July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 1 Direct photons for FASTMC  Sergey Kiselev, ITEP, Moscow  Introduction  Prompt photons for FASTMC  Thermal photons from hot hadron gas for FASTMC  Conclusions and next steps

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 2 Introduction - 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.

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 3 Introduction - 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/Hot HadronGas (HHG) have to be convoluted over the space-time history of the A+B reaction given by hydrodynamics  hard-thermal photons (intermediate p T ): ??? Should think how jet-γ conversion, jet-bremsstrahlung could be implemented in UHKM.  ITEP group has prepared for FASTMC: prompt photons thermal photons from HHG in Bjorken -(1+1)-hydrodynamics  Have been implemented into FASTMC by Ludmila Malinina

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 4 Prompt photons: RHIC and D0 pp data Srivastava’s fit does not describe D0 data at x T >0.1

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 5 Prompt photons: pp data fit + binary scaling  PHENIX hep-ph/ (√s) 5 Ed 3 σ/d 3 p = F(x T,y)  One can use a data tabulation of the F(x T,y) to generate prompt photons.  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  Nuclear effects (Cronin, quenching, …) are not taken into account.  Realization: GePP.C macros for ROOT

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 6 Generator of Prompt Photons (GePP): results Comparison with RHIC data Prediction for LHC

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 7 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 hot hadron gas: effective theory for hadron interactions πρ  πγ, ππ  ργ, ρ  ππγ, 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

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 8 Thermal production rates from HHG  C.Song and G.Fai, Phys.Rev., C58 (1998) parameterizations for the processes ππ →ργ, πρ → πγ, and ρ →ππγ, in which the a 1 meson is taken into account properly F.D.Steffen and M.H.Thoma, Phys.Lett., B510 (2001) 98. For hard photons, E >1 GeV, a rough estimate of this sum plus ω  πγ by the parameterization

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 9 Bjorken -(1+1)-hydrodynamics Proper time  and rapidity y Phys.Rev., D27 (1983) 140 There is no dependence on Lorenz boost variable y: Landau hydrodynamical model, viscosity and conductivity are neglected

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 10 Photon spectrum Photon spectra follow from convoluting the photon production rates with the space–time evolution of the collision For a longitudinally expanding cylinder For proper time  and rapidity y ` For an ideal hadron gas Main parameters: initial  0, T 0 and T f (at freeze-out) Connection with the local rest frame Realization: GeTP.C macros for ROOT 

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 11 Generator of Thermal Photons (GeTP): results Choosing T 0 and  0 one can fit data in the hadron scenario comparison with data, T f = 100 MeV

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 12 GeTP: prediction for LHC

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 13 GeTP: sensitivity to the parameters sensitivity to T 0 sensitivity to T f

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 14 Conclusions and next steps  In FASTMC one can generate: prompt photons thermal photons from HHG in Bjorken -(1+1)- hydrodynamics  Direct photon data at SPS and RHIC can be reproduced by choosing the T 0 and  0 parameters in the hadron scenario  The thermal photons rates can be easy implemented into more realistic hydrodynamics (SPHES, …)  Next step: thermal photons from HHG in (2+1) – hydrodynamics of FASTMC.

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev 15 Back up

July 2007Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France 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