Single photons, dileptons and hadrons from relativistic heavy ion collisions and quark-hadron phase transition

Abstract

The production of single photons in Pb·Pb collisions at the CERN SPS as measured by the WA98 experiment is analysed. A quark gluon plasma is assumed to be formed initially, which expands, cools, hadronizes, and undergoes freeze-out. A rich hadronic equation of state is used and the transverse expansion of the interacting system is taken into account. The recent estimates of photon production in quark-matter (at two loop level) along with the dominant reactions in the hadronic matter leading to photons are used. About half of the radiated photons are seen to have a thermal origin. The same treatment and the initial conditions provide a very good description to hadronic spectra measured by several groups and the intermediate mass dileptons measured by the NA50 experiment, lending a strong support to the conclusion that quark gluon plasma has been formed in these collisions. Predictions for RHIC and LHC energies are also given.

Free Energy Evolution and Photon Radiation from QGP

“…Thus, the production rate of our model with the flavor = 2 has improved from other works in these two channels. It means that our result is dominant over the production rate of [14,15,18,19,[50][51][52][53][54][55]. The production rate is further examined for the quark flavor = 3 in Figure 6.…”

“…The summation is over the number of quark flavors and is their electric charge. Similarly, the production rate of photons due to two loops order of Bremsstrahlung processes is given as [50][51][52][53]…”

“…Finally, we calculate the most dominant contribution given by annihilation with scattering process (AWS). The expression for production rate of annihilation with scattering is given as [50][51][52][53]…”

“…Lastly, in Figures 9 and 10, we study the total spectra at the temperature = 0.30 GeV as discussed in other works for the different processes of photon spectra for these two different flavors. In these processes, we compare the results with the earlier outputs of other works [14,15,[50][51][52][53][54][55] and also compare results with WA98 direct photon data and photon spectra at RHIC energies measured by PHENIX collaboration [22][23][24][25][26][58][59][60][61][62][63]. In the comparison, we find that the production spectra of our model in the quark flavor = 2 has negligibly visible improvement over the other recent theoretical result of photon spectra in all the corresponding channels like annihilation plus Compton and AWS, but a slight visible improvement is found in the case of Bremsstrahlung.…”

Holographic dilepton production in a thermalizing plasma

“…The (QCD version of the) quantity we compute is measurable in real world experiments and is moreover a very interesting probe of the initial stages of a heavy ion collision; for reviews, see e.g. [17][18][19] and references therein.…”