Physics of Particles and Nuclei最新文献

This brief review is based on a lecture given by one of the authors at the international youth conference AYSS-2023. It is devoted to multimessenger astronomy, which studies astrophysical objects and phenomena using various particles and waves that bring information from space. The messengers include electromagnetic and gravitational waves, neutrinos, and cosmic rays. We discuss new opportunities that open up with the combined use of several carriers of information. Combination of data obtained through various observation channels allows one to obtain more complete and accurate information about the processes occurring in the Universe, and even to use it for studying fundamental physics.

An analytical method for finding the natural frequencies and eigenfunctions of transverse vibrations of a four-component fuel element (rod) for the designed NEPTUNE pulse reactor is proposed. As a model, a rod with a piecewise constant material density in the longitudinal direction is used. The frequency equation is explicitly obtained via Krylov functions, and the natural frequencies of the first eight modes are determined using a numerical and analytical method. To find higher modes, an exponential analytical extrapolation is proposed. Analytical expressions for eigenfunctions providing a good agreement with numerical calculations in the ANSYS environment are obtained.

The lecture at AYSS-2023 conference dedicated to the 110th birthday of Bruno Pontecorvo.

We analyse the (thermo)dynamics of the scalar degrees of freedom in the scalar boson stars through the dark matter density under extreme conditions. The boson stars are studied in terms of a dark scalar sector in such a way this sector couples to the standard model Higgs boson doublet plus gravity. The stability of the boson star is investigated at the level of the interaction between the scalars with the scale invariance breaking triggered by the electroweak symmetry breaking plus gravity. Analytic methods have been applied to an effective version of the theory, the scalar “tower” approximation, which should preserve an exact scale invariance. The production of the scalar dark matter and its decay have been discussed.

In this review, we outline the main features of the non-local gauge, named the contour gauge. The contour gauge belongs to the axial type of gauges and extends the local gauge used in the most of approaches. The geometry of gluon fields and the path-dependent formalism are the essential tools for the description of non-local gauges. The principle feature of the contour gauge is that there are no the residual gauges which are left in the finite domain of space. In the review, we present the useful correspondence between the contour gauge conception and the Hamiltonian (Lagrangian) formalism. The Hamiltonian formalism is turned out to be a very convenient framework for the understanding of contour gauges. The comprehensive comparison analysis of the local and non-local gauges advocates the advantage of the contour gauge use. As an example of practical worth, we consider the Drell–Yan process and discuss the gauge invariance of the corresponding hadron tensor. We show that the appropriate use the contour gauge leads to the existence of extra diagram contributions. These additional contributions, first, restore the gauge invariance of the hadron tensor and, second, give the important terms for the observable quantities. We also demonstrate the significant role of the additional diagrams to form the relevant contour in the Wilson path-ordered exponential. Ultimately, it leads to the spurious singularity fixing. Moreover, in the present review, we discuss in detail the problem of spin and orbital angular momentum separation. We show that in (SU(3)) gauge theories the gluon decomposition on the physical and pure gauge components has a strong mathematical evidence provided the contour gauge conception has been used. In addition, we prove that the contour gauge possesses the special kind of residual gauge that manifests at the boundary of space. Besides, the boundary field configurations can be associated with the pure gauge fields.

An effective field theory is constructed to describe low-energy processes in quantum electrodynamics—nonrelativistic quantum electrodynamics (NRQED). It is shown how the NRQED formalism makes it possible to develop a rigorous perturbation theory for calculating higher-order corrections in parameters (~{v mathord{left/ {vphantom {v c}} right. kern-0em} c}sim Zalpha ), (beta = {m mathord{left/ {vphantom {m M}} right. kern-0em} M}), where (v) is the speed of electrons (muons) in atoms, and ({m mathord{left/ {vphantom {m M}} right. kern-0em} M}) is the ratio of masses of light particles to those of heavy ones in a molecular system. As an example, the leading radiation correction of order (malpha {{(Zalpha )}^{4}}) is calculated. It is shown how the regularization parameter introduced into NRQED cancels in the final expression for the energy without leading to meaningless infinite results.

The SPD NICA is planned to operate as a universal facility for study of the unpolarized and polarized transverse momentum dependent (TMD) gluon distribution functions (PDF) of a nucleon using various hard probes. The first one is the charmonium production processes. The experiment aims to provide access to the gluon TMD PDFs, like the Sivers function and the Boer–Mulders function of a proton. In this article, we present an overview of theoretical predictions for ({J mathord{left/ {vphantom {J psi }} right. kern-0em} psi }), ({{chi }_{c}}), and ({{eta }_{c}}) production in the unpolarized and polarized (pp)-collisions at the (sqrt s = 27) GeV. We use the TMD parton model as it is postulated in the generalized parton model (GPM) and two models for (cbar {c})-pair hadronization into a final charmonium, namely the nonrelativistic QCD (NRQCD) and the Improved Color Evaporation Model (ICEM).

An up-to-date compilation of the world data on the ({{e}^{ + }}{{e}^{ - }} to {text{hadrons}}) total cross section is used for dispersive evaluation of the leading order hadronic contribution to the muon anomalous magnetic moment ({{a}_{mu }} = {{({{g}_{mu }} - 2)} mathord{left/ {vphantom {{({{g}_{mu }} - 2)} 2}} right. kern-0em} 2}). An impact of the recent (sigma ({{e}^{ + }}{{e}^{ - }} to {{pi }^{ + }}{{pi }^{ - }})) measurement by the CMD-3 experiment being in a significant tension with comparably precisise BaBar and KLOE measurements is discussed. Our value (a_{mu }^{{{text{had}}{text{,LO}}}} = (696.2 pm {{1.9}_{{{{e}^{ + }}{{e}^{ - }}{text{exp}}{text{.}}}}} pm {{2.1}_{{{text{syst}}{text{.}}}}}) times {{10}^{{ - 10}}}) is still consistent with recent estimates by other authors made before publication of the CMD-3 result. The SM prediction of ({{a}_{mu }}) including our (a_{mu }^{{{text{had}}{text{,LO}}}}) estimate (a_{mu }^{{{text{SM}}}} = 11 659 184(4) times {{10}^{{ - 10}}}) is by ( sim {kern 1pt} 4.7sigma ) lower than the experimental value (a_{mu }^{{{text{exp}}}} = 11 659 205.9(2.2) times {{10}^{{ - 10}}}).