28.05.08ITEP meeting S.Kiselev1 Fast generators of direct photons Sergey Kiselev, ITEP, Moscow ...
-
Upload
isaac-sharp -
Category
Documents
-
view
219 -
download
0
Transcript of 28.05.08ITEP meeting S.Kiselev1 Fast generators of direct photons Sergey Kiselev, ITEP, Moscow ...
28.05.08 ITEP meeting S.Kiselev 1
Fast generators of direct photons
Sergey Kiselev, ITEP, Moscow Introduction
Definitions SPS and RHIC data New processes
Prompt photons Thermal photons in 1+1 hydrodynamics
Hot Hadron Gas (HHG) scenario Qurk Gluon Plasma (QGP) scenario
To do
Introduction
28.05.08 ITEP meeting S.Kiselev 2
28.05.08 ITEP meeting S.Kiselev 3
Introduction - definitions
Direct photons: not from hadron decays Quark gluon level:
qq gγ, qg qγ, qq(g) qq(g)γ.
Initial hard NN collisions, pQCD prompt γ Thermalised QGP stage thermal γ from QGP.
28.05.08 ITEP meeting S.Kiselev 4
Introduction – definitions
Hadron level: meson scatterings: ππ ργ, πρ πγ, πK K* γ, Kρ
Kγ, KK* πγ, πK* Kγ, . . . Thermalised hadron stage thermal γ from HHG
Decay photons: Long lived (c » cAB ~ 50-100 fm)
π0 γγ, γγ, ’ ργ/ωγ/2γ Shot lived (c cAB ~ 50-100 fm)
ω πγ, a1 πγ, Δ Nγ, K* Kγ, γ, ρ ππγ, . . .
Introduction – SPS data
28.05.08 ITEP meeting S.Kiselev 5
Introduction – RHIC data
28.05.08 ITEP meeting S.Kiselev 6
28.05.08 ITEP meeting S.Kiselev 7
Photons in A+A
Direct PhotonsDecay Photons
hard thermal hard+thermal
QGP Hadron gas`direct` fragmentation
Preequilibriumphotons ???
jet--conv.
Medium induced bremsstr.
Introduction - new processes at RHIC
Hard scattered parton interacts with gluon in bulk matter
28.05.08 ITEP meeting S.Kiselev 8
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
28.05.08 ITEP meeting S.Kiselev 9
Generator of Prompt Photons (GePP): results
Comparison with RHIC data Prediction for LHC
28.05.08 ITEP meeting S.Kiselev 10
Bjorken -(1+1)-HydroDynamics (BHD)
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
28.05.08 ITEP meeting S.Kiselev 11
Photon spectrum in BHDPhoton 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 gas
Main parameters: initial 0 , T0 and Tf (at freeze-out)
Connection with the local rest frame
Input function – production rate E dN/d4xd3p (E,T)
Phys.Rep.364(2002)98
28.05.08 ITEP meeting S.Kiselev 12
HHG scenario
C.Song, Phys.Rev.C47(1993)2861 an effective chiral Lagrangian with π, ρ and a1 mesons to calculate the processes ππ →ργ , πρ → πγ, and ρ →ππγ .
C.Song and G.Fai, Phys.Rev.C58(1998)1689.
parameterizations for photon rates.
Realization: GeT_HHG.C macros for ROOT
28.05.08 ITEP meeting S.Kiselev 13
GeT_HHG: comparison with SPS and RHIC
Choosing T0 and 0 one can fit data in the hadron scenario
comparison with data, Tf = 100 MeV
28.05.08 ITEP meeting S.Kiselev 14
GeT_HHG: prediction for LHC
28.05.08 ITEP meeting S.Kiselev 15
GeT_HHG: sensitivity to the parameters
sensitivity to T0 sensitivity to Tf
28.05.08 ITEP meeting S.Kiselev 16
QGP scenario: QGP and HHG phasesQGP: ideal massless parton gas (µq =0) HHG: ideal massless pion gas
First order phase transition at critical temperature Tc
B bag constant
Nc colorsNf flavors
g number of degrees of freedom
QGP scenario: mixed phase
28.05.08 ITEP meeting S.Kiselev 17
Mixed phase
Main parameters: initial 0 , T0 , Tc and Tf
Rates from QGP -1st order
28.05.08 ITEP meeting S.Kiselev 18
Perturbative thermal QCD applyingHard thermal loop (HTL) resummation
Phys.Lett.B510(2001)98
Rates from QGP -2nd order
28.05.08 ITEP meeting S.Kiselev 19
Thermal photon production in the QGP is a non-perturbative mechanism that can not be accessed in perturbative HTL resummed thermal field theory
2-loop contribution is the same order in αs
One must consider the QGP rates as an educated guess
To do
28.05.08 ITEP meeting S.Kiselev 20
• Write and test the macros GeT_QGP.C• Think on the “hard+thermal” generator