Bikash Sinha

Universal signals of a quark-gluon plasma

Abstract It is shown that the ratio of the production rates ( γ μ + μ − ) and ( π 0,± μ + μ − ) from a quark-gluon plasma is independent of the space-time evolution of the plasma fireball and thus universal signals of the quark phase.

The nucleus-nucleus interaction potential using density-dependent delta interaction

Abstract The interaction potential between two nuclei has been calculated by using a generalized folding model. The direct and the exchange terms are computed by folding in Skyrme interaction with the nuclear density distributions and the density matrices of the two nuclei, respectively. A new definition of the one-body optical potential is also suggested. The results agree quite well with standard phenomenology.

The two-body dissipation in second-order perturbation

Abstract An estimate of the two-body dissipation term has been made by calculating the imaginary part of the second-order potential. The folding type of dissipation form factor has been derived by using a suitable two-body delta interaction.

Strangeness in quark-gluon plasma

Abstract It is shown that the signature of quark-gluon plasma, by observing the ratio of K + /K − mesons, will be washed away if the critical temperature for transition is larger than T c ⪆ 160 MeV .

The nucleus-nucleus proximity imaginary potential

Abstract A proximity form of the imaginary potential for two colliding nuclei has been calculated, starting from a two-body effective interaction. The ratio of the imaginary and the real part when scaled by K/μ, the local wave number/effective mass, appears to be a constant independent of the mass of the nuclei.

Nuclear friction and the imaginary part of the nucleus-nucleus interaction potential

Abstract Using semi-classical approximations, the phenomenological form-factor of nuclear friction is derived from the imaginary part of the nucleus-nucleus interaction potential. The results obtained for the friction co-efficient agree well with experimental data on damped collision for two nuclei.

The nuclear response function and dissipation in the Fermi-Gas model

The nuclear response function of a nucleus has been computed in the Fermi Gas model when another nucleus collides with it. A simple relation has been derived for the frictional co-efficient for the later stages of the nucleus-nucleus collision. The results agree quite well with phenomenology and microscopic derivations of the frictional co-efficient.

Nuclear structure calculations using momentum-dependent delta interactions (MDD)

Abstract The ground-state properties of a nucleus have been investigated using momentum- and density-dependent δ-interactions. Unlike the Skyrme type of interaction, the two-body interaction used has terms dependent on the fourth power of the relative momenta. The role of these new terms has been investigated by using the density-matrix expansion technique of Negele and Vautherin. The interaction has been used to calculate, amongst other phenomena, the ion-ion interaction potential and the nucleon-nucleus optical potential. The improvements obtained using such an interaction over the Skyrme II type of interactions (which have small odd state components) are discussed in detail. It is shown that the effective mass, m ∗ , is larger in magnitude than obtained by using the Skyrme II type of interaction. It has been suggested that such interactions could be more appropriate than the Skyrme type of interactions in physical situations where large momentum transfers are involved.

Signals of Quark-Gluon Plasma - Terrestrial and Cosmological

Signals of the Quark-Gluon Plasma, supposedly a state of matter as a result of central collisions of two nuclei at ultrarelativistic energies are investigated with special emphasis on photons, photon pairs and muon pair production. Relics of the events at the primordial epochs of microseconds after the Big Bang origin of the universe, the Quark-Gluon Plasma condensing to hadrons, are investigated. The 7Li production rate is highlighted as a suitable boundary condition for early universe models.

The nuclear response and the imaginary potential for nucleus-nucleus collisions

Abstract The Fermi-gas model is used in this paper to study the nucleus-nucleus collision. The field produced by one of the nuclei is considered to act on nucleons in the other nucleus, which is treated as a Fermi gas of radius R . The imaginary part of the (non-local) nucleus-nucleus potential is then computed by evaluating the energy-conserving second-order term in which the intermediate states are particle-hole excitations produced in the Fermi gas. The equivalent local potential, obtained by using the Perey-Saxon method, is compared with phenomenological imaginary potentials. Later it is shown that, in the limit of small range of non-locality, the imaginary potential can be related to the nuclear response function. With this, one can write the nuclear friction coefficient that is used in phenomenological analyses of heavy-ion collisions in terms of the imaginary potential.