QM2005 BudapestJaroslav Bielcik Motivation STAR and electron ID Analysis Results: p+p, d+Au, and...
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Transcript of QM2005 BudapestJaroslav Bielcik Motivation STAR and electron ID Analysis Results: p+p, d+Au, and...
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