Physics of Atomic Nuclei最新文献

The NOvA experiment is designed to study oscillations in an accelerator neutrino beam. Due to the large size and high segmentation of the detectors, as well as a flexible system of program triggers and data acquisition, atmospheric neutrinos can be detected and studied in the NOvA. This paper presents a developed methodology for atmospheric neutrino registration in the far detector: it outlines the procedure for selecting and reconstructing triggers, calculates their efficiency for background and signal events, and finally, provides the expected energy spectrum of atmospheric neutrinos.

We consider Axion-like particle (ALP) model to construct numerical spatially homogeneous anisotropic Kantowski–Sachs cosmological model. We investigate the impact of model’s parameters on the behavior of the scalar field. We demonstrate that axion-like scalar field could behave differently, having an equation of state parameter (EoS) (omega) in the interval (-1leqomegaleq 1).

The results of determining the neutron yield of the NS-21M facility, based on the I-2 linear proton accelerator and 3.8 mm thick Be target under bombardment by 21.5 MeV protons, are presented. This value was obtained by calculating the integral neutron flux passing through the front hemisphere at a specified distance from the center of the Be target relative to the average proton flux transmitted through a collimator of defined diameter. The experimental value of this quantity is (Y_{n}^{{textrm{exp}}}=(1.35pm 0.09)times 10^{-2}), while the calculated value (Y_{n}^{{textrm{calc}}}=1.18times 10^{-2}) was derived by simulating the full mathematical model of the NS-21M stand using the PHITS-3.31 transport code. For 21.2 MeV protons, reaction cross-sections of ({}^{textrm{nat}}textrm{Cu}(p,x){}^{61})Cu, ({}^{62})Cu, and ({}^{64})Cu were determined using the monitor reactions ({}^{textrm{nat}}textrm{Cu}(p,x){}^{62})Zn and ({}^{textrm{nat}}textrm{Cu}(p,x){}^{63})Zn. Simulated excitation functions for these reactions (TENDL-2023, JENDL-5, PADF-2, and PHITS-3.31 with the INCL model) were plotted over the 0.01–3 GeV range alongside experimental data from EXFOR.

Massive primordial black holes may have formed in the early universe, accounting for a small fraction of dark matter. Most of dark matter, however, may be composed of elementary particles or black holes with smaller masses. These objects could form dense spikes around the large black holes during the radiation-dominated phase of the universe’s evolution. Dark matter particles can annihilate in the spikes. In this study, we discuss the structure and properties of the spikes, considering their transformation due to annihilation. In the hybrid scenario involving black holes of various masses, small black holes can collide and merge in the central regions around larger black holes.

One of the features of general relativity is the possible existence of space-time with a nontrivial topological and casual global structure. The real three-dimensional space might in principle be multiply connected and there might exist wormholes in it. The presence of a wormhole leads to the appearance of corrections to the Coulomb law. In the present work, an exact solution of the Laplace equation for a flat space with a wormhole whose mouths are spheres is found. It is shown that a point charge is attracted to the wormhole at all points in space except for the plane of symmetry. An analogy is noted between the attraction of a charge to the mouth of a wormhole and the attraction of a charge to a polarizable body. A freely moving charge experiences acceleration due to the presence of attraction to the mouth of a wormhole, which leads to the appearance of electromagnetic radiation.

The formation of solitons (such as closed domain walls) in the super-Early Universe is predicted in a number of theories of the formation of primordial black holes. However, the interaction of particles of the surrounding medium with the solitons should affect their dynamics. In the paper, we consider the interaction between domain walls and scalar particles which can play a role of dark matter. It is shown that when the temperature of the scalar particle gas, caused by the expansion of the Universe, decreases below a certain threshold value, the wall abruptly becomes opaque and locks particles inside itself. We discuss the dynamics of a single domain wall taking into account pressure of scalar particles locked inside a closed wall. It is shown, this effect leads to a time delay of domain wall collapse and the deferred formation of primordial black holes.

The aim of the study is to create an optical module made of a wavelength shifting (WLS) plate, an acrylic plate with a wavelength shifting dopant, and a photomultiplier (PMT) that meets the requirements for usage in water Cherenkov detectors. Preliminary results of the characteristics of PMT for usage as an element of a module with WLS plate are presented and the optimal design of the plate is developed. The choice of WLS dopants and their concentrations, as well as types of reflectors, are based on the tests performed. An assessment of the wavelength shifting plates’ aging properties was also done.

We consider cosmological models based on the scalar-torsion gravity implying non-minimal coupling between torsion and the scalar field with certain relations between model’s parameters. Based on observational constraints on the values of the parameters of cosmological perturbations, the type of the coupling was determined. It was noted that any inflationary models constructed on the basis of the proposed approach can be verified by observational constraints.

The presented analysis aims at study of heavy neutrinos ((N)) with masses (m_{N}<493text{ MeV/}c^{2}). These particles can be produced in (K^{pm}) and (pi^{pm}) decays in the standard neutrino beam and then they subsequently decay in T2K’s near detector ND280. Considered heavy neutrino two- and three-body decay modes are (Nrightarrow l^{pm}_{alpha}pi^{mp}), (Nrightarrow l^{+}_{alpha}l^{-}_{beta}nu(overline{nu})), where ((alpha,beta=e,mu)). Search for these events is performed in Time Projection Chambers of ND280 in order to significantly reduce background from neutrino interactions. Usage of new tracking method in TPC among other reconstruction improvements, updated neutrino interaction model and additional statistics will allow to improve experiment sensitivity. Signal selection efficiencies and preliminary systematic uncertainties are shown.

In this work, we study neutrino spin oscillations in the case when they are gravitationally scattered off a rotating Kerr black hole surrounded by a thick magnetized accretion disk. We consider only toroidal magnetic field inside the disk. Neutrino spin precession is caused by the interaction of the neutrino magnetic moment with the magnetic field in the disk. Our treatment of spin oscillations of the observed neutrino fluxes, is based on numerical simulations of the propagation of a large number of incoming test neutrinos using High Performance Parallel Computing. We briefly discuss our results and their applications in the observations of astrophysical neutrinos.