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Non-photonic electrons in Cu + Cu collisions at √ s NN = 200 GeV

Non-photonic electrons in Cu + Cu collisions at √ s NN = 200 GeV. A. G. Knospe Yale University For the STAR Collaboration 22 August 2008 Hot Quarks Conference Aspen Lodge, Estes Park, CO. Heavy Flavor and the QGP. light. 1. Heavy quarks produced in initial hard scattering of partons

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Non-photonic electrons in Cu + Cu collisions at √ s NN = 200 GeV

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  1. A. G. Knospe slide Non-photonic electrons in Cu + Cu collisions at √sNN = 200 GeV A. G. Knospe Yale University For the STAR Collaboration 22 August 2008 Hot Quarks Conference Aspen Lodge, Estes Park, CO

  2. A. G. Knospe slide Heavy Flavor and the QGP light 1 • 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 _ Parton Energy Loss bottom parton medium M.Djordjevic PRL 94 (2004)

  3. A. G. Knospe slide Heavy Flavor Decays 2 • Some studies reconstruct hadronic decays: i.e. D0Kp, D*D0p, D±Kpp, Ds±pf (S. Baumgart) non-photonic e± • 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 (crossover ~ 5 GeV/c) • Photonic e± background: • g conversions (p gg, g e+e-) • Dalitz decays of p0, h, h’ • r, f, Ke3 decays (small contributions)

  4. A. G. Knospe slide Heavy Flavor Decays 2 • Some studies reconstruct hadronic decays: i.e. D0Kp, D*D0p, D±Kpp, Ds±pf (S. Baumgart) non-photonic e± • 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 (crossover ~ 5 GeV/c) • Photonic e± background: • g conversions (p gg, g e+e-) • Dalitz decays of p0, h, h’ • r, f, Ke3 decays (small contributions) M. Cacciari et al., Phys. Rev. Lett.95 (2005) 122001

  5. A. G. Knospe slide Previous Results 3 To Remove Photonic e± Background: • Reconstruct g conversions and Dalitz decays: e-e+ pairs have low invariant mass • STAR cut: Minv < 150 MeV/c2 • Simulate background e± from “cocktail” of measured sources (g,p0,h, etc.) • Measure e± with converter, extrapolate to 0 rad. length 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 (2007) 172301 p+p

  6. A. G. Knospe slide Nuclear Modification Factor 4 • RAA for non-photonic e±: PHENIX consistent with STAR • Similar to light-hadron RAA at high pT • Kinematics: pT(e) < pT(D,B) • Use light-hadron RAA to constrain model parameters dNg/dy, q • Models tend to under-predict suppression • Heavy-Quark energy loss: • Gluon Radiation PHENIX and STAR: RAA for non-photonic e± central Au+Au, √sNN=200 GeV ^ Light-Hadron RAA PHENIX: PRL98 (2007) 172301 STAR: PRL98 (2007) 192301 DGLV: Djordjevic et al., Phys. Lett. B632 (2006) 81 BDMPS: Armesto et al., Phys. Lett. B637 (2006) 362

  7. A. G. Knospe slide Nuclear Modification Factor 4 • RAA for non-photonic e±: PHENIX consistent with STAR • Similar to light-hadron RAA at high pT • Kinematics: pT(e) < pT(D,B) • Use light-hadron RAA to constrain model parameters dNg/dy, q • Models tend to under-predict suppression • Heavy-Quark energy loss: • Gluon Radiation • Gluon Radiation + Elastic Collisions PHENIX and STAR: RAA for non-photonic e± central Au+Au, √sNN=200 GeV ^ Light-Hadron RAA PHENIX: PRL98 (2007) 172301 STAR: PRL98 (2007) 192301 DGLV: Wicks et al., Nucl. Phys. A784 (2007) 426-442 van Hees et al., Phys. Rev. C73 034913 (2006)

  8. A. G. Knospe slide Nuclear Modification Factor 4 • RAA for non-photonic e±: PHENIX consistent with STAR • Similar to light-hadron RAA at high pT • Kinematics: pT(e) < pT(D,B) • Use light-hadron RAA to constrain model parameters dNg/dy, q • Models tend to under-predict suppression • Heavy-Quark energy loss: • Gluon Radiation • Gluon Radiation + Elastic Collisions • Do only c decays contribute? PHENIX and STAR: RAA for non-photonic e± central Au+Au, √sNN=200 GeV ^ Light-Hadron RAA PHENIX: PRL98 (2007) 172301 STAR: PRL98 (2007) 192301 DGLV: Djordjevic et al., Phys. Lett. B632 (2006) 81 BDMPS: Armesto et al., Phys. Lett. B637 (2006) 362

  9. A. G. Knospe slide Nuclear Modification Factor 4 • RAA for non-photonic e±: PHENIX consistent with STAR • Similar to light-hadron RAA at high pT • Kinematics: pT(e) < pT(D,B) • Use light-hadron RAA to constrain model parameters dNg/dy, q • Models tend to under-predict suppression • Heavy-Quark energy loss: • Gluon Radiation • Gluon Radiation + Elastic Collisions • Do only c decays contribute? • Collisional Dissociation model PHENIX and STAR: RAA for non-photonic e± central Au+Au, √sNN=200 GeV ^ Light-Hadron RAA PHENIX: PRL98 (2007) 172301 STAR: PRL98 (2007) 192301 Collisional dissociation: Adil and Vitev, Phys. Lett. B649 (2007) 139

  10. A. G. Knospe slide Non-photonic electrons in Cu + Cu, 200 GeV events

  11. A. G. Knospe slide Cu + Cu Data Set 5 • Analyzed data from 2005 Cu + Cu 200 GeV run • High Tower Trigger • Barrel Electromagnetic Calorimeter (BEMC) tower with ETOW > 3.75 GeV • Enhances particle 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 • Analyzed 10M min. bias events and 1.9M high tower events

  12. A. G. Knospe slide Barrel Electromagnetic Calorimeter (BEMC): BEMC = Towers + Shower Maximum Detector (SMD) e± in STAR EMC: p/ETOW≈ 1 Use a loose cut: 0 < p/ETOW < 2 SMD used to identify e±: showers better developed than h± Require hits (≥ 2 strips) in both the h and f planes of SMD Time Projection Chamber (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 |h| < 0.7 quality cuts e± Identification 6 TPC energy loss vs. p EMC Bichsel: epKpd

  13. A. G. Knospe slide Barrel Electromagnetic Calorimeter (BEMC): BEMC = Towers + Shower Maximum Detector (SMD) e± in STAR EMC: p/ETOW≈ 1 Use a loose cut: 0 < p/ETOW < 2 SMD used to identify e±: showers better developed than h± Require hits (≥ 2 strips) in both the h and f planes of SMD Time Projection Chamber (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 |h| < 0.7 quality cuts e± Identification 6 p/ETOW vs. pT hadrons e±

  14. A. G. Knospe slide Barrel Electromagnetic Calorimeter (BEMC): BEMC = Towers + Shower Maximum Detector (SMD) e± in STAR EMC: p/ETOW≈ 1 Use a loose cut: 0 < p/ETOW < 2 SMD used to identify e±: showers better developed than h± Require hits (≥ 2 strips) in both the h and f planes of SMD Time Projection Chamber (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 |h| < 0.7 quality cuts e± Identification 6 SMD clusters sizes hadrons e±

  15. A. G. Knospe slide Corrections 7 • Embed simulated e± tracks into real Cu+Cu events • r = Reconstruction Efficiency:fraction of simulated e± reconstructed and identified by cuts • Correct for temporary losses in geometrical acceptance of BEMC • A = Mean Acceptance ≈ 78% • Correct for TPC energy loss and hadron contamination 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% Cu+Cu 200 GeV, MinBias, 0-54% from embedding 2 GeV/c < p < 3 GeV/c from real data p± e± h±

  16. A. G. Knospe slide Photonic e± Background 8 • Some ph. e± not rejected • Embed simulated p 0gg  e+e-decays + conversions into real Cu+Cu events • Also embed simulated p 0 Dalitz decays (p 0e+e-g) at 1.5% b.r. • 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ge+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: black: e+e- pairs blue: comb. back. red=photonic

  17. A. G. Knospe slide Results 9 • Apply corrections: • r: e± reconstruction efficiency • A: mean BEMC acceptance • aP: purity of e± sample • aE: dE/dx cut efficiency • eB: background rejection eff. • Trigger bias correction • Merge data sets • Nuclear Modification Factor: • Nbinary = 82.2 for 0-54% • For pT > 3 GeV/c:

  18. A. G. Knospe slide RAA Comparisons 10 • Consistent with p ±RAA in Cu+Cu 200 GeV • Consistent with Au+Au 200 GeV data for similar Npart 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

  19. A. G. Knospe slide Non-photonic e± are proxies for heavy quarks In Au + Au collisions: Suppression similar to light hadrons Models tend to under-predict suppression 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 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 Coming soon: Non-photonic e+ yields and RAA in three centrality bins Summary and Outlook 11 Thank you! Are there any questions?

  20. A. G. Knospe slide Additional Material

  21. A. G. Knospe slide B-decay Contribution • 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 Fractional Contribution of B X. Lin, SQM 2007

  22. A. G. Knospe slide Comparisons to PQCD • 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 • New PQCD calculations: • Error bars on total scc larger than earlier calculations • STAR data consistent with new upper limit (Prediction II) Total Charm Cross-Section Non-photonic e± in p+p, 200 GeV

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