International Journal of Modern Physics E

Transport models have been very useful in studying the properties of the hot, dense matter that is created in relativistic heavy-ion collisions. We review here a Relativistic Transport (ART) Model and its applications in heavy ion collisions at beam energies below about 10 AGeV available from the Alternating Gradient Synchrotron at Brookhaven National Laboratory. The model allows one to study not only the reaction dynamics leading to the formation of superdense hadronic matter, but also to explore the effects due to the nuclear equation of state and the deformation/orientation of the colliding nuclei on the size and lifetime of the superdense matter. We also discuss the dependence of the central baryon and energy densities, the degree of thermalization, and the collective radial flow velocity of the superdense matter on the beam energy. We further review how the properties of the superdense hadronic matter can be determined from studying the collective flow of nucleons, pions and kaons in these collisions. We finally discuss the mechanisms for kaon production in relativistic heavy-ion collisions and review the progress in extracting the kaon in-medium properties from these collisions.

Any particle is defined by a set of additive quantum numbers: A, L, individual flavours. These numbers could be considered as the components of a vector C which is characteristic of each particle. Each particle is associated to a vector C representing the particle in an abstract space. The electric charge Q could be interpreted as the projection of C on a vector Q(0). If C=0, particle and antiparticle are the same particle. If C≠0, particle and antiparticle are represented by opposite vectors and are different even if Q=0. In this framework, the neutron is different from the antineutron (many experimental facts confirm this statement) and the neutrino is different from the antineutrino. A direct and important consequence of the difference between the neutrino and the antineutrino is that ββ0ν decay should be strictly forbidden. It is indeed in agreement with all up to now experimental results which show no hint of any ββ0ν event. The features of messengers would explain why electromagnetism and strong interaction conserve A, L and individual flavours and consequently also total flavour while weak interaction conserves only A, L and total flavour.

An estimation of the relative probability of electron expulsion from inner shells of atoms following heavy cluster decay or nuclear spontaneous fission is performed. The calculation takes into account the recoil of the daughter nucleus, both in the case of dipole and quadrupole terms. The results show an enhancement of the electron emission probability in comparison with the case of α-decay.

We analyze the elastic scattering angular distributions of the ¹⁶O+¹⁶O system at E_lab=480 MeV and 704 MeV within the framework of the second-order eikonal model based on Coulomb trajectories of colliding nuclei. The diffractive oscillatory structure observed in the elastic angular distribution could be explained due to the interference between the near- and far-side scattering amplitudes. The presence of a nuclear rainbow in this system is evidenced through a classical deflection function. The effective optical potential is developed from the second-order non-eikonal phase shifts.

We compare the inclusive electron neutrino cross sections, ν_e+N_i→X + e^-, averaged over the Michel spectrum for ¹²C, ¹³C, ⁵⁶Fe and ¹²⁷I. We choose these nuclei because terrestrial measurements at LSND and KARMEN have been undertaken for them and these measurements are in reasonable agreement with calculated values. We show that the cross sections increase linearly with neutron number for these nuclei and discuss what this might imply.

An approach is proposed on the basis of which the experimentally known two lower energy eigenvalues of a Λ-particle, assumed to be bound in a hypernucleus by a central potential (from a fairly wide class of them), are able to provide in certain cases rather direct information on estimates of other useful quantities, such as the r.m.s. radii of the Λ orbitals, kinetic energies, etc.