Table of contents

We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino–nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton.

The event-mixing method is analysed for the study of the event-by-event K/π ratio distribution. It is shown that there exists some correlation between the kaon and pion multiplicities in the mixed events. The K/π ratio distributions in the mixed events for different sets of real events are shown. The dependence of the distributions on the mean K/π ratio, mean and variance of multiplicity distribution in the real events is investigated systematically. The effect of imperfect particle identification on the K/π ratio distribution in the mixed event is also considered.

A complete set of formulae in terms of the moment-operator expansion is presented for the two-meson, two-photon and fermion–antifermion states that can be used in the analysis of scalar (S) and pseudoscalar (P) meson production in p and γγ collisions: p → SS, PP, SP and γγ → SS, PP, SP. The method of generalization of the formulae for the amplitudes of multi-meson production in the two-stage processes: of the type (spin-j) resonance + meson → three mesons is also discussed.

In the framework of non-relativistic Glauber theory with the quark model, the time-ordering of quark multi-scattering processes in hadron–proton elastic scattering at FNAL and CERN-ISR ranges of energy is considered. The time-ordering effect in the Glauber approximation with the geometrical scaling property of hadron reactions is presented. The phase variation effect, as suggested by Franco, is also discussed. A cloud effect is taken into account to obtain a good fit with the experimental data of elastic scattering differential cross section in the forward direction. The results obtained for proton–proton scattering at 200, 290, 500, 1070 and 1500 GeV/c lead us to neglect the phase variation effect in this range of energy. At the same time, the time-ordering of quark multi-scattering processes plays an important role in obtaining a good fit in the range of momentum transferred squared where q² > 3.5 (GeV/c)². In the case of π⁻-proton elastic scattering at 200 GeV/c, where the phase variation leads to a good fit with the experimental data, the sensitivity with respect to the time-ordering effect can be observed for q² > 6 (GeV/c)².

In conventional nuclear experiments a beam of accelerated nuclei collides with a target nucleus that is surrounded by other nuclei in a molecule, in condensed matter, or in a plasma environment. It is shown that for low collision energies possible nuclear reactions (including deuterium fusion) are strongly boosted by the environment. The gain is due to the transfer of centre-of-mass energy into energy of relative motion. The effect originates from a chain of preliminary three elastic collisions which transform the projectile–target experiment into one with colliding beams. Firstly, the projectile–target pair of nuclei undergo elastic scattering in which the projectile shares its energy and momentum with the target nucleus. Then the projectile and target nuclei collide with different heavy nuclei from the environment. These latter collisions change the velocities of the target and projectile nuclei and set them again on the collision course. Finally, the same pair of nuclei collide inelastically, this time giving rise to the nuclear reaction. The increased energy of the target nucleus increases the relative velocity up to √2 times, resulting in a drastic exponential increase of the probability to penetrate the Coulomb barrier and thereby sharply increasing the likelihood of the nuclear reaction. Applications to laser-induced fusion are discussed.

We derive the equation of state (EOS) for electrically charged neutral dense matter using the quantum hadrodynamics (QHD) model. This is carried out in a non-perturbative manner including quantum corrections for baryons through a realignment of vacuum with baryon–antibaryon condensates. This yields the results of relativistic Hartree approximation of summing over baryonic tadpole diagrams. The quantum corrections from the scalar meson is also taken into account in a similar way. This leads to a softening of the EOS for the hyperonic matter. The formalism also allows us to make a self-consistent calculation of the in-medium sigma meson mass. The effects of such quantum corrections on the composition of charged neutral dense matter is considered. The effect of the resulting EOS on the structure of neutron stars is also studied.

The proton-inelastic scattering from ^6,8He and ^7,11Li nuclei is studied in a folding model approach. A finite-range, momentum, density and isospin dependent nucleon–nucleon interaction is folded with realistic density distributions of the above nuclei. The renormalization factors N_R and N_I on the real and volume imaginary part of the folded potentials are obtained by analysing the respective elastic scattering data and kept unaltered for the inelastic analysis at the same energy. The form factors are generated by taking derivatives of the folded potentials and therefore require renormalizations. The β values are extracted by fitting the p + ^6,8He, ^7,11Li inelastic scattering angular distributions. The present analysis of p + ⁸He inelastic scattering to the 3.57 MeV excited state, confirms L = 2 transition. Similar analysis of the p + ⁶He inelastic scattering angular distribution leading to the 1.8 MeV (L = 2) excited state fails to satisfactorily reproduce the data.

In the U(1)_N extension of the supersymmetric standard model with E₆ particle content, the heavy singlet superfield N may decay into a quark and a diquark as well as an antiquark and an antidiquark, thus creating a baryon asymmetry of the Universe. We show how the three doublet and two singlet neutrinos in this model acquire mass from physics at the TeV scale without the benefit of using N as a heavy right-handed neutrino. Specifically, the active neutrinos get masses via the bilinear term μLX^c which conserves R-parity, and via the nonzero masses of the sterile neutrinos. The existence of the latter may be probed via their branching fraction from Z' decay. The neutrino mass matrix may be (partially) reconstructed from the decays of the predicted new lepton doublets X and X^c.

Analytical treatment of skyrmions given by rational map (RM) ansatz proposed recently for the Skyrme model is extended for the model including the sixth-order term in chiral field derivatives in the Lagrangian and used for calculations of different properties of multiskyrmions. At large baryon numbers the approximate solutions obtained are similar to the domain wall, or spherical bubbles with energy and baryon number density concentrated at their boundary. A rigorous upper bound is obtained for the masses of RM multiskyrmions which are close to known masses, especially at large B. For the sixth-order variant the lower bound for the masses of RM skyrmions is obtained as well. The main properties of the bubbles of matter are obtained for an arbitrary number of flavours. They are qualitatively the same for the fourth- and sixth-order terms present in the Lagrangian, although differ in some details.

The influence of low-lying discrete nuclear states on isotopic abundances in presupernova cores, is discussed. Assuming the hypothesis of nuclear statistical equilibrium (NSE), the Saha equation has been solved for a set of 65 nuclear species (including free protons and neutrons). Experimental data have been used in the calculation of the first terms of the nuclear partition function. The obtained abundances are compared with those evaluated using an energy level density in the computation of the nuclear partition function. We conclude that in future calculations involving isotopic abundances in presupernova cores, the low-lying nuclear states need to be treated as discrete ones when experimental data are available.

Based on the bound state description of the muon and general relativistic covariant quantum field theory, we illustrate with a simple composite model that the observed deviation of (g − 2)_μ can be a demonstration of the substructure of the muon and give the constraints on the radius of the muon in different cases of light constituents and heavy constituents.

The medium modification of vector meson masses is studied taking into account the quantum correction effects for the hot and dense hadronic matter. In the framework of quantum hadrodynamics (QHD), the quantum corrections from the baryon and scalar meson sectors were earlier computed using a nonperturbative variational approach through a realignment of the ground state with baryon–antibaryon and sigma meson condensates. The effect of such corrections was seen to lead to a softer equation of state and an increase in the in-medium baryonic masses as compared to when such quantum effects are not taken into account. The ω and ρ-meson masses in hot nuclear matter, as well as the masses for ω and ϕ vector mesons in hyperon-rich matter are studied in the present work, taking into account such quantum effects. It is seen that the strange vector meson (ϕ) mass has a smaller medium modification than the ω meson in the strange hadronic matter. The quantum corrections arising from the scalar meson sector result in an increase in the masses of the vector mesons in the hot and dense matter, as compared to the situation when only the vacuum polarization effects from the baryonic sector are taken into account.

We investigated the electroweak corrections from one-loop diagrams involving the third generation (s)quarks to the decay width of the process ₁⁺ → W⁺₁⁰ in the framework of the minimal supersymmetric standard model. Our calculation shows that these corrections are not very sensitive to the mass of the lightest neutralino ₁⁰ and the sbottom mixing angle θ_b, but depend strongly on the top squark mixing angle θ_t and tanβ. With our chosen parameters, we find that these radiative corrections can exceed 10%, therefore they should be taken into account for the precise experimental measurement at future colliders.

We show that the remaining internal longitudinal flow of colliding quarks in nuclei offers a natural explanation for the diversity of rapidity spectral shapes observed in Pb–Pb 158A GeV nuclear collisions. Thus QGP sudden hadronization reaction picture is a suitable approach to explain the rapidity spectra of hadrons produced.

The Landau parameters of nuclear matter have been calculated in relativistic Hartree approximation as a function of a renormalization scale. The results have then been compared to the empirical values deduced from constraints on isoscalar compression modes, spin-orbit splitting in nuclei and energy dependence of the nucleon–nucleus optical potential. For comparison, the results obtained for relativistic non-linear models and Dirac–Brueckner–Hartree–Fock calculations are also shown.