S. V. S. Sastry

Hard photon production from unsaturated quark gluon plasma at two loop level

Abstract The hard photon production from bremsstrahlung and annihilation with scattering that arise at two-loop level are estimated for a chemically non-equilibrated quark–gluon plasma in the framework of Hard Thermal Loop (HTL) resummed effective field theory. The rate of photon production is found to be suppressed due to unsaturated phase space compared to equilibrated plasma. For an unsaturated plasma, unlike the effective one-loop case, the reduction in the effective two-loop processes is found to be independent of gluon fugacity, due to an additional collinear enhancement arising from the decrease in thermal quark mass but strongly depends on quark and antiquark fugacities. It is also found that the photon production is dominated by bremsstrahlung mechanism, since the phase space suppression is higher for annihilation with scattering, in contrast to the equilibrated plasma where annihilation with scattering dominates the photon production.

Photon production from quark gluon plasma at finite baryon density

The photon yield from a baryon-rich quark gluon plasma (QGP) at SPS energy has been estimated. In the QGP phase, rate of photon production is evaluated up to two-loop level. In the hadron phase, dominant contribution from π,ρ, ω mesons has been considered. The evolution of the plasma has been studied with appropriate equation of state in both QGP and hadron phase for a baryon-rich system. At SPS energy, the total photon yield is found to increase marginally in the presence of baryon density.

L-dependent heavy ion fusion potentials

The energyE and angular momentuml dependence of optical potential for fusion of16O+208Pb system, observed by Christleyet al [5], is expressed as a function of radial kinetic energy (ɛ) instead of explicitE andl dependence. It is shown that the effects of different channel couplings, which result in different effective potentials, can also be parametrized as a function ofɛ. A correlation is obtained between the energy dependent part of this effective potential and the maximum of the spin enhancement around the Coulomb barrier and both these quantities depend on the details of the channel couplings.

Adiabatic heavy-ion fusion potentials for fusion at deep sub-barrier energies

The recently reported unusual behaviour of fusion cross-sections at extreme sub-barrier energies has been examined. The adiabatic limit of fusion barriers has been determined from experimental data using the barrier penetration model. These adiabatic barriers are consistent with the adiabatic fusion barriers derived from the modified Wilzynska-Wilzynski prescription. The fusion barrier systematics has been obtained for a wide range of heavy-ion systems.

Empirical emission functions for Landau-Pomeranchuk-Migdal suppression of photon emission from quark-gluon plasmas

The Landau-Pomeranchuk-Migdal (LPM) suppression of photon emission rates from the quark-gluon plasma have been studied at different temperatures and chemical potentials. The integral equation for the transverse vector function

Modified WKB transmission for fusion

\mathbf{f}\ifmmode \tilde{}\else \~{}\fi{}({\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\mathbf{p}}}_{\ensuremath{\perp}})

Effective potentials and threshold anomaly

consisting of multiple scattering effects is solved for the parameter set

A new approach for heavy ion fusion spin distribution

{{p}_{\ensuremath{\Vert}},k,\ensuremath{\kappa},T},

A new polarization potential for heavy ion fusion spin distribution

for bremsstrahlung and off-shell annihilation (aws) processes. The integrated

Experimental determination of energy-dependent barriers for fusion.

{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\mathbf{p}}}_{\ensuremath{\perp}}\ensuremath{\cdot}\mathbf{f}\ifmmode \tilde{}\else \~{}\fi{}({\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\mathbf{p}}}_{\ensuremath{\perp}})