International Journal of Modern Physics E

Recent experimental and theoretical advances in investigating electromagnetic meson production reactions in the nucleon resonance region are reviewed. We give a description of current experimental facilities with electron and photon beams and present a unified derivation of most of the phenomenological approaches being used to extract the resonance parameters from the data. The analyses of π and η production data and the resulting transition form factors for the Δ(1232)P₃₃, N(1535)S₁₁, N(1440)P₁₁, and N(1520)D₁₃ resonances are discussed in detail. The status of our understanding of the reactions with production of two pions, kaons, and vector mesons is also reviewed.

0ν2β decay is a very powerful tool for probing the physics beyond the particle Standard Model. After the recent discovery of neutrino flavor oscillation, we know that neutrinos must have a mass (at least two of them). The 0ν2β decay discovery could fix the neutrino mass scale and its nature (Majorana particle). The unique characteristics of the Borexino detector and its Counting Test Facility (CTF) can be employed for high sensitivity studies of ¹¹⁶Cd0ν2β decay: the CAMEO project. A first step foresees 24 enriched ¹¹⁶CdWO₄ crystals for a total mass of 65 kg in the Counting Test Facility; then, 370 enriched ¹¹⁶CdWO₄ crystals, for a total mass of 1 ton in the Borexino detector. Measurements of ¹¹⁶CdWO₄ crystals and Monte Carlo simulations have shown that the CAMEO experiment sensitivity will be , for the 65 kg phase, and for the 1 ton phase; consequently the limit on the effective neutrino mass will be ≤ 60 meV, and ≤ 20 meV, respectively. This work is based upon the experiments performed by the INR (Kiev) (and from 1998 also by the University of Florence) at the Solotvina Underground Laboratory (Ukraine). The current status of 0ν2β, and future projects of 0ν2β decay research are also briefly reviewed.

A new set of relativistic mean-field theory (RMFT) parameters, NL4, ensuring a better description of the average nuclear energy as given by the new Lublin–Strasbourg mass formula, is used in a self-consistent description of 171 spherical even-even nuclei at temperatures 0≤T≤4 MeV. Single-particle level densities for this sample of nuclei are determined by analyzing the data obtained for various temperatures. The average dependence of the single-particle level density on mass number A and isospin is given and compared with previous estimates obtained using the RMFT-NL3, Thomas–Fermi and semiclassical Skyrme SkM* approaches.

The antideuteron and antihelium-3 production rates in high-energy heavy-ion collisions are calculated in the framework of fusion mechanism. It is supposed that participating in the fusion are moving in the mean field of other fireball constituents. It is demonstrated that at high energies, where many pions are present in the fireball, the number of produced and is determined by the balance between created and disintegrated (mainly in collisions with pions) and . The explicit formulae for coalescence parameters are presented and compared with the data.

Self-affine multiplicity scaling is investigated in the framework of two-dimensional factorial moment methodology using the concept of the Hurst exponent (H) considering different bins of the phase space. We have investigated the fluctuation pattern of emitted pions in ²⁴Mg-AgBr interactions at 4.5 AGeV and this study reveals that the fluctuation is self-similar in some bins, whereas it is self-affine in other bins, that is, the multiplicity scaling is bin-dependent.

Polarization observables of the three charge states of the pion for the γd→πNN reaction with polarized photon beam and/or oriented deuteron target are evaluated over the whole Δ(1232)-resonance region adopting a nonrelativistic model based on time-ordered perturbation theory. Results for the π-meson spectra, linear photon asymmetry, vector and tensor target asymmetries are presented. Particular attention is given, for the first time, to double polarization asymmetries for which we present results for and . We find that all other double polarization asymmetries of photon and deuteron targets vanish.

The ground state properties of even mass Cr and Fe isotopes are studied using the generalized hybrid derivative coupling model. The energy surface of each isotope is plotted as a function of the mass quadrupole moment. The neutron numbers N=20 and N=40 are seen to remain magic numbers but N=28 and 50 are predicted to be non-magic. The neutron number N=70 turns out to be a magic number according to the present calculation. In all the isotopes studied the calculated binding energy values are less than those obtained from experiment while the deformation is in better agreement.

An exact expression using the projection operator method to extract widths and spectroscopic factors is derived. It is applied to sub-Coulomb resonances as they occur in α-decay. A number of α-decaying nuclei are investigated. The widths and spectroscopic factors extracted using the proposed expression are found to be in excellent agreement with those obtained by other methods. Earlier equations of the projection operator for widths and spectroscopic factors would give unrealistic results in this region.

Working within the framework of the Coulomb modified Glauber model and the optical limit approximation, we propose a phenomenological method of analysis for heavy-ion elastic scattering data at intermediate energies. Instead of using the commonly employed Gaussian approximation for the input NN amplitude that is deficient in some respects at low intermediate energies, we evaluate it in terms of a three parameter phenomenological NN phase shift function. The application of the method to some ¹²C-nucleus and ¹⁶O-nucleus systems shows that a very good description of the elastic scattering data at several energies can be obtained in this way. In particular, the ¹²C–¹²C elastic scattering data at 200 MeV/nucleon is very well reproduced. We also calculate the effective NN potential using the phenomenological NN phase shift function by the method of inversion. The calculated potential shows the expected behavior and is found to vary smoothly with energy.

We investigate one-neutron and two-neutron emission from ¹³²Sn and its neighboring isotopes due to thermal excitation. The rotational states of ¹³²Sn at different temperatures are investigated. The effects of separation energy and thermal excitation energy on neutron emission probability are studied.