Coherent photon bremsstrahlung and dynamics of heavy-ion collisions: Comparison of different models

Eichmann, U.; Ernst, Christoph; Satarov, L. M.; Greiner, Walter

doi:10.1103/physrevc.62.044902

Cited by 4 publications

(6 citation statements)

References 14 publications

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“…Finally, let us mention, that bremsstrahlung from the HHG seems to affect only the photon production rate at small energies below about 100 MeV [86,87].…”

Section: Thermal Rates From the Hadron Gasmentioning

confidence: 98%

Direct photons from relativistic heavy-ion collisions

2002

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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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“…Finally, let us mention, that bremsstrahlung from the HHG seems to affect only the photon production rate at small energies below about 100 MeV [86,87].…”

Section: Thermal Rates From the Hadron Gasmentioning

confidence: 98%

Direct photons from relativistic heavy-ion collisions

2002

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“…Our procedure yields the value of stopping around S = 0.537 -0.585, which is close enough to the value 0.547 from UrQMD in Eq. (12). So, with our extraction procedure to separate the charged baryon and charged meson contribution, soft bremsstrahlung from nuclear collisions can definitely be used to probe the degree of stopping.…”

Section: Inference Of Charge Vs Baryon Stoppingmentioning

confidence: 99%

“…In [11] and [12], various models for the time evolution of heavy ion collisions at RHIC were used. There are also some similar earlier works on the subject using numerical dynamical models but at lower energies [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Bremsstrahlung from a microscopic model of relativistic heavy ion collisions

et al. 2000

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We compute bremsstrahlung arising from the acceleration of individual charged baryons and mesons during the time evolution of high-energy Au+Au collisions at the Relativistic Heavy Ion Collider using a microscopic transport model. We elucidate the connection between bremsstrahlung and charge stopping by colliding artificial pure proton on pure neutron nuclei. From the intensity of low energy bremsstrahlung, the time scale and the degree of stopping could be accurately extracted without measuring any hadronic observables. 13.85.Qk

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“…On the other hand, photons do not suffer from strong interactions, and the so-called direct photons are considered to carry information about the early stages of collisions. Numerous studies in this line have been carried out from the early days of the relativistic heavy ion program [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. See [19] for a recent review on this subject and also the references therein.…”

Section: Introductionmentioning

confidence: 99%

“…Among the various mechanisms for producing direct photons, we consider bremsstrahlung radiation. This process is usually modeled as classical radiation from the decelerated protons of the incident nuclei [2][3][4][5][6][7][8][9][10][11]. In [20], the authors focused on the behavior of the higher energy (1 GeV) photons, which are dominantly produced by the incoherent sum of the bremsstrahlung radiation from individual decelerated protons, reproducing the spectrum of the observed radiation [21].…”

Section: Introductionmentioning

confidence: 99%

Anisotropy of low energy direct photons in relativistic heavy ion collisions

Koide

Kodama

2016

J. Phys. G: Nucl. Part. Phys.

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We investigate the behavior of low energy photons radiated by the deceleration processes of two colliding nuclei in relativistic heavy ion collisions using the Wigner function approach for electromagnetic radiation fields. The angular distribution reveals the information of the initial geometric configurations. Such a property is reflected in the anisotropic parameter v2, showing an increasing v2 as energy decreases, which is a behavior qualitatively different from v2 from hadrons produced in the collisions.

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Coherent photon bremsstrahlung and dynamics of heavy-ion collisions: Comparison of different models

Abstract: It is shown that at the AGS energy the coherent photon bremsstrahlung exceeds the photon yield from π 0 -decays at photon energies ω < ∼ 50 MeV.

Cited by 4 publications

References 14 publications

Direct photons from relativistic heavy-ion collisions

Direct photons from relativistic heavy-ion collisions

Bremsstrahlung from a microscopic model of relativistic heavy ion collisions

Anisotropy of low energy direct photons in relativistic heavy ion collisions

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