Limits on the Production of Direct Photons in 200<i>A</i>GeV<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>S</mml:mi></mml:mrow><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>32</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow><mml:mo>+</mml:mo><mml:mi>A</mml:mi><mml:mi>u</mml:mi></mml:math>Collisions

The formulation of the real and virtual photon production rate from strongly interacting matter is presented in the framework of finite temperature field theory. The changes in the hadronic spectral function induced by temperature are discussed within the ambit of the Walecka type model, gauged linear and non-linear sigma models, hidden local symmetry approach, and QCD sum rule approach. The possibility of observing the direct thermal photon and lepton pairs from quark gluon plasma has been contrasted with those from hot hadronic matter with and without medium effects for various mass variation scenarios. At SPS energies, in-medium effects of different magnitude on the hadronic properties for the Walecka model, Brown Rho scaling, and Nambu scaling scenarios are conspicuously visible through the low invariant mass distribution of dileptons and transverse momentum spectra of photons. However, at RHIC energies the thermal photon (dilepton) spectra originating from quark gluon plasma overshines those from hadronic matter for large transverse momentum (invariant mass) irrespective of the models used for evaluating the finite temperature effects on the hadronic properties. It is thus expected that at both RHIC and LHC energies the formation of quark gluon plasma in the initial stages may indeed turn out to be a realistic scenario. Static dilepton spectra. 8.4. Photon and dilepton spectra with space-time evolution. 9. Summary and outlook. Appendix: Thermal propagators.

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“…Ref. [155]) such effects are not relevant at present. Therefore, we have neglected it in the following discussions.…”

Section: The Total Photon Emission Rate From Qgp and Hadronic Matter mentioning

confidence: 85%

Thermal Photons and Lepton Pairs from Quark Gluon Plasma and Hot Hadronic Matter

et al. 2000

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“…The major systematic error then arises from the uncertainty in the π 0 and η abundances. The contributions from other mesons are usually estimated from the so-called 'm T scaling', i.e., a ∼exp(−βm T ) dependence of the transverse mass spectra with a universal slope parameter β. Photon measurements at the CERN-SpS have been performed by the HELIOS-2 [262], CERES [263] and WA80/WA98 [264,265] collaborations. In central S+Au, WA80 found a photon excess of 5% ± 5.8%(syst) ± 0.8%(stat) consistent with CERES and HELIOS-2 results which carry somewhat larger errors.…”

Section: Direct Photon Spectramentioning

confidence: 99%

“…[266] (long-dashed curve) which, as mentioned above, strongly overshoot the WA80 bounds due to a high initial temperature in a purely hadronic description with rather few degrees of freedom. On the other hand, using a larger set of hadronic states (including [264]; full and short-dashed curves: transport calculations of Ref. [268] with and without dropping masses, respectively; long-dashed curve: Bjorken-type hydrocalculations with a purely hadronic equation of state including π, η, ρ and ω mesons only [266]; dotted curve: 2+1 dimensional hydro-calculations employing a purely hadronic equation of state with a larger set of mesons as well as baryons [214]; both hydro-approaches have used the photon production rates of Ref.…”

Section: Direct Photon Spectramentioning

confidence: 99%

“…Direct photon spectra, compared to WA80 upper limits[264], in central 200 AGeV S+Au collisions using a simple fireball evolution with thermal rates from the chiral reduction formalism[100] (left panel; solid and dashed curve are obtained with and without the baryonic contributions, respectively) and the in-medium ρ spectral function[47,102,49,123] (right panel).…”

mentioning

confidence: 99%

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Chiral Symmetry Restoration and Dileptons in Relativistic Heavy-Ion Collisions

Rapp

Wambach

2002

Advances in Nuclear Physics

545

258

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The current theoretical status in the analysis and interpretation of low-mass dilepton measurements in (ultra-) relativistic heavy-ion experiments is reviewed. Special emphasis is put on potential signals of (partial) restoration of dynamically broken chiral symmetry in a hot and dense hadronic medium. It follows from chiral symmetry alone that parity partners of hadronic correlation functions must become identical when the symmetry is restored. The assessment of medium effects in the vector channel, which governs the dilepton production, thus necessitates a simultaneous treatment of the vector and axialvector degrees of freedom. While significant progress in this respect has been made some open questions remain in establishing a rigorous link in the mass region below 1 GeV. From the present calculations a suggestive 'quark-hadron duality' emerges near the phase boundary. It implies substantial medium effects in the dilepton signal from the hadronic phase which smoothly matches a perturbative description within the plasma phase.

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“…Experiments to measure direct photons are carried out at the CERN/SPS by the WA80/WA98 and the CERES/NA45 collaborations. Whereas the final analysis of the WA80 collaboration for S+Au indicates a 5% photon signal over background (with a 0.8% statistical and a 5.8% systematical error) [393,394,395] the CERES/NA45 collaboration did not report any direct photons, but sets an upper limit of 7% for the integrated excess an unconventional photon source might have in central S+Au collisions [396,397,398]. The WA80 collaboration has reported upper limits for each measured k t bin which yields important information for constraining the initial temperature of the reaction zone.…”

Section: Experimental Statusmentioning

confidence: 99%

Signatures of quark-gluon plasma formation in high energy heavy-ion collisions: a critical review

Bass

Gyulassy

Stöcker

et al. 1999

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

280

223

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A critical review on signatures of quark-gluon plasma (QGP) formation is given and the current (1998) experimental status is discussed. After giving an introduction to the properties of QCD matter in both, equilibrium and non-equilibrium theories, we focus on observables which may yield experimental evidence for QGP formation. For each individual observable the discussion is divided into three sections: first the connection between the respective observable and QGP formation in terms of the underlying theoretical concepts is given, then the relevant experimental results are reviewed and finally the current status concerning the interpretation of both, theory and experiment, is discussed. A comprehensive summary including an outlook towards RHIC is given in the final section.

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Limits on the Production of Direct Photons in 200AGeVS32+AuCollisions

Cited by 96 publications

References 17 publications

Thermal Photons and Lepton Pairs from Quark Gluon Plasma and Hot Hadronic Matter

Thermal Photons and Lepton Pairs from Quark Gluon Plasma and Hot Hadronic Matter

Chiral Symmetry Restoration and Dileptons in Relativistic Heavy-Ion Collisions

Signatures of quark-gluon plasma formation in high energy heavy-ion collisions: a critical review

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