 200 GeV • Photonic electrons subtracted • Excess over photonic electrons observed • Consistent with STAR TOF spectra See H.Zhang talk 5c Beauty is expected to give an important contribution above5 GeV/c Jaroslav Bielcik

10. 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

11. 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~10GeV/c • Strong suppression of non-photonic electrons has been observed in Au+Au increasing with centrality • RAA ~ 0.2-0.3 for pT> 3 GeV/c • suggests large energy loss of heavy quarks • Need more detailed theory (incl. b suppression and centrality dependence) • Still more data on tape … • More stat at central • e-e correlation (what happens with the other D?) • e-h correlation (heavy flavor tagged jets) Jaroslav Bielcik

12. 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