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Photons and Dileptons

This presentation by K. Dusling and I. Zahed outlines advances in understanding photon and dilepton production rates in heavy-ion collisions, emphasizing the role of acceptance evolution and hadronic rates. The talk covers critical elements including resonance gases, chiral restoration, and the evolution of emitted particles in a quark-gluon plasma (QGP). Highlighting experimental comparisons between NA60 and PHENIX, it discusses the implications of thermal and chemical freeze-out processes on the observable signatures within the QGP context.

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Photons and Dileptons

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  1. Photons and Dileptons K. Dusling (NC) and I. Zahed BNL 11

  2. Outline • Set up • Rates • Evolution • Experiments

  3. AACartoon time

  4. Formally acceptance evolution rate

  5. Acceptance: NA60 vs PHENIX

  6. Hadronic Rates

  7. Rate l+ l+ l- l- π π π π N N

  8. Resonance Gas: 0 ie J=ρ,ρ’,ρ’’,.. +2+3, …-Pi, +2+3, …-K +2+3, …-N Hadronic Expansion

  9. + … + … Many Feyman Graphs: + … +

  10. Chiral Ward Identities: κ κ Chiral Limit and zero-mtm pion:

  11. VA Mixing=LxR Restoration? ~κ Dey, Eletsky, Ioffe 96

  12. Expansion Parameter: LXR  = 0 “Dilute”

  13. Chiral Ward Identities: κ^2

  14. Input:  e+e-   Decay .

  15. VA Mixing in T=180 MeV

  16. a1a1 Typical Mixing in T=150 MeVμb=225 MeV

  17. VA Mixing + Bremsstralung

  18. QGP Rates

  19. wQGP: l+ l+ l- l-

  20. wQGP: γ Collinear Enhancement+ LPM Effect : Arnold, Moore, Yaffe 01

  21. Hydro Evolution

  22. Fireball: NA60

  23. Thermal Freeze-out Cooper-Frye

  24. Chemical Freezeout: Fireball cools faster x Rates higher = w/μπ !

  25. Experiments

  26. NA60:

  27. PHENIX: Dusling+Z 07 Dusling+Z 09

  28. STAR: 11’ PHENIX PRC 81 (2010) 034911 Enhancement factor in 0.15<Mee<0.75 Gev/c2 Note: Acceptance difference etc. 28

  29. WA98: γ 0<qT (GeV) <4 0<qT (GeV)<0.8 N:x2

  30. Rates at RHIC: γ RHIC1 RHIC2

  31. PHENIX: γ RHIC1 RHIC2

  32. PHENIX extrapolation: γ PHENIX: M<<qv 1

  33. Systematics of the Extrapolation 15% Systematics!

  34. LHC: γ 0<qT(GeV)<2 1<qT (GeV)<5

  35. Achievements • EM “OK”* • LxR “restored” • QGP “visible” (*PHENIX)

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