198 research outputs found
Flash of Prompt Photons from the Early Stage of Heavy-Ion Collisions
We briefly recall the tremendous strides in the studies of the parton cascade
model made by Klaus Geiger. Next, we argue that photons may provide
confirmation of several of these ideas. Thus we know that, copious internetted
partonic cascades may develop in the wake of relativistic collisions of nuclei
at CERN SPS and BNL RHIC energies, We use the parton cascade model to estimate
the emission of single photons generated from such cascades due to the
branching of quarks , scattering of quarks and gluons, and
annihilation of quarks. The formation of a hot and dense partonic matter is
shown to be preceded by an intense radiation of photons from the QED branching
of quarks. This is similar to the QCD branching which along with the
gluon multiplication () which is known to play a crucial role in the
formation of the dense partonic plasma.Comment: 14 pages, including 4 figures. Contribution to Proceedings of ``Kay
Kay Gee Day- Klaus Kinder-Geiger Memorial Workshop'' held at Brookhaven
National Lab, October 23, 199
Scaling of single photon production in hadronic collisions
Scaling of single photon production in and collisions is
studied. It is empirically observed the available data scales for and for larger . The NLO pQCD predictions for
collisions at of 200 and 5500 GeV, relevant for RHIC and LHC
energies are seen to closely follow this scaling behaviour. Implications for
single photon production in heavy ion collisions are discussed.Comment: 4 pages including 5 figures. Figure 5 changed to include correct
two-loop contributions. (Submitted to Eur. Phys. J. C.
Single Photons from Relativistic Heavy Ion Collisions and Quark-Hadron Phase Transition
The present status of theoretical expectations of studies of single photons
from relativistic heavy ion collisions is discussed. It is argued that the
upper limit of single photon radiation from S+Au collisions at CERN SPS
obtained by the WA80 collaboration perhaps rules out any reasonable description
of the collision process which does not involve a phase transition to quark
gluon plasma. Predictions for single photons from the quark-matter likely to be
created in collision of two lead nuclei at RHIC and LHC energies are given with
a proper accounting of chemical equilibration and transverse expansion.
Finally, it is pointed out that, contrary to the popular belief of a
quadrilateral dependence of electromagnetic radiations () from such
collisions on the number of charged particles (, we may only have
.Comment: Invited Talk given at Third International Conference on Physics and
Astrophysics of Quark Gluon Plasma, Jaipur, India, March 199
A Second Look at Single Photon Production in S+Au Collisions at 200 AGeV and Implications for Quark Hadron Phase Transition
We reanalyze the production of single photons in S+Au collisions at CERN SPS
to investigate: i) the consequences of using a much richer equation of state
for hadrons than the one used in an earlier study by us; and, ii) to see if the
recent estimates of photon production in quark-matter (at two loop level) by
Aurenche et al. are consistent with the upper limit of the photon production
measured by the WA80 experiment. We find that the measured upper limit is
consistent with a quark hadron phase transition. The measured upper limit is
also consistent with a scenario where no phase transition takes place, but
where the hadronic matter reaches a density of several hadrons per unit volume;
which is rather unphysical.Comment: 10 pages, including 3 figures; Submitted to Euro. Phys. Jour.
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