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Non-photonic electron production in STAR

Non-photonic electron production in STAR. A. G. Knospe Yale University 9 April 2008. slide 1. A. G. Knospe. light. Heavy Flavor and the QGP. Heavy quarks produced in initial hard scattering of partons Dominant: gg  QQ Production rates from pQCD

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Non-photonic electron production in STAR

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  1. Non-photonic electron production in STAR A. G. Knospe Yale University 9 April 2008

  2. slide 1 A. G. Knospe light Heavy Flavor and the QGP • Heavy quarks produced in initial hard scattering of partons • Dominant: gg  QQ • Production rates from pQCD • Sensitive to initial gluon distributions • Heavy quark energy loss • Prediction: less than light quark energy loss (dead cone effect) • Sensitive to gluon densities in medium _ ENERGY LOSS bottom parton medium M.Djordjevic PRL 94 (2004)

  3. slide 2 A. G. Knospe Heavy Flavor Decays • Must study heavy-flavor decay products • Some studies reconstruct hadronic decays: i.e. D0Kp, D*D0p, D±Kpp, Ds±pf (S. Baumgart, A. Shabetai) non-photonic e± • I look at semileptonic decay modes: • 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%) • m  decay modes • Heavy flavor decays expected to dominate non-photonic (single) e± spectrum; b decays should dominate at high pT • Photonic e± background: • g conversions (p gg, g e+e-) • Dalitz decays of p0, h, h’ • r, f, Ke3 decays (small contributions)

  4. slide 3 A. G. Knospe Previous Results To Remove Photonic e± Background: • Combine e± with oppositely charged tracks in same event; e± is background if Minv < 150 MeV/c2 • Simulate background e± from “cocktail” of measured sources (g,p0,h, etc.) • Measure e± with converter, extrapolate to 0 background STAR: Non-photonic e±, √sNN=200 GeV PHENIX: Non-photonic e±, √sNN=200 GeV Au+Au: 0-5% 10-40% Au+Au: 0-92% 40-80% 0-10% d+Au 10-20% 20-40% p+p 40-60% 60-92% STAR: B. I. Abelev et al, Phys. Rev. Lett. 98 (2007) 192301 PHENIX: A. Adare et al, Phys. Rev. Lett. 98, 172301 (2007) p+p

  5. slide 4 A. G. Knospe Nuclear Modification Factor • RAA for non-photonic e±: PHENIX consistent with STAR • Similar to light hadron RAA • Kinematics: pT(e±) < pT(D) • Use light hadron RAA to constrain parameters dNg/dy, q • Models tend to under-predict suppression • Models still being refined PHENIX and STAR: RAA for Non-photonic e± central Au+Au, √sNN=200 GeV ^ Light Hadron RAA PHENIX: PRL 98 (2007) 172301 STAR: PRL 98 (2007) 192301 DVGL: Djordjevic, Phys. Lett. B 632 (2006) 81 BDMPS: Armesto, Phys. Lett. B 637 (2006) 362

  6. slide 4 A. G. Knospe Nuclear Modification Factor • RAA for non-photonic e±: PHENIX consistent with STAR • Similar to light hadron RAA • Kinematics: pT(e±) < pT(D) • Use light hadron RAA to constrain parameters dNg/dy, q • Models tend to under-predict suppression • Models still being refined PHENIX and STAR: RAA for Non-photonic e± central Au+Au, √sNN=200 GeV ^ Light Hadron RAA PHENIX: PRL 98 (2007) 172301 STAR: PRL 98 (2007) 192301 DVGL: Wicks, nucl-th/0512076 (2005) van Hees, Phys. Rev. C 73 034913 (2006)

  7. slide 4 A. G. Knospe Nuclear Modification Factor • RAA for non-photonic e±: PHENIX consistent with STAR • Similar to light hadron RAA • Kinematics: pT(e±) < pT(D) • Use light hadron RAA to constrain parameters dNg/dy, q • Models tend to under-predict suppression • Models still being refined • Do only c decays contribute? PHENIX and STAR: RAA for Non-photonic e± central Au+Au, √sNN=200 GeV ^ Light Hadron RAA PHENIX: PRL 98 (2007) 172301 STAR: PRL 98 (2007) 192301 DVGL: Djordjevic, Phys. Lett. B 632 (2006) 81

  8. slide 5 A. G. Knospe B-decay Contribution Fractional Contribution of B • STAR measures angular correlations of non-photonic e+ with hadrons • sensitive to relative contributions of D and B decays • Measured B/(B+D) ratio consistent with FONLL • ~ 40% at pT=5 GeV/c • b-quarks should be considered in RAA calculation (cf. previous slide) X. Lin, SQM 2007

  9. Non-photonic electrons in Cu + Cu, 200 GeV events

  10. Analyze STAR data from 2005 Cu+Cu 200 GeV run EMC High Tower Trigger: At least one tower with E > 3.75 GeV Enhances yields at high pT Start with: 34M minimum bias events and 3.7M high tower events Event Selection Cuts: centrality 0-54% primary vertex |z| < 20 cm Normal e+ yield Analyzed 10M min. bias events and 1.9M high tower events slide 6 A. G. Knospe Cu+Cu: Event Selection preliminary preliminary

  11. BEMC: EMC = Towers + Shower Maximum Detector (SMD) e± in STAR EMC: p/E≈ 1 Use a loose cut: 0 < p/E < 2 SMD used to identify e±: showers better developed than h± Require hits (> 2 strips) in both the h and f planes of SMD Mean BEMC Acceptance ~78% TPC: 3.5 < dE/dx < 5 keV/cm Good dE/dx separation between e± and p ± for p > 1.5 GeV/c distance to primary vertex < 1.5 cm 0 < h < 0.7 quality cuts slide 7 A. G. Knospe e± Identification EMC preliminary

  12. BEMC: EMC = Towers + Shower Maximum Detector (SMD) e± in STAR EMC: p/E≈ 1 Use a loose cut: 0 < p/E < 2 SMD used to identify e±: showers better developed than h± Require hits (> 2 strips) in both the h and f planes of SMD Mean BEMC Acceptance ~78% TPC: 3.5 < dE/dx < 5 keV/cm Good dE/dx separation between e± and p ± for p > 1.5 GeV/c distance to primary vertex < 1.5 cm 0 < h < 0.7 quality cuts slide 7 A. G. Knospe e± Identification hadrons e± preliminary preliminary

  13. BEMC: EMC = Towers + Shower Maximum Detector (SMD) e± in STAR EMC: p/E≈ 1 Use a loose cut: 0 < p/E < 2 SMD used to identify e±: showers better developed than h± Require hits (> 2 strips) in both the h and f planes of SMD Mean BEMC Acceptance ~78% TPC: 3.5 < dE/dx < 5 keV/cm Good dE/dx separation between e± and p ± for p > 1.5 GeV/c distance to primary vertex < 1.5 cm 0 < h < 0.7 quality cuts slide 7 A. G. Knospe e± Identification SMD Clusters: hadrons e± preliminary preliminary

  14. slide 8 A. G. Knospe Corrections Cu+Cu 200 GeV, MinBias, 0-54% • Embed simulated e± tracks into real Cu+Cu events • r = Reconstruction Efficiency:fraction of simulated e± reconstructed and identified by cuts • Correct for TPC energy loss separately • Fit ln(dE/dx) projections in p slices • purity (aP):fraction of particles within dE/dx cut that are e± • 90-100%, decreasing w/ pT • efficiency (aE):fraction of e± that fall within dE/dx cut • 70-80% from embedding preliminary 2 GeV/c < p < 3 GeV/c from real data p± e± preliminary h±

  15. slide 9 A. G. Knospe Photonic e± Background • Some ph. e± not rejected • Embed simulated p 0gg  e+e-decays + conversions into real Cu+Cu events • Background rejection efficiency (eB): eff. to find true conversion partner (70-80%) • Dominant sources of photonic e±: • Conversion (ge+e-) • Dalitz decays (p0,he+e-) • Photonic e± from invariant mass cut: • e± is paired with oppositely-charged tracks in same event • Same-charge pairs give combinatorial background • Find pairs with dca < 1.5cm and M(e+e-) < 150 MeV/c2 • Photonic e± yield: 1.2 GeV/c < pT < 1.6 GeV/c preliminary black: e+e- pairs blue: comb. back. red=photonic invariant mass [GeV/c2]

  16. slide 10 A. G. Knospe Spectra and RAA • Apply corrections: • Merge data sets • Nuclear Modification Factor: • Nbinary = 82.2 for 0-54% • RAA ~ 0.6 - 0.7 for pT > 3 GeV/c preliminary preliminary

  17. slide 11 A. G. Knospe RAA Comparisons • Consistent with Au+Au 200 GeV data for similar Npart • Consistent with p ±RAA in Cu+Cu 200 GeV RAA for non-photonic e± RAA for p ±, Cu+Cu 200 GeV Non-photonic e± Cu+Cu 200 GeV 0-54% * R. Hollis, WWND 2007 STAR: PRL 98 (2007) 192301 PHENIX: PRL 98 (2007) 172301

  18. Non-photonic e± are proxies for heavy quarks Found the non-photonic e± spectra in Cu+Cu 200 GeV data Particle ID in TPC, BEMC, BSMD Remove photonic e± with invariant mass cut: M(e+e-) < 150MeV/c2 Nuclear Modification Factor 0.6 - 0.7 for pT > 3 GeV/c, centrality 0-54% Consistent with p ±RAA in Cu+Cu 200 GeV Consistent with non-photonic e±RAA in Au+Au 200 GeV at similar Npart slide 12 A. G. Knospe Summary

  19. Coming soon: find yields and RAA in three centrality bins Paper on D-mesons and non-photonic e± in Cu+Cu 200 GeV: S. Baumgart, A. G. Knospe, and A. Shabetai slide 13 A. G. Knospe The Future Thank you! Are there any questions?

  20. Additional Material

  21. A. G. Knospe Comparisons to PQCD • New PQCD calculations: • Error bars on total scc larger than earlier calculations • STAR data consistent with new upper limit (Prediction II) • FONLL describes shape of non-photonic e± spectra • PHENIX spectrum < STAR by factor ~2 • FONLL predition < STAR by factor ~4-5 • differences constant in pT Total Charm Cross-Section Non-photonic e± in p+p, 200 GeV

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