Study of b quark contributions to non-photonic electron yields by azimuthal angular correlations between non-photonic electrons and hadrons Shingo Sakai for STAR collaboration Univ. of California, Los Angeles 1 Outline b/c separation in non-photonic electron at 200 GeV pp by electron-hadron (e-h & e-D 0 ) azimuthal STAR Discuss heavy flavor energy loss in the dense matter 2 Parton energy loss Gluon radiation model well represents R AA for neutral pion The model predicts that heavier quarks lose smaller energy due to dead cone effect The model predicts significant difference between bottom quark energy loss and light & charm quark energy loss. 3 Phys. Lett. B 632, 81 (2006) Heavy flavor energy loss Phys. Rev. Lett. 98 (2007) Heavy flavor production has been studied by measuring electrons decay from charm and bottom (non-photonic electron) at RHIC R AA for non-photonic electron is strong & consistent with hadrons Indicate a large energy loss for heavy quarks in the dense matter. Uncertainty from bottom quark contribution not only theory but also experiment 4 pQCD prediction for Bottom Since charm and bottom are heavy, their production have been predicted by pQCD FONLL predicts bottom quark contribution significant (c/b = 1) around 5 GeV/c in non-photonic electron yield with large uncertainty. Its important to experimentally determine bottom quark contribution to understand heavy flavor energy loss. *Uncertainty comes from mass, PDF, etc in the calculation *FONLL =A Fixed-Order plus Next- to-Leading-log 5 charm/bottom separation(1) Monte Carlo simulation (PYTHIA) for e D -h and e B -h Near side width for B decay is wider than that of D decay due to decay kinematics measuring e-h correlation in pp & fit by MC with B/(B+D) as parameter e D - h e B - h 6 Charm/bottom separation (2) e-D0 correlation Request like-sign e-K pair o near-side ; bottom dominant o away-side ; charm dominant 7 STAR Experiment Large acceptance Full azimuthal coverage => good for azimuthal correlation study TPC measure momentum measure dE/dx EMC + SMD measure energy measure shower shape => electron identification TOF measure Time of flight => particles (, K, p) identification 8 Particle Identification /K separation to 1.6 GeV/c 0.7 for TPC Alone ( +K)/p to p = 3 GeV/c 1.2 for TPC Alone electron Electron purity 98% for p T < 6 GeV/c 80% for 9 pp 9 TOF Photonic electron identification Photonic electron is main background Photonic electrons are experimentally reconstructed by calculating invariant mass at DCA for two electrons request mass < 0.1 # of reconstructed photonic e reconstruction efficiency ( reco ) is ~ 70% 10 a m (GeV/c 2 ) each distributions are experimentally determined. combinatorial 11 electron sample after removing opposite sign electron (inv. mass there would be bottom contribution in AuAu, too R AA for non-photonic electron consistent with hadrons Indicate large energy loss not only charm quark but also bottom quark. 15 C:B ~ pp R AA c & R AA b correlation (1) R AA C and R AA B are connected B decay pp With the measurements of pp and R AA, we can derive a relationship between R AA c and R AA b. 16 R AA c & R AA b correlation (2) o R AA c & R AA b correlation together with models o Dominant uncertainty is normalization in R AA analysis o R AA b < 1 ; B meson suppressed o prefer Dissociate and resonance model (large b energy loss) 17 I; Phys. Lett. B 632, 81 (2006) ; dN g /dy = 1000 II; Phys. Lett. B 694, 139 (2007) III; Phys.Rev.Lett.100(2008) STAR preliminary p T >5 GeV/c Summary Azimuthal correlation between non-photonic electron and hadron (e-h & e-D 0 ) has been measured at 200 GeV pp RHIC-STAR The azimuthal angular correlation differs for non-photonic electrons from D and B semi-leptonic decays We compare our measured azimuthal correlation with those from D and B semi-leptonic decays from PYTHIA p+p simulations to derive the relative ratio of B/(B+D) Our result indicates comparable B and D contributions to non-photonic electrons for p T GeV/c and it is consistent with FONLL calculation. Our measured B/D ratio would imply considerable b quark energy loss in medium based on R AA measurement from central Au+Au collisions 18