Erratum: Parametrization of thermal photon emission rates from mesonic matter

Direct photons have been proposed as a promising signature for the quark-gluon plasma (QGP) formation in relativistic heavy-ion collisions. Recently WA98 presented the first data on direct photons in P b+P b-collisions at SPS. At the same time RHIC started with its experimental program. The discovery of the QGP in these experiments relies on a comparison of data with theoretical predictions for QGP signals. In the case of direct photons new results for the production rates of thermal photons from the QGP and a hot hadron gas as well as for prompt photons from initial hard parton scatterings have been proposed recently. Based on these rates a variety of different hydrodynamic models, describing the space-time evolution of the fireball, have been adopted for calculating the direct photon spectra. The results have been compared to the WA98 data and predictions for RHIC and LHC have been made. So far the conclusions of the various models are controversial.The aim of the present review is to provide a comprehensive and up-to-date survey and status report on the experimental and theoretical aspects of direct photons in relativistic heavy-ion collisions. References 83Now we will discuss the various attempts for calculating the production rate of energetic photons (E ≫ T ) from an equilibrated QGP.Pre-HTL rate: Before the invention of the Hard-Thermal-Loop (HTL) improved perturbation theory (see below), the QGP photon rates have been calculated using the perturbative matrix elements for the processes of Fig. 1 together with Eq.(2) [15,16,20,22]. In Ref.[20], even bremsstrahlung has been considered in this way. The derivation of the differential production rate of energetic photons (E ≫ T ), 4 The strong coupling constant at finite temperature depends on the temperature (effective, temperature-dependent running coupling constant) [29]. However, for most applications in the following we will use a mean value of α s = 0.2 -0.5, which is typical for temperatures reachable in relativistic heavy-ion collisions.7 In Ref.[49] a numerical error led to an overestimation of the rate by a factor of 4 [51].

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“…Alternatively the sum of the rates from Ref. [71,76] -the rates in Ref. [76] are not given analytically -can be used.…”

Section: Thermal Rates From the Hadron Gasmentioning

confidence: 99%

Direct photons from relativistic heavy-ion collisions

2002

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“…In order to calculate the photon spectrum from the fireball when the LQCD EoS is used, one has to know also the photon production rate from the hot hadron gas since photons will also be emitted from this thermal phase following the QGP. We use the simple estimate for the photon production rate given by Steffen and Thoma [42], which reproduces the sum of production rates for the processes ππ → ργ, πρ → πγ and ρ → ππγ calculated in [43]. The estimate for the production rate reads…”

Section: B Photon Productionmentioning

confidence: 99%

Thermal photon production in Au+Au collisions: Viscous corrections in two different hydrodynamic formalisms

Peralta-Ramos¹,

Nakwacki²

2011

Nuclear Physics A

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We calculate the spectra of produced thermal photons in Au+Au collisions taking into account the nonequilibrium contribution to photon production due to finite shear viscosity. The evolution of the fireball is modeled by second-order as well as by divergence-type 2+1 dissipative hydrodynamics, both with an ideal equation of state and with one based on Lattice QCD that includes an analytical crossover. The spectrum calculated in the divergence-type theory is considerably enhanced with respect to the one calculated in the second-order theory, the difference being entirely due to differences in the viscous corrections to photon production. Our results show that the differences in hydrodynamic formalisms are an important source of uncertainty in the extraction of the value of η/s from measured photon spectra. The uncertainty in the value of η/s associated with different hydrodynamic models used to compute thermal photon spectra is larger than the one occurring in matching hadron elliptic flow to RHIC data.

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Out-of-equilibrium photon production from disoriented chiral condensates

Lee

2000

Physics Letters B

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Erratum: Parametrization of thermal photon emission rates from mesonic matter

Cited by 11 publications

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Direct photons from relativistic heavy-ion collisions

Direct photons from relativistic heavy-ion collisions

Thermal photon production in Au+Au collisions: Viscous corrections in two different hydrodynamic formalisms

Out-of-equilibrium photon production from disoriented chiral condensates

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