Direct hadron production in ultrarelativistic heavy-ion collisions

Peressounko, D. Yu.; Pokrovsky, Yu. E.

doi:10.1016/s0375-9474(97)00468-5

Cited by 10 publications

(30 citation statements)

References 9 publications

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“…Because the rates are proportional to exp(− p · u/T ), where p is the four momentum of the photon and u is the flow four-velocity, stronger transverse flow allows lower temperatures to produce equal yield at high p T . Peressounko & Pokrovsky (128) argued the necessity of such an initial flow, and Alam et al (127) and Chaudhuri (129) later studied its effects. It can be argued that gradients in initial particle production would lead to buildup of flow during thermalization, but it is very difficult to quantify how large flow velocities could build up this way.…”

Section: Photons At Spsmentioning

confidence: 99%

“…Direct photon production in √ s N N = 17.3 GeV Pb+Pb collisions at the CERN-SPS was measured by the WA98 collaboration (127). Several authors have compared this data with hydrodynamical calculations (128)(129)(130)(131)(132). All authors agreed that the photon spectrum could be explained if one assumes sufficiently hot (T > 200 MeV) initial state, but the required initial temperature varied largely from T ∼ 200 MeV (129) to T = 335 MeV (128).…”

Section: Photons At Spsmentioning

confidence: 99%

“…The hadron spectra were reproduced in References (130,132), and, when no initial transverse flow is assumed, also in Reference (129). In the other two cal-culations (128,131), the initial state was only required to have the same entropy as the final-state particles.…”

Section: Photons At Spsmentioning

confidence: 99%

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Hydrodynamic Models for Heavy Ion Collisions

Huovinen

Ruuskanen

2006

Annu. Rev. Nucl. Part. Sci.

364

373

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Section: Photons At Spsmentioning

confidence: 99%

Section: Photons At Spsmentioning

confidence: 99%

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Hydrodynamic Models for Heavy Ion Collisions

Huovinen

Ruuskanen

2006

Annu. Rev. Nucl. Part. Sci.

364

373

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“…It will be shown that WA98 single photon data could be well explained in this scenario, with reasonable hadron density, if one assumes a small initial fluid velocity. In [11] initial velocity distribution was assumed to be linearly increasing. We assume that at the beginning of one fluid hydrodynamic stage, initial radial velocity follows the distribution of initial energy density, which we assume to be of Woods-Saxon form, with radius and diffuseness parameters, R = 6.4f m and a = 0.54f m. In [11] hadronic equation of state comprises all the hadrons in the particle data book.…”

mentioning

confidence: 99%

“…In [11] initial velocity distribution was assumed to be linearly increasing. We assume that at the beginning of one fluid hydrodynamic stage, initial radial velocity follows the distribution of initial energy density, which we assume to be of Woods-Saxon form, with radius and diffuseness parameters, R = 6.4f m and a = 0.54f m. In [11] hadronic equation of state comprises all the hadrons in the particle data book. We choose to use hadrons up to mass 2 GeV.…”

mentioning

confidence: 99%

Single photons from Pb Pb collisions at CERN SPS: quark gluon plasma versus hadronic gas

Chaudhuri

2003

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

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In a hydrodynamic model, we have analyzed the direct photon data obtained by the WA98 collaboration in 158 A GeV Pb+Pb collisions at CERN SPS. The transverse expansion of the system was taken into account. Two scenarios, (i) formation of quark-gluon plasma and (ii) formation of hot hadronic gas, were considered. Both the scenarios describe the data equally well. However, hadronic gas scenario require very high initial temperature (∼ 300 MeV) and it is difficult to conceive existence of hadron gas at that high temperature.If the hadronic fluid has small radial velocity (0.2c-0.3c) initially, the data are well explained in the hadronic gas scenario with reasonable initial temperatures.PACS numbers(s): 12.38.Mh,13.85.Qk,24.85.+p, Recently WA98 collaboration has published their single photon emission data for 158 A GeV Pb+Pb collisions at CERN SPS [1]. Much interest was aroused after the publication of the WA80 preliminary results of the S+Au single photon data [2], as it was hoped that the they can be a conclusive probe of the much debated quark-gluon plasma (QGP), expected to be produced in relativistic heavy ion collisions. The preliminary data were analyzed by several authors. Xiong and Shuryak [3] analyzed the data assuming a mixed phase formation and found excess photons. Srivastava and Sinha [4] analyzed the data considering two possible scenarios after the collision, one with the phase transition to QGP, the other without it. It was claimed that the data were explained only in the phase transition scenario. We had also analyzed the preliminary versions of the WA80 direct photon data [5]. It was shown that formation of viscous hadron gas in the initial state, can explain the data. The revised version of the data [6] were also analyzed by several authors including us [7]. It was concluded that the data are not sensitive enough to discriminate between the two alternate pictures, e.g. formation of quark-gluon plasma and formation of hot hadronic gas.Several authors have analyzed the recent WA98 single photon data [8][9][10][11]. Peressounko et al [11] concluded that the data could be explained only with a small initial radial velocity. Also the data could not distinguish between a QGP and a hot hadronic gas scenario. Srivastava et al [8] could fit the data in the QGP scenari, without initial radial velocity. But the two loop photon rate used by them was not corrected for a factor of 4. They did not considered the hadronic scenario. They argued that in the pure hadronic scenario, initial temperature of the hadronic fluid will be large. Hadronic density will be ∼ 10 hadrons/f m 3 . It is unphysical to consider hadronic gas at such a high density. Initial Hadronic scenario was considered in [9]. It was concluded that only hadronic model with medium modification (hadrons were formed with zero mass) could explain the data.In the present paper we analyze the WA98 single photon data in the no phase transition (NPT) scenario. A hot hadronic gas is assumed to be formed in the initial state. It expands, cools and freezes o...

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Direct photon production in heavy-ion reactions at SPS and RHIC

Peitzmann

2003

Pramana - J Phys

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Abstract.A review on experimental results for direct photon production in heavy ion reactions is given. A brief survey of early direct photon limits from SPS experiments is presented. The first measurement of direct photons in heavy ion reactions from the WA98 collaboration is discussed and compared to theoretical calculations. An outlook on the perspective of photon measurements at RHIC is given.

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Direct hadron production in ultrarelativistic heavy-ion collisions

Abstract: Hadrons emitted by the pre-surface layer of quark-gluon plasma (QGP) before phase transition into hadronic gas are considered as possible source of direct information about QGP. It is shown that these hadrons dominate at soft p t if QGP is created in ultrarelativistic heavy ion collisions.

Cited by 10 publications

References 9 publications

Hydrodynamic Models for Heavy Ion Collisions

Hydrodynamic Models for Heavy Ion Collisions

Single photons from Pb Pb collisions at CERN SPS: quark gluon plasma versus hadronic gas

Direct photon production in heavy-ion reactions at SPS and RHIC

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