Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 1 Direct photons for the UHKM package  Sergey Kiselev, ITEP, Moscow  Direct photon news new experimental techniques new physical processes new data  Photons for the UHKM package decay γ prompt γ thermal γ hard-thermal γ  Conclusions

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 2 New experimental techniques  Last years: large progress in experimental techniques to extract direct photons  Direct photons have been revealed by methods: Subtraction, WA98/2000, PHENIX/2005 Momentum correlation, WA98/2004 Internal conversion, PHENIX/2005, QM’05 External conversion, PHENIX/2006, QM’06 Tagging, PHENIX/2006, QM’06

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 3 Photons in A+A Direct PhotonsDecay Photons hardthermalhard+thermal QGPHadron gas`direct`fragmentation Preequilibrium photons ??? jet-  - conv. Medium induced  bremsstr. New physical processes Hard scattered parton interacts with gluon in bulk matter

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 4 New physical processes - RHIC PR C (2004) S.Turbide et al hep-ph/

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 5 New data – R AA  R AA seems to be below unity at very high-p T (p T > 14 GeV/c)  None of the theoretical calculations reproduces R AA in the full p T range First data using p+p data as reference! Nucl-ex/

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 6 New data – v 2 S.Turbide, C.Gale, R.J.Fries, PRL (2006) Within statistical and systematic errors v 2 is consistent with zero. v 2 =0 or cancellation of different contributions?

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 7 UHKM package  Universal Hydro Kinetic Model (UHKM) ( Now includes: FASTMC – FAST Monte-Carlo hadron freeze-out generator. Particles are generated on the chemical or thermal freeze-out hyper-surface represented by a parameterization or a numerical solution of relativistic hydrodynamics. UKM – Universal Kinetic Model. Treats further evolution (scattering and decays) solving relativistic Boltzmann equations numerically. SPHES – Smoothed Particle Hydrodynamics Equations Solver. Solves (1+3D) – relativistic perfect hydrodynamics equations at given initial condition and equation of state and provides hadron freeze-out hyper-surface.

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 8 photons for UHKM  decay photons: trivial (π 0, , … decays)  prompt photons (high p T ): p+p – data fit A+B – binary scaling  thermal photons (low p T ): thermal rates from QGP/HadronGas have to be convoluted over the space-time history of the A+B reaction given by hydrodynamics  hard-thermal (intermediate p T ): ? Should think how jet-γ conversion, jet- bremsstrahlung could be implemented in UHKM. L.Malinina plans to implement jets. May be, in parallel, one can think on direct photon source.

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 9 Prompt photons: data fit A Compilation of Data, J. Phys. G, 23 (1997) A1 Data fit: D.Srivastava, Eur.Phys.J, C22 (2001) 129 A+B: Ed 3 N/d 3 p(b)=Ed 3 σ pp /d 3 p AB T AB (b)=Ed 3 σ pp /d 3 p N coll (b)/σ pp in p+p:

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 10 Prompt photons: RHIC p+p data

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 11 Thermal photons  Thermal rates from QGP: Perturbative QCD, the lowest order in  s qq  gγ qg  qγ dN/d 4 xd 3 p   s ln(0.23E/  s T) exp(-E/T) T 2 /E, ZP C53, 433 bremsstrahlung dN/d 4 xd 3 p   s exp(-E/T) T 2 /E, PL B510, 98  Thermal rates from HG: effective theory for hadron interactions πρ  πγ ππ  ργ ω  πγ dN/d 4 xd 3 p  T 2.15 exp(-E/T) / exp((1.35 ET) 0.77 ), PL B510, 98  The thermal rates can be convoluted over the space-time history of the A+B reaction given by SPHES

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 12 Conclusions  Progress in the direct photon sector as in experimental methods and theory  One can implement photons in the UHKM package: - decay photons - prompt photons - thermal photons  Should think on the hard-thermal source of photons

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 13 Back up

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 14 There are theoretical predictions with a sizable azimuthal parameter v2 : S.Turbide, C.Gale, R.J.Fries, PRL (2006) R. Chatterjee et al., PRL 96, (2006) Thermal photons are produced throughout the expansion history and reflect quark anisotropy Jets lose more energy where the medium is thicker - more jet-photon conversions (v2 0) 4

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 15 How does PHENIX measure direct photons and v 2 ?  Measure inclusive photon yield, N inc  Measure hadron contribution components  0 and   By Monte Carlo calculate   and  decay background in inclusive sample, N bg  Calculate direct photon excess over hadron decays, R  Measure inclusive and hadron v 2 by reaction plane method  Calculate direct photon v 2 as R * v 2 inc – v 2 BG R = N inc / N BG v 2 dir = R – 1 Use large statistics Run 4 Au+Au data set See also poster 86 by Kentaro Miki 5

Workshop of European Research Group on Ultrarelativistic Heavy Ion Physics Gribov, Poland S.Kiselev 16 Compton Annihilation In p+p Hard photons: direct component Photons in A+A Direct PhotonsDecay Photons hardthermalhard+thermal QGPHadron gasdirectfragmentation Preequilibrium photons jet-  - conv. Medium induced  bremsstr. In A+A picture is much more complicated: V2=0 V2<0 V2>0