Jaroslav BielcikQM2005 Budapest

Motivation STAR and electron ID Analysis Results: p+p, d+Au, and Au+Au at sNN = 200 GeV Summary

Centrality dependence of heavy flavor production from single

electron measurements

Centrality dependence of heavy flavor production from single

electron measurements

Jaroslav BielcikYale University/BNL

for the collaboration

Jaroslav Bielcik 2QM2005 Budapest

Heavy quark production at RHICHeavy quark production at RHIC

c, b

D, B

1)

production

2)

medium energy loss

3)

fragmentation

Heavy quark energy loss is expected

to be smaller because of dead cone

D,B spectra are affected by energy loss

Important test of transport properties of sQGP

Can we learn something from the difference between heavy and light quarks? How do heavy quarks interact with the medium?

– Thermalization, suppression?

light

(M.Djordjevic PRL 94 (2004))

ENERGY LOSS

Jaroslav Bielcik 3QM2005 Budapest

Detecting charm/beauty via semileptonic D/B decays

Detecting charm/beauty via semileptonic D/B decays

Hadronic decay channels: D0KD*D0D+/-K

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: conversions (0 ee) 0, ’ Dalitz decays , … decays (small) Ke3 decays (small)

See H.Zhang talk 5c

Jaroslav Bielcik 4QM2005 Budapest

Electrons and nuclear modification factor RElectrons and nuclear modification factor RAAAA

Beauty predicted to dominate above 4-5 GeV/c

Single e- from NLO/FONLL

prediction: electron suppression up to 2

scaled to

prediction: large electron suppression of ~ 5 for c onlymedium suppression of ~ 2.5 for c+b

M. Cacciari et al., hep-ph/0502203

Jaroslav Bielcik 5QM2005 Budapest

STAR Detector and Data SampleSTAR Detector and Data Sample

Electrons in STAR: TPC: tracking, PID ||<1.3 =2 BEMC (tower, SMD): PID 0<<1 =2 TOF patch

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 )

Processed:

HighTower trigger: Only events with high tower ET>3 GeV/c2

Enhancement of high pT

QM2005 Budapest

hadrons electrons

Electron ID in STAR – EMCElectron ID in STAR – EMC

1. 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

2. EMC: a) Tower E ⇒ p/Eb) 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

electrons

K p d

hadrons

electrons

Jaroslav Bielcik 7QM2005 Budapest

Electron backgroundElectron background

Inclusive electron spectra: Signal

– Heavy quarks semi-leptonic decays Dominant background− 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

Background rejection efficiency central Au+Au

M e+e-<0.14 GeV/c2

red likesign

Jaroslav Bielcik 8QM2005 Budapest

Inclusive electron spectra AuAu sNN = 200 GeV

Inclusive electron spectra AuAu sNN = 200 GeV

High tower trigger allows STAR to extend electron spectra up to 10 GeV/c

3 centrality bins: 0-5%

10-40%

40-80%

Corrected for hadron contamination ~10-15%

Remaining problem: charge exchange reaction in EMC at high pT: ± 0 (still under study)

Jaroslav Bielcik 9QM2005 Budapest

STAR non-photonic electron spectra pp,dAu,AuAu sNN = 200 GeV

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 above 5 GeV/c

See H.Zhang talk 5c

Jaroslav Bielcik 10QM2005 Budapest

pp

AA

AAAA

dpd

T

dpNd

R

3

3

3

3

RAA nuclear modification factorRAA 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 pT in 0-5%

Maximum of suppression at pT ~ 5-6 GeV/c

Jaroslav Bielcik 11QM2005 Budapest

SummarySummary 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 centralityRAA ~ 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 centrale-e correlation (what happens with the other D?)e-h correlation (heavy flavor tagged jets)

Jaroslav Bielcik 12QM2005 Budapest

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 PhysicsMichigan 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 UniversityPusan 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

545 Collaborators from 51 Institutionsin 12 countries

STAR CollaborationSTAR Collaboration