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Advances in High Energy Physics
Volume 2013, Article ID 176578, 41 pages
http://dx.doi.org/10.1155/2013/176578
Review Article

Electromagnetic Radiations from Heavy Ion Collision

1HENPP Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata 700064, India
2Theoretical Physics Division, Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata 700064, India
3Ctr. for Astroparticle Physics and Space Bose Institute, 5/EN Bidhan Nagar, Kolkata 700091, India

Received 15 April 2013; Accepted 5 July 2013

Academic Editor: Jan E. Alam

Copyright © 2013 Payal Mohanty et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In this review, we have discussed the different sources of photons and dileptons produced in heavy ion collision (HIC). The transverse momentum () spectra of photons for different collision energies are analyzed with a view of extracting the thermal properties of the system formed in HIC. We showed the effect of viscosity on spectra of produced thermal photons. The dilepton productions from hot hadrons are considered including the spectral change of light vector mesons in the thermal bath. We have analyzed the and invariant mass () spectra of dileptons for different collision energies too. As the individual spectra are constrained by certain unambiguous hydrodynamical inputs, so we evaluated the ratio of photon to dilepton spectra, , to overcome those quantities. We argue that the variation of the radial velocity extracted from with is indicative of a phase transition from the initially produced partons to hadrons. In the calculations of interferometry involving dilepton pairs, it is argued that the nonmonotonic variation of HBT radii with invariant mass of the lepton pairs signals the formation of quark gluon plasma in HIC. Elliptic flow () of dilepton is also studied at  TeV for 30–40% centrality using the hydrodynamical model.