Xiaoyan LinHard Probes 2006, Asilomar, June Azimuthal correlations between non-photonic electrons and charged hadrons in p+p collisions from STAR Xiaoyan Lin IOPP/UCLA For the STAR Collaboration  Motivation  Electron identification  Photonic electron background  Electron-hadron correlation  Comparison to PYTHIA  Summary

Xiaoyan LinHard Probes 2006, Asilomar, June STAR Features in H-Q Measurements at RHIC Heavy Quark R AA = Light Quark R AA Curves: S. Wicks, et al, nucl-th/

Xiaoyan LinHard Probes 2006, Asilomar, June Features in H-Q Measurements at RHIC Heavy Meson Flows ! Note the decay kinematics of D and B mesons are different! Electrons from B decays cannot follow the B meson momentum direction as good as electrons from D decays! Non-photonic electron V 2 Curves: Greco, Ko, Rapp, PLB 595 (2004) 202

Xiaoyan LinHard Probes 2006, Asilomar, June Charm versus b quark contribution Quantitative understanding of features in heavy quark measurements requires Charm versus b quark contributions to non-photonic electrons ! Such information should be best obtained from direct measurement of hadronic decays of charm and bottom mesons. This motivates the STAR and PHENIX vertex detector upgrade! See Dr. Nu Xu’s talk. Non-photonic electron and hadron correlations can help to estimate the C and B contribution ! X. Lin hep-ph/

Xiaoyan LinHard Probes 2006, Asilomar, June Significant difference between D decays and B decays in the near-side correlations. The difference is largely due to decay kinematics, not the production dynamics. The large difference in the near-side Δφ between D and B mesons can help us to estimate relative B and D contributions to non-photonic electrons. PYTHIA Simulation 2.5<P T (trig)<3.5 GeV/c3.5<P T (trig)<4.5 GeV/c4.5<P T (trig)<5.5 GeV/c Associated P T > 0.1 GeV/c

Xiaoyan LinHard Probes 2006, Asilomar, June Signal: Non-photonic electron Background: Hadron Photonic electron Major Detectors Used Time Projection Chamber (TPC) Electro-Magnetic Calorimeter (EMC) Shower Maximum Detector (SMD) Charm decay Bottom decay Photon conversion π 0 Dalitz decay η Dalitz decay kaon decay vector meson decays Data Sample:  s NN = 200 GeV in year 5 run. About 20M p+p collisions at  s NN = 200 GeV in year 5 run.

Xiaoyan LinHard Probes 2006, Asilomar, June Electron Identification: dE/dx TPC can identify charged particles to some extent Two orders of magnitude more hadrons than electrons Additional information needed to identify electrons (-0.4σ, 3.0σ)

Xiaoyan LinHard Probes 2006, Asilomar, June Electron Identification: P/E P is measured by TPC. E is the sum of the associated BEMC points’ energy measured by BEMC. Electrons will deposit almost all of their energy in the BEMC towers. 0.3 < P/E <1.5 was used to keep electrons and reject hadrons.

Xiaoyan LinHard Probes 2006, Asilomar, June Electron Identification: Shower Size Number of SMD hits per shower indicates shower size. Electrons have larger number of BSMD hits than those for hadrons. Electron candidates have to satisfy Number of BSMD hits > 1.

Xiaoyan LinHard Probes 2006, Asilomar, June Electron Identification: Projection Distance -3σ < ZDist < 3σ and -3σ < PhiDist < 3σ were set to remove lots of random associations between TPC tracks and BEMC points.

Xiaoyan LinHard Probes 2006, Asilomar, June Purity of Inclusive Electron Sample electron p T purity GeV/c99.99% GeV/c99.34% GeV/c99.14%

Xiaoyan LinHard Probes 2006, Asilomar, June Photonic Background The combinatorial background is small. Reconstructed photonic electron is the subtraction. Photonic electron is the reconstructed-photonic/eff eff ~ 60-70% from simulation for pp year 4. Still working on progress for pp year 5. M<100 MeV/c 2

Xiaoyan LinHard Probes 2006, Asilomar, June Method to Extract the Signal of E-H Correlation Start with Semi-Inclusive electron sample. If tracks pass the electron identification cuts, then they are inclusive electrons. In this inclusive electron sample we throw away those electrons which satisfy the photon conversion condition. The sample remaining is called semi-inclusive electrons. Semi-Inclusive = non-phtonic + not reconstructed-photonic - combinatorics Combinatorics can be estimated by Same-Sign. Not reco-photonic = photonic – reco-photonic = (1/eff – 1) (reco-photonic). For the e-h correlation analysis, we have to remove the photonic partner of the reco-photonic. Δφ non-pho = Δφ semi-inc + Δφ combinatorics - (1/ε -1) (Δφ opp-sign- NoPartner - Δφ same-sign-NoPartner )

Xiaoyan LinHard Probes 2006, Asilomar, June Δφ Distributions 2.5<P T (trig)<3.5 GeV/c3.5<P T (trig)<4.5 GeV/c4.5<P T (trig)<5.5 GeV/c Associated P T > 0.1 GeV/c Semi-inc Combinatorics

Xiaoyan LinHard Probes 2006, Asilomar, June Δφ Distributions 2.5<P T (trig)<3.5 GeV/c3.5<P T (trig)<4.5 GeV/c4.5<P T (trig)<5.5 GeV/c Opposite-Sign Same-Sign

Xiaoyan LinHard Probes 2006, Asilomar, June Comparison to PYTHIA Simulation Assume the photonic b.g. reconstruction efficiency is 70% At low p T GeV/c, the preliminary data indicates D contribution is dominate.

Xiaoyan LinHard Probes 2006, Asilomar, June Comparison to PYTHIA Simulation Assume the photonic b.g. reconstruction efficiency is 70% At high p T GeV/c, the preliminary data indicates D contribution is larger than B.

Xiaoyan LinHard Probes 2006, Asilomar, June Summary  We find that non-photonic electron and hadron correlations are sensitive to D and B contributions.  The preliminary data indicates D contribution is larger than B contribution up to P T ~ 5.5 GeV/c.  To quantitatively estimate B contribution, we need more study on the background, photonic electron reconstruction efficiency…

Xiaoyan LinHard Probes 2006, Asilomar, June Back up slides

Xiaoyan LinHard Probes 2006, Asilomar, June Photonic b.g. reco. efficiency uncertainty

Xiaoyan LinHard Probes 2006, Asilomar, June Photonic b.g. reco. efficiency uncertainty

Xiaoyan LinHard Probes 2006, Asilomar, June Photonic b.g. reco. efficiency uncertainty

Xiaoyan LinHard Probes 2006, Asilomar, June Width of near-side peak in PYTHIA simulation electron Pt (GeV/c) All hadrons e from D decays ± ± ± Hadrons from D decays e from D decays ± ± ±

Xiaoyan LinHard Probes 2006, Asilomar, June