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Light Vector Mesons and the Dielectron Continuum in PHENIX

Light Vector Mesons and the Dielectron Continuum in PHENIX. Sarah Campbell for the PHENIX Collaboration Resonance Workshop 2012 March 6, 2012 Austin, TX. Outline. Detector Light vector mesons Hadronic and dielectron decays HI and cold nuclear matter effects Dielectron Continuum

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Light Vector Mesons and the Dielectron Continuum in PHENIX

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  1. Light Vector Mesons and the Dielectron Continuum in PHENIX Sarah Campbell for the PHENIX Collaboration Resonance Workshop 2012 March 6, 2012 Austin, TX Resonance Workshop -- 3/7/2012

  2. Outline • Detector • Light vector mesons • Hadronic and dielectron decays • HI and cold nuclear matter effects • Dielectron Continuum • Generating a cocktail • Comparisons to cocktail and between data • Centrality and pT bins • Conclusions Resonance Workshop -- 3/7/2012

  3. e+ PHENIX • At RHIC • p+p, d+Au, Cu+Cu, Au+Au • Tracking • Good quality track in DCH, PC1 • pT /pT = 0.7%  1% pT • Electron ID • RICH ring & EMC shower • Particle ID • TOF dτ~ 100 ns • EMC dτ ~ 500 ns • Aerogel dτ~ 500 ns p e- Resonance Workshop -- 3/7/2012

  4. Light vector meson: Motivation • Light vector mesons: , , φ • Masses modified by medium? • LVM  e+ e- • E&M probe, no color charge • , φ Hadron decays •   ,   , φ K+K- Resonance Workshop -- 3/7/2012

  5. p+p Resonance Workshop -- 3/7/2012

  6. pT Spectra • →e+e- agree with →, → • ϕ→e+e- agree with ϕ→K+K- Resonance Workshop -- 3/7/2012

  7. Cold Nuclear Matter • No strong cold nuclear matter effects in , ϕ Resonance Workshop -- 3/7/2012

  8. ϕ modifications in HI • ϕ mass,  unchanged • ϕ suppression at high pT • RAA Cu+Cu and Au+Au agree Resonance Workshop -- 3/7/2012

  9. HI Modifications -- RAA • , ϕ are suppressed • ϕ, , KS at high pt like ,  • ϕlike K+, eHF at low pt; ϕnot like, at mid. pt • Baryon Meson difference in RAA Resonance Workshop -- 3/7/2012

  10. Dielectron Continuum: Motivation Possible modifications Chiral symmetry restoration Continuum enhancement Thermal radiation Modification of vector mesons •  e+ e- • Broad mass distribution • Short lifetime • Broadening (and/or mass shift) • EM probe, no color charge • Diverse Physics Signals • Direct virtual photons • Dalitz decays • Hadronic decays • Semi-leptonic heavy flavor • Vector mesons • Broadening/dropping mass • Full time evolution of QGP Suppression Suppression or Enhancement Thermal radiation Modified heavy flavor Resonance Workshop -- 3/7/2012

  11. Cocktail Generation • Hadrons from Exodus using data • Pion pT spectra fit • mT scaling: • When possible use measured mesons pT distributions • J/ψsuppression, J/ψ and ψ’ rad. tails • Charm, Bottom, Drell Yan from Pythia • In p+p, measure the σcc • agrees with non-photonic single e- σcc = 567 ± 57(stat) ± 193 (sys) μb • d+Au, Cu+Cu, Au+Au NColl scale • Filter into PHENX ideal acceptance • σcc = 544 ± 39(stat) ± 142(sys) ± 200 (model) μb Resonance Workshop -- 3/7/2012 A Adare PLB 670 313 (2009)

  12. γ e- e+ e+ π0 e+ e- π0 π0 γ e- γ e+ 0 e-  e+ e- Backgrounds Generate with event mixing • Combinatorial • Conversions • RICH Ring overlap • Double dalitz • Primarily , → • Like-, unlike-sign pairs at same rate • Jets • Like-, unlike-sign pairs at same rate Remove with cuts Simulate with Exodus-like code Simulate with Pythia Resonance Workshop -- 3/7/2012

  13. Component subtraction Use like-sign pairs to normalize BGs Subtract each of the BG components Like-sign acceptance corrected subtraction Correct the like-sign pairs to have the unlike-sign pair acceptance Subtract like-sign pairs from unlike-sign pairs In p+p, Au+Au, Cu+Cu both methods are consistent Background Removal – 2 Methods Resonance Workshop -- 3/7/2012

  14. p+p and d+Au Min Bias measurement Resonance Workshop -- 3/7/2012 PRC 81 02391 (2010)

  15. Au+Au Min Bias & Cu+Cu 0-10% measurement Resonance Workshop -- 3/7/2012 PRC 81 02391 (2010)

  16. Centrality Dependence NColl ordered Central Peripheral d+Au p+p Resonance Workshop -- 3/7/2012

  17. Compare p+p and d+Au • No cold nuclear matter effects Resonance Workshop -- 3/7/2012

  18. Most Central HI Spectra • 1/NPart scaled • Onset of LMR excess Resonance Workshop -- 3/7/2012

  19. Yields vs NPart Resonance Workshop -- 3/7/2012

  20. p+p in pT slices • Matches at low pT • High pT IMR excess • No bottom in cocktail • p+p non-photonic single electron pT not well described by PYTHIA • High pT LMR excess from thermal photons Resonance Workshop -- 3/7/2012

  21. Au+Au MB and Cu+Cu 0-10% in pT slices • LMR excess at low pT • High pT LMR excess from thermal photons Resonance Workshop -- 3/7/2012

  22. Thermal photons T=233+/-14+/-19 T=221+/-19+/-19 T=217+/-18+/-16 Resonance Workshop -- 3/7/2012

  23. LMR pT Spectra  TEff • Calculate local inverse slopes in m ranges (0 - 0.6), (0.6 – 2.5) • Soft component at m ~ 0.5 • TEff ~ 100 MeV • Over 50% of the excess Resonance Workshop -- 3/7/2012

  24. Conclusions • , ϕ • ϕ mass,  unmodified • Dielectron , ϕ decays agree with hadronic decays • No strong cold nuclear matter effects • ϕ RAA at low and intermediate pT • Baryon meson difference in RAA • Dielectrons • No cold nuclear matter effects • Thermal photons in p+p, d+Au, Cu+Cu, Au+Au at low mass, high pT • Soft enhancement in central Cu+Cu and Au+Au at low mass, low pT Resonance Workshop -- 3/7/2012

  25. If there was more time… PRD 83 052004 (2011) PRD 84 044902 (2011) • ϕin Cu+Cu •  in Cu+Cu • / ratios in p+p, d+Au, Cu+Cu, Au+Au • ϕ→K+K- in 62 GeV • ϕ→+- in the forward direction • KS→ , K*→K • More neutral mesons: →, →, →, ’→ • Talis fits to p+p pT spectra • Extract integrated yields • Temperature • mT scaling in p+p • Statistical model comparisons in p+p • Dielectron pT spectra in p+p Au+Au • Theory comparisons to Au+Au MB dielectrons • in mass, in mass in pT slices, in mT - m0 • High mass d+Au MB dielectron spectrum PRD 83 052004 (2011) PRC 81 034911 (2010) Resonance Workshop -- 3/7/2012

  26. Backup Resonance Workshop -- 3/7/2012

  27. Backup eta pi eta prime Resonance Workshop -- 3/7/2012

  28. Kaons Resonance Workshop -- 3/7/2012

  29. RAA Kaons Resonance Workshop -- 3/7/2012

  30. Backup – ϕ→KK two ways Resonance Workshop -- 3/7/2012

  31. RAA ϕ Resonance Workshop -- 3/7/2012

  32. RAA  Resonance Workshop -- 3/7/2012

  33. Pt fits in p+p Resonance Workshop -- 3/7/2012

  34. p+p pt spectra Resonance Workshop -- 3/7/2012

  35. Tallis distribution • Expo fails at higher pt • Failure points at different locations for different mesons  recombination • Parameters: • n, T and norm. • Extract int. yield Resonance Workshop -- 3/7/2012

  36. Resonance Workshop -- 3/7/2012

  37. Baryon Meson differences Resonance Workshop -- 3/7/2012

  38. Stat models Resonance Workshop -- 3/7/2012

  39. / ratios Resonance Workshop -- 3/7/2012

  40. Backup detector resolution Resonance Workshop -- 3/7/2012

  41. Backup pt Resonance Workshop -- 3/7/2012

  42. Is Pythia the right way to model the heavy quark components? • p+p non-photonic electron pT not well described by PYTHIA • Au+Au suppression of high pT non-photonic electrons • Model a random heavy quark component, using Au+Au non-photonic pT spectra with random angular orientation • Contains charm and bottom correlations Cocktail with Pythia Cocktail with Random Resonance Workshop -- 3/7/2012 A Adare et al PRL98 172301

  43. Combinatorial Background • Largest background in HI • Large multiplicities, combinatorial goes as multiplicity squared • Shape determined by event mixing Resonance Workshop -- 3/7/2012

  44. Require pairs are separated by twice the nominal ring size All Pairs Passing pairs Failing pairs Unlike-sign Like-sign All Pairs Passing pairs Failing pairs Beam pipe conversions Dalitz decay z z e- Conversion B Support structure B y y Air conversions x x e- e+ e+ Backgrounds ConversionsRing Overlap • Cut pairs with opening angle ┴ to B, low mass and charge ordered Resonance Workshop -- 3/7/2012

  45. γ e- e+ e+ π0 e+ e- π0 π0 γ e- γ e+ 0 e-  e+ e- Backgrounds Double DalitzJets • Decays with multiple e+e- • Like-, unlike-sign at same rate • Exodus-like simulation 0 e+e-e+e-,  0 0 0 • Pairs from 0 in jet correlated by jet • Like-, unlike-sign at same rate • Pythia simulation Simulated ,  Background All pairs Underlying evt Subtracted Near Away Unlike-sign Like-sign Resonance Workshop -- 3/7/2012 Like-sign

  46. Resonance Workshop -- 3/7/2012

  47. PHENIX vs STAR:Acceptance: low pt • PHENIX • +/- 0.5 rapidity • Single electrons pT >0.2 GeV • Pairs mT > 0.4 GeV • STAR efficiency at low pT? Resonance Workshop -- 3/7/2012

  48. PHENIX vs STAR p+p Resonance Workshop -- 3/7/2012

  49. PHENIX vs STAR Au+Au MB Resonance Workshop -- 3/7/2012

  50. p+p Normalization region Resonance Workshop -- 3/7/2012

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