200 likes | 275 Views
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. Introduction - definitions.
E N D
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 ITEP meeting S.Kiselev
Introduction ITEP meeting S.Kiselev
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. ITEP meeting S.Kiselev
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 (ccAB ~ 50-100 fm) ω πγ, a1 πγ, Δ Nγ, K* Kγ, γ, ρ ππγ, . . . ITEP meeting S.Kiselev
Introduction – SPS data ITEP meeting S.Kiselev
Introduction – RHIC data ITEP meeting S.Kiselev
Hard scattered parton interacts with gluon in bulk matter Introduction - new processes at RHIC Photons in A+A Decay Photons Direct Photons jet-g-conv. hard Preequilibriumphotons ??? thermal hard+thermal `direct` fragmentation QGP Hadron gas Medium inducedg bremsstr. ITEP meeting S.Kiselev
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 ITEP meeting S.Kiselev
Generator of Prompt Photons (GePP): results Comparison with RHIC data Prediction for LHC ITEP meeting S.Kiselev
Bjorken -(1+1)-HydroDynamics (BHD) 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 ITEP meeting S.Kiselev
Phys.Rep.364(2002)98 Photon spectrum in BHD Photon spectra follow from convoluting the photon productionrates with the space–time evolutionof thecollision For a longitudinallyexpanding cylinder For proper time and rapidity y` Input function – production rate E dN/d4xd3p (E,T) Connection with the local rest frame For anidealgas Main parameters: initial 0 , T0 and Tf (at freeze-out) ITEP meeting S.Kiselev
HHG scenario • C.Song, Phys.Rev.C47(1993)2861 an effective chiral Lagrangian with π, ρanda1 mesons to calculate theprocesses 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 ITEP meeting S.Kiselev
GeT_HHG: comparison with SPS and RHIC comparison with data, Tf = 100 MeV Choosing T0 and 0 one can fit data in the hadron scenario ITEP meeting S.Kiselev
GeT_HHG: prediction for LHC ITEP meeting S.Kiselev
GeT_HHG: sensitivity to the parameters sensitivity to T0 sensitivityto Tf ITEP meeting S.Kiselev
QGP scenario: QGP and HHG phases QGP: ideal massless parton gas (µq =0) HHG: ideal massless pion gas B bag constant g number of degrees of freedom Nc colors Nf flavors First order phase transition at critical temperature Tc ITEP meeting S.Kiselev
QGP scenario: mixed phase Mixed phase Main parameters: initial 0 , T0 , Tc and Tf ITEP meeting S.Kiselev
Rates from QGP -1st order Phys.Lett.B510(2001)98 Perturbative thermal QCD applying Hard thermal loop (HTL) resummation ITEP meeting S.Kiselev
Rates from QGP -2nd order 2-loop contribution is the same order in αs Thermal photon production in the QGP is a non-perturbative mechanism that can not be accessed in perturbative HTL resummed thermal field theory One must consider the QGP rates as an educated guess ITEP meeting S.Kiselev
To do • Write and test the macros GeT_QGP.C • Think on the “hard+thermal” generator ITEP meeting S.Kiselev