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Theory Update on Electromagnetic Probes II

Theory Update on Electromagnetic Probes II. Ralf Rapp Cyclotron Institute + Physics Department Texas A&M University College Station, USA CATHIE/TECHQM Workshop BNL (Upton, NY), 16.12.09. 1.) Intro: Probing Strongly Interacting Matter. Electromagnetic Probes:

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Theory Update on Electromagnetic Probes II

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  1. Theory Update on Electromagnetic Probes II Ralf Rapp Cyclotron Institute + Physics Department Texas A&M University College Station, USA CATHIE/TECHQM Workshop BNL (Upton, NY), 16.12.09

  2. 1.) Intro:Probing Strongly Interacting Matter • Electromagnetic Probes: • penetrating:lEM >> Rnuc • Equilibrium: • EM spectral function • Im PEM(q0,q;mB,T) • Information via EM Spectral Function: • degrees of freedom (parton vs. hadron) • transport properties (EM conductivity, susceptibility) • relation to order parameters (chiral symmetry) • measure of temperature

  3. Outline 1.) Introduction 2.) EM Emission + Vector Mesons  Thermal Rate and Conductivity  Chiral Symmetry Breaking  r and a1 Meson in Medium 3.) Dilepton Spectra in A-A  Thermal Emission at SPS  The RHIC Problem 4.) Conclusions

  4. e+ e- γ 2.1 Thermal Electromagnetic Emission EM Current-Current Correlation Function: Thermal Dilepton and Photon Production Rates: Im Πem(M,q) Im Πem(q0=q) r-meson dominated Low Mass: ImPem~ [ImDr + ImDw /10 + ImDf /5]

  5. 2.2 Electric Conductivity • pion gas (chiral pert. theory) • sem / T ~ 0.01 for T ~ 150-200 MeV [Fernandez-Fraile+Gomez-Nicola ’07] • quenched lattice QCD • sem / T ~ 0.35 for T = (1.5-3) Tc [Gupta ’04] • soft-photon limit

  6. 2.3 Chiral Symmetry Breaking + Hadron Spectrum Condensates fill QCD vacuum: Axial-/Vector Correlators Constituent Quark Mass “Data”: lattice [Bowman et al ‘02] Theory: Instanton Model [Diakonov+Petrov; Shuryak ‘85] pQCD cont. • Weinberg Sum Rule(s) • chiral breaking:|q2| ≤ 1 GeV2 • Gellmann-Oakes-Renner: • mp2 fp2 = mq‹0|qq|0› -

  7. 2.4 r-Meson in Medium: Hadronic Interactions > rB /r0 0 0.1 0.7 2.6 > rMeson “Melting” Switch off Baryons [RR,Wambach et al ’99] [Chanfray et al, Herrmann et al, RR et al, Koch et al, Klingl et al, Mosel et al, Eletsky et al, Ruppert et al, Sasaki et al …] Dr (M,q;mB ,T) = [M 2 - mr2 -Srpp -SrB -SrM ] -1 r-Propagator: B*,a1,K1... r Sp r SrB,rM= Selfenergies: Srpp= N,p,K… Sp Constraints:decays:B,M→ rN, rp, ... ; scattering:pN→rN, gA, …

  8. 2.4.2 r Meson in Cold Nuclear Matter: JLab Nuclear Photo-Production: r e+ e- g + A → e+e- X Eg=1.5-3GeV g [CLAS/JLab ‘08] Theoretical Approach: [Riek et al ’08] in-medium r spectral function elementary production amplitude + Fe-Ti r g N M[GeV] Mee[GeV]

  9. p Sp Sp Sp r Sr Sr Sr 2.6 Axialvector in Medium: Dynamical a1(1260) p a1 resonance + + . . . = Vacuum: r In Medium: + + . . . • in-medium p + r propagators • broadening of p-r scattering • amplitude [Cabrera,Jido,Roca+RR ’09]

  10. e+ e- q q _ Thermal Sources:Relevance: - Quark-Gluon Plasma: high mass + temp. qq → e+e-, …M >1.5GeV, T >Tc - Hot + Dense Hadron Gas: M ≤ 1 GeV p+p- → e+e-, … T ≤ Tc - e+ e- p- p+ r(770) 3.) Dilepton Spectra in A-A Thermal Dilepton Emission Rate: e+ e- g* Im Πem(M,q;mB,T) Im Πem ~ Im Dr

  11. - [qq→ee] [HTL] 3.1 Dilepton Rates: Hadronic vs. QGPdRee /dM2 ~ ∫d3q f B(q0;T) ImPem • Hard-Thermal-Loop [Braaten et al ’90] • enhanced over Born rate • Hadronic and QGP rates • “degenerate” around~Tc • Quark-Hadron Duality at all M?! • ( degenerate axialvector SF!)

  12. 3.2 Dilepton “Excess” Spectra at SPS Thermal Emission Spectrum: • “average” Gr (T~150MeV) ~ 350-400 MeV • Gr (T~Tc) ≈ 600 MeV → mr • fireball lifetime: tFB ~ (6.5±1) fm/c [van Hees+RR ‘06, Dusling et al ’06, Ruppert et al ’07, Bratkovskaya et al ‘08]

  13. 3.2.2 NA60 Data vs. In-Medium Dimuon Rates Mmm [GeV] [van Hees +RR ’07] [RR,Wambach et al ’99] • acceptance-corrected data directly reflect thermal rates!

  14. 3.2.3 NA60 Excess Spectra vs. Theory [CERN Courier Nov. 2009] • Thermal source does very well • Low-mass enhancement very sensitive to medium effects • Intermediate-mass: total agrees, decomposition varies

  15. Intermediate Mass Region 3.2.4 NA60 Dimuons: Sensitivity to QGP and Tc • vary critical and chemical-freezeout temperature (Tfo ~ 130 MeV fix) “EoS-B” “EoS-C” • spectral shape robust: “duality” of dilepton rate around “Tc”! • intermediate mass (M>1GeV): QGP vs. hadronic depends on Tc

  16. 3.2.5 EM Probes in Central Pb-Au/Pb at SPS Di-Electrons [CERES/NA45] Photons [WA98] [Turbide et al ’03, van Hees+RR ‘07] • consistency of virtual+real photons (same Pem) • very low-mass di-electrons ↔ (low-energy) photons [Srivastava et al ’05, Liu+RR ‘06]

  17. 3.3 Low-Mass Dileptons at RHIC: PHENIX Inclusive Mass Spectrum Centrality Dependence of Excess • Successful approach at SPSfails at RHIC • Excess concentrated: - at low mass • - in central collisions • - at low pt (Teff ~ 100 MeV)

  18. Disoriented Chiral Condensate (DCC)? [Z.Huang+X.N.Wang ‘96] - “baked Alaska” ↔ small T - rapid quench+large domains ↔ central A-A - ptherm + pDCC → e+ e- ↔ M~0.3GeV, small pt [Bjorken et al ’93, Rajagopal+Wilczek ’93] 3.3.2 Origin of the Low-Mass Excess in PHENIX? • Soft QGP Radiation? - small Teff slope - why not in semi-central? - generic space-time argument:  maximal emission aroundTmax ≈ M / 5.5 (forImPem =const) Low mass (M<1GeV): Tmax < 200MeV

  19. 3.3.3 Low-Mass Excess from DCC? Dileptons from a DCC-DCC annihilation [Witham+RR ‘08] • too small • DCC-thermal to be evaluated …

  20. 3.3.4 Comparison of Thermal Emission Calculations Chiral Reduction + Hydro Hadronic Many-Body + Fireball • Decomposition at M=0.5(0.2)GeV: Hadronic LO-QGP NLO-QGP • Dusling+Zahed 6 (6) 5.5 (2) 10 (25) • RR+van Hees 20 (15) 4 (3) --

  21. 4.) Conclusions • Electromagnetic Probes • - versatile tool (spectral fcts., transport, temp., lifetime!) • Chiral Symmetry Breaking (Restoration) • - chiral partners: r - a1 (degeneracy at Tc) • Thermal Dilepton Rates • - melting r toward Tc : quark-hadron duality?! • hadron liquid?! • Dilepton Spectra • - quantitative agreement at SPS • - failure at RHIC thus far (QGP not favored; DCC??)

  22. 2.3.2 Acceptance-Corrected NA60 Spectra Mmm [GeV] Mmm [GeV] • more involved at pT>1.5GeV: Drell-Yan, primordial/freezeout r , …

  23. X.) Example for Comprehensive Analysis: NA60 Dileptons Charmonium Flow Charmonium Production  thermal medium radiating from around Tc with meltedr , well-boundJ/y with large collectivity

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