Direct photons for FASTMC

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

2. Introduction - UHKM package • Universal Hydro Kinetic Model (UHKM) (http://uhkm.jinr.ru). 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 Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev

3. Introduction - photons for UHKM • decay photons: trivial (π0, , … decays) • prompt photons (high pT): p+p – data fit & A+B – binary scaling • thermal photons (low pT): 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-thermalphotons (intermediate pT): ??? Should think how jet-γ conversion, jet-bremsstrahlung could be implemented in UHKM. • ITEP group has prepared for FASTMC: prompt photons thermal photonsfrom HHG in Bjorken -(1+1)-hydrodynamics • Have been implemented into FASTMC by Ludmila Malinina Workshop 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 xT>0.1 Workshop 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/0609037 (√s)5 Ed3σ/d3p = F(xT,y) • One can use a data tabulation of the F(xT,y) to generate prompt photons. • A+B: Ed3N/d3p(b)= Ed3σpp/d3p AB TAB(b)= Ed3σpp/d3p Ncoll(b)/σppin • Nuclear effects (Cronin, quenching, …) are not taken into account. • Realization: GePP.C macros for ROOT Workshop 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 Workshop 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/d4xd3p  s ln(0.23E/sT) exp(-E/T) T2/E, ZP C53, 433 bremsstrahlung dN/d4xd3p  s exp(-E/T) T2/E, PL B510, 98 • Thermal rates from hot hadron gas: effective theory for hadron interactions πρ πγ, ππ ργ, ρ ππγ,ω πγ dN/d4xd3p ~ T2.15 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 Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev

8. Thermal production rates from HHG • C.Song and G.Fai, Phys.Rev., C58 (1998) 1689. parameterizations for theprocesses ππ →ργ , πρ → πγ, and ρ →ππγ , inwhich the a1 meson is takeninto account properly F.D.Steffen and M.H.Thoma, Phys.Lett., B510 (2001) 98. Forhard photons, E >1 GeV, a rough estimateof this sum plus ω πγby the parameterization Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev

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

10. Photon spectrum Photon spectra follow from convoluting the photon productionrates with the space–time evolutionof thecollision For a longitudinallyexpanding cylinder For proper time  and rapidity y` Connection with the local rest frame For anideal hadrongas  Main parameters: initial 0 , T0 and Tf (at freeze-out) Realization:GeTP.C macros for ROOT Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev

11. Generator of Thermal Photons (GeTP): results comparison with data, Tf = 100 MeV Choosing T0 and 0 one can fit data in the hadron scenario Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev

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

13. GeTP: sensitivity to the parameters sensitivity to T0 sensitivityto Tf Workshop 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 T0 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. Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev

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

16. In p+p Hard photons:direct component Annihilation Compton In A+A picture is much more complicated: Photons in A+A Direct Photons Decay Photons Preequilibriumphotons hard thermal hard+thermal direct fragmentation QGP Hadron gas jet-g-conv. Medium inducedg bremsstr. V2=0 V2>0 V2>0 V2>0 Workshop of European Research Group on Ultra-Relativistic Heavy Ion Physics, Nantes, France S.Kiselev V2<0 V2<0