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(Direct) Photons

(Direct) Photons. Photons do not interact strongly Photons have a small cross sections – for production and interactions Two sources of Photons exist: - Photons from decays (e.g. p 0  gg ) - Photons from interactions (direct Photons) There are real Photons and virtual Photons. Gamma Guys.

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(Direct) Photons

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  1. (Direct) Photons • Photons do not interact strongly • Photons have a small cross sections – for production and interactions • Two sources of Photons exist:- Photons from decays (e.g. p0gg)- Photons from interactions (direct Photons) • There are real Photons and virtual Photons

  2. Gamma Guys Joe Kapusta Charles Gale

  3. Hadronic channels Example for a differential cross section:

  4. Partonic channels • from QGP: sensitivity to parton density and temperature • from initial state: sensitivity to PDFs (gluon!) (all quark/anti-quark subprocesses) 4

  5. Differential Photon spectra Clear enhancement of Photon production with QGP

  6. Channel decomposition • Dominant contribution from QGP stage • Long life time of partonic and mixed phase

  7. Comparison to data

  8. Why are short lived hadron resonances interesting? • There is a (long living) hadronic rescattering stage at FAIR and SPS energies • Lifetime and properties of the hadronic stage aredefined and probed by resonance production/absorption/re-feeding/decay • Use different resonances to explore this stage: e.g. mesons: baryons: • Are resonances dissolved/broadened/shifted in matter?

  9. Dileptons and the rho Jochen Wambach Gerry Brown Ralf Rapp

  10. Rho meson spectral function

  11. ‘Trivial’ physics effects • Even without chiral symmetry restaurationand in-medium modifications one expects a modification of the r spectral function

  12. r mass distribution in C(2AGeV)+C • Double hump feature • Strong contribution to low mass r’s from N*1520 • Only small contributions from pp channel UrQMD S. Vogel, M. Bleicher, Phys.Rev.C74:014902,2006

  13. p- r0 p+ r0 r0 r0 p- p+ p- r0 + + + p+ - - - Hadronic vs leptonic channel A+A Hot and dense medium Particle yields L* K K p Particle spectra p p L* time

  14. Decay time distribution ofr mesons Resonance formation needs time (most r from baryon resonances) even short lived resonances are dominantly from later stages

  15. Di-leptons: Some technical issues • Different di-lepton physics:- VMD, EVMD, form factors, - collisional broadening, shining, - explicit r,effective r, instant di-leptons Different result from same input! Standard / consensus needed • Bremsstrahlung?!

  16. Hadronsdi-leptons pi, eta, eta’ Delta rho, omega

  17. Comparison to CERES @ 160 AGeV CERES Data from 2000UrQMD (Pb+Au) is filtered • Well known dip around 500 MeV • Dip is from low momentum di-lepton pairs D. Schumacher, M.B., to be published

  18. NA 60 vs Rapp

  19. HADES energies: UrQMD CC@2AGeV CC@1AGeV • Note the broad r mass distribution D. Schumacher, s. Vogel, M.B, Acta Phys.Hung.A27:451-458,2006

  20. HADES energies: IQMD/RQMD nucl-th/0702004 Phys.Lett.B640:170-175,2006 IQMD, CC@2AGeV(instant di-leptons: no baryon and r resonance propagation) RQMD, CC@2AGeV(effective r, no r and p propagation)

  21. Di-lepton summary • Model differences due to different di-lepton ‘after burner’! • Clear hint of non-equilibrium contributions CC@2AGeV, HADES, nucl-ex/0608031

  22. Event-by-Event fluctuations and hadronisation Sean Gavin Volker Koch, Sangyong Jeon (not on the picture

  23. Motivation At RHIC: look for signals of freely moving partons.(D, CBS,k)At FAIR/SPS:look for the mixed phase and the onset of deconfinement(w, k/p, p/p) E. Bratkovskaya, M.B. et al., PRC 2005

  24. Fluctuations are THE tool!? • Fluctuations might provide information on - deconfinement/confinement- correlation length- thermalization- nature of the QGP- critical point • Is it that easy?- finite time and volume- non-equilibrium- hadronization

  25. Some motivation, some data PHENIX, Au+Au, Ecm=130 AGeV Stephanov, Shuryak et al Lungwitz, Bleicher Hadron gas P(O) Original motivation for E-by-E physics Boring New physics Obser-vable

  26. The tool: qMD • qMD : Quark Molecular Dynamics (a toy model for hadronization) • out-of-equilibrium transport model, (Vlasov equation) • provides a hadronization prescription • essentially realizes a dynamical quark recombination approach

  27. Quark Molecular Dynamics

  28. Trajectories

  29. Hadronization procedure

  30. Some properties: equilibrium Tc ~ 140 MeV

  31. How to model a real collision • For application, use UrQMD initial state • get initial quark distribution from strings • evolve system with qMD • neglect rescattering of hadrons after qMD

  32. Entropy consideration <N> <m>

  33. Entropy and recombination

  34. The idea behind conserved charge fluctuations

  35. Fluctuations and susceptibilities

  36. Comparison to lQCD (I)

  37. Comparison to lQCD (II)

  38. Charge ratio fluctuations

  39. Pion gas, D ~ 4 Quark gas, D ~ 1

  40. Can one observe the fluctuations in the initial state? See e.g. Shuryak et al, Phys.Rev.C63:064903,2001

  41. Experimental results

  42. Recombination and fluctuation parton fraction

  43. Charge transfer fluctuations

  44. qMD results on kappa

  45. Baryon-Strangeness Correlations

  46. Time evolution

  47. Who else… Langanke Achim Richter Mishustin Knoll Sinyukov, Shuryak Blaizot

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