Physics of Particles and Nuclei最新文献

A physical model based on the hypothesis of the existence of a photon superstar is considered. This model is shown to be capable of describing gravity and quantum phenomena from a unified position.

A brief overview of the development of theoretical approaches to describing the structure of heavy atomic nuclei is given. Both shell model and collective nuclear model are considered. Great attention is paid to the symmetries presented in these models. Approaches based on nucleon–nucleon interaction are discussed in detail.

A review of the results of research at the SSC RF-IPPE accelerator complex, conducted to study the phenomenon of delayed neutron (DN) emission in the fission of heavy nuclei by neutrons, is presented. Experimental data on the macroscopic DN characteristics are considered, which are of paramount importance for safe operation of nuclear reactors: the total DN yield and the DN time parameters (relative yields of DN and half-lives of their precursors), the integral DN energy spectra for the ²³⁵U fission by thermal neutrons and the DN 8-group spectra obtained on their basis. The procedure for the estimation of the DN time parameters and their covariance matrices are considered. The data obtained are compared with the data obtained by other authors. This review does not include the works of the authors devoted to developed physical methods for studying the physics of fission of heavy nuclei by neutrons based on detecting delayed neutrons, as well as works related to the physical interpretation of the results obtained. Only a brief list of them is provided with appropriate references.

An overview of the results obtained within the framework of the JINR-UNISA collaboration in the field of theoretical study of of Josephson nanostructures is presented. In particular, our work has involved studies of a wide variety of nonlinear dynamic effects in various systems of coupled Josephson junctions, including superconductor/ferromagnet/superconductor junctions, which are currently being investigated intensively due to the potential applications is superconducting spintronics.

Within the conserving Φ-derivable and virial approaches to equilibrium dilute strongly-interacting systems we study a system of non-relativistic fermions of one kind (e.g., neutron matter) interacting via a pair potential in the limit (n{{lambda }^{3}} ll 1), where n is the fermion number density and λ is the thermal wavelength. The variety of potentials of the quantum and classical origin is used for the quantitative comparison of results obtained within both approaches. In all cases relevant to the nucleon-nucleon interaction, the attraction volume of the interaction is larger than the repulsion one. General properties of the Φ derivable approach are studied. Expressions for the second and third virial coefficients are derived and analyzed for the Φ functional including the tadpole and sandwich diagrams. The classical high-temperature limit of the Φ functional is reproduced by the tadpole diagram. Next, classical, semiclassical (up to order ({{hbar }^{3}})), and purely quantum (Beth-Uhlenbeck) virial expansions of the equation of state are studied. Various extrapolations of the virial equation of state are considered including the van der Waals form and the excluded volume models. We derive the expression for the second virial coefficient within the effective range approximation for the scattering amplitude. Comparison with purely quantum Beth–Uhlenbeck result employing experimental phase shifts shows approximate agreement for low temperatures, (T lesssim 20) MeV. Then, we study the problem of the anomalously large empirical value of the nucleon-nucleon scattering length, appearing due to existence of the quasi-bound state in nucleon-nucleon scattering. The latter is destroyed already in a dilute matter due to the Pauli blocking. Subtracting the quasi-bound state term, we show that the second virial coefficient has the same low temperature dependence as one obtained within the Φ derivable approach in the Born approximation. Also, we discuss origins of differences arising beyond the region of the common validity of the Φ derivable and virial approaches.

The review describes the results of experiments based on quite different and independent approaches to solving the problem of interaction of muons with nuclei. Different paths of muon capture by nuclei and subsequent paths of secondary processes are considered: radiationless capture followed by nuclear fission, excitation of the nucleus with the escape of particles (neutrons and charged ones), and excitation of nuclear levels with the escape of gamma quanta. The experimental data require refinement, in particular with respect to the spectroscopy of fission fragments, the spectroscopy of secondary particles, and statistical accuracy. All of the experimental methods described rely on interpretation within theoretical models. Improvement in each of these parts will mutually stimulate refinements or new paths in subsequent research. The article is addressed to young aspiring physicists interested in muon physics and looking for new phenomena of interactions of elementary particles with nuclei and atoms, and solutions to emerging problems using modern experimental methods.

Obtaining quality physics results requires high-statistics data with low background contamination. The task of maximizing the signal as well as accurate estimation of combinatorial background is especially important at the start-up of the experiment when the amount of data is rather limited. The Multi-Purpose Detector (MPD) experiment at the NICA collider will have to deal with such issues in its first run. In this article, the task of reconstructing lambda hyperons with their weak decay into a proton and a negative pion using Monte Carlo simulated event samples of heavy-ion collisions is considered. Two approaches for evaluating the combinatorial background in the invariant mass spectra of decay products are studied: like-sign pair combinations and event mixing. Background-subtracted and efficiency-corrected hyperon distributions are presented, demonstrating performance of the MPD experiment in the future collider run.

The article presents a review of the results of studies of the unstable states in the relativistic dissociation of nuclei ¹⁰B, ^11,12C, ¹⁶O, ²²Ne, ²⁸Si, ⁸⁴Kr, and ¹⁹⁷Au in the energy range from hundreds of MeV/nucleon to several tens of GeV/nucleon using the nuclear track method. A systematic study of the fragmentation of incident nuclei with multiple production of the lightest fragments of He and H made it possible to study the dynamics of the manifestation of unstable nuclear states of ⁸Be, the Hoyle state, and the 4α-particle state of the ¹⁶O nucleus above the threshold in the relativistic dissociation of nuclei thanks to precision measurements of fragment outgoing angles. It is shown that, to reconstruct the relativistic decays of unstable nuclei in a nuclear photographic emulsion, it is sufficient to determine the invariant mass of the system of He and H fragments in the approximation of conservation of momentum per nucleon of the parent nucleus. This approach makes it possible to search for more complex nuclear states. An indication was obtained of an increase in the probability of detecting ⁸Be with an increase in the number of relativistic α particles in the event.