july 2007workshop of european research group on ultra-relativistic heavy ion physics, nantes, france...

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

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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


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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.


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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-thermal photons (intermediate pT): ??? 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


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Prompt photons: RHIC and D0 pp data

Srivastava’s fit does not describe D0 data at xT>0.1


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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


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Generator of Prompt Photons (GePP): results

Comparison with RHIC data Prediction for LHC


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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, 433bremsstrahlung

dN/d4xd3p s exp(-E/T) T2/E, PL B510, 98 Thermal rates from hot hadron gas:

effective theory for hadron interactionsπρ πγ, ππ ργ, ρ ππγ, ω πγdN/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


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Thermal production rates from HHG

C.Song and G.Fai, Phys.Rev., C58 (1998) 1689.

parameterizations for the processes ππ →ργ , πρ → πγ, and ρ →ππγ , in which the a1 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


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Bjorken -(1+1)-hydrodynamics

Proper time and rapidity y Phys.Rev., D27 (1983) 140

There is no dependence onLorenz boost variable y:

Landau hydrodynamical model, viscosity and conductivity are neglected


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Photon spectrumPhoton 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 , T0 and Tf (at freeze-out)

Connection with the local rest frame

Realization: GeTP.C macros for ROOT


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Generator of Thermal Photons (GeTP): results

Choosing T0 and 0 one can fit data in the hadron scenario

comparison with data, Tf = 100 MeV


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GeTP: prediction for LHC


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GeTP: sensitivity to the parameters

sensitivity to T0 sensitivity to Tf


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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.


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Back up


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Compton Annihilation

In p+p Hard photons:direct component

q + g + q q + q + g

Photons in A+A

Direct Photons Decay Photons

hard thermal hard+thermal

QGP Hadron gasdirect fragmentation

Preequilibriumphotons

jet--conv.

Medium induced bremsstr.

In A+A picture is much more complicated:

V2=0V2<0V2<0

V2>0V2>0V2>0

july 2007workshop of european research group on ultra-relativistic heavy ion physics, nantes, france...

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