Physics of Atomic Nuclei最新文献

The inhomogeneous structure of the interstellar medium (ISM) is characterized by large-scale fluctuations that significantly affect the cosmic ray propagation process. Accounting for this influence can only lead to adjustments in the diffusion process parameters but even to pass from differential operators to integral ones. The most crucial characteristics of a turbulent medium is its power spectrum. Including appropriate approximations of this spectrum allows considering this problem in the framework of the traditional diffusion approach [1, 2]. This article explores the analytical representations of this spectrum applied in the cosmic ray transfer theory, including the four-parameter Uchaikin–Zolotarev approximation, derived from the generalized Ornstein–Zernike equation. Testing of the latter revealed that, with carefully chosen parameters, it accurately replicates numerical modeling results both in the inertial interval and beyond. Therefore, it can be effectively employed in addressing cosmic ray transfer issues within a turbulent interstellar medium.

The paper analyzes the double-differential cross sections for the emission of cumulative protons, pions, kaons, and antiprotons in collisions of carbon nuclei on a fixed target at an energy of 19.6 GeV/nucleon obtained in the IHEP experiment at the U-70 accelerator (Institute for High Energy Physics, National Research Centre Kurchatov Institute). When describing these spectra, the nonequilibrium approach was taken into account as a result of the joint solution of the kinetic equation with the equations of hydrodynamics. Comparison with other approaches are made.

The 10 m({}^{2}) muon hodoscope made of drift tubes with length of 3.7 m and diameter of 52 mm is under development and construction at the NRC Kurchatov Institute—IHEP. In total, 768 drift tubes are grouped into six identical multilayers, each consisting of two tube layers with parallelly placed tubes. The orientation of tubes in adjacent multilayers is orthogonal; thus, the hodoscope has six (X) and six (Y) layers of tubes. The mechanical structure, on-chamber electronics, and data acquisition system are described. Expected technical characteristics and some test results are presented.

Regular measurements of radio emission produced by relativistic air shower particles were started at the Yakutsk array in 1986. After monitoring of the background noise in the array area, the frequency of 30–35 MHz was chosen, because noise level is minimal in this frequency range. During this time, air showers with highest energies of 100 EeV were registered. By means of hybrid measurements of charged particles, Cherenkov light and radio emission, it was shown that signal amplitude proportional to air shower energy and shape of lateral distribution at sea level correlates with the depth of maximum development. By these characteristics, the atomic weight of primary particles that generated air shower is estimated within QGSjetII-04 framework simulation.

During the SN1987A explosion on February 23, 1987, four underground neutrino detectors and two gravitational antennas in Rome and Maryland detected signals associated with the gravitational collapse of the star’s core. Because it is impossible to detect direct gravitational radiation from the collapse of SN1987A with antennas, it is still unclear what events were recorded by gravitational antennas. In this work, an amplitude analysis of the signals from gravitational antennas in Rome and Maryland in the vicinity of the signals from neutrino detectors during Supernova SN1987A was carried out. It is shown that the amplitude distributions in all antenna signals are consistent with the distribution of fluctuating energy losses of atmospheric muons crossing the antennas. A conclusion has been made about the muon origin of signals Weber type antennas, aluminized cylinders with a mass of 2–3 t.

In this work, a new analysis of the isotopic composition of boron nuclei (B) in galactic cosmic rays (GCRs) in the range of rigidities of 1–5 GV (nuclear energies 0.1–1.5 GeV/nucleon) was carried out using data from the PAMELA space experiment 2006–2014 on the rigidity of detected nuclei and their velocity (time-of-flight analysis and ionization losses in the instrument’s multilayer calorimeter). The new results of the PAMELA experiment expand the energy range of previous measurements, are consistent with the few existing data, and indicate deviations of the B isotope ratios from the GALPROP simulation data for the GCR, similar to the deviations for the Li and Be isotopes in the PAMELA data, which can be interpreted as evidence of observation against the background of the GCR of the contribution of several local sources from explosions of nearby (hundreds of parsecs) supernovae.

The evolution of neutron single-particle spectra of isotones with (N=32) and (34) new magic neutron numbers in the region (16leq Zleq 32) was calculated in the dispersive optical model. It was shown that the minimum of the difference between the Fermi energy and the half-sum of the energy levels of the last predominantly occupied state and the first predominately unoccupied state is achieved in the magic isotones with (N=32) and (34). The calculated root-mean-square radius of the neutron halo-like state (2p_{3/2}) in the double magic ({}^{52})Ca nucleus exceeded the radius of the underlying (1f_{7/2}) state by 0.8 fm. It is consistent with the recent experimental data and theoretical predictions that explain ‘‘unexpectedly’’ large root-mean-square charge radius of this nucleus.

The work is devoted to the transverse polarization ((P_{N})) of (Lambda)-hyperons and corresponding antihyperons produced in meson–proton and meson–nuclear interactions in inclusive reactions. The currently available experimental data are compared with calculations based on the chromomagnetic polarization of quark (CPQ) model. The main features of the CPQ model are the prediction of hyperon polarization oscillations depending on the Feynman variable (x_{F}) in the case of a sufficiently strong chomomagnetic field and resonant dependence of the polarization on the c.m. energy ((sqrt{s})) for some reactions. Calculations based on the CPQ model were performed for still unexplored kinematic regions and various targets and can be tested in the SPASCHARM experiment at the NRC ‘‘Kurchatov Institute’’—IHEP.

In the present study, a systematic analysis is made on ({}^{3})H and ({}^{3})He mirror nuclei. The elastic and inelastic scattering angular distributions of the ({}^{3})H and ({}^{3})He from ({}^{20})Ne and ({}^{24})Mg at 33 MeV are investigated within the double folding potential based on the Optical Model. The exchange effect related to nonlocality is taken into account in a form of a correction factor to the real potential and the resulted one is known as local equivalent double folding potential. The imaginary potential has taken to be Woods–Saxon volume shaped. The results are contrasted with each other as well as with the experimental data to give evidence about the importance of these studied items. Also, the reaction cross sections and nuclear deformation parameters are given.

The General Parton Distributions (GPDs) are applied to study the hard Pseudoscalar Meson Production (PMP) at high energies. The PMP amplitudes are be obtained within the GPDs factorization. They are expressed in terms of GPDs’ convolution functions, which are most essential in PMP reactions. We show that these convolution functions can be extracted from the PMP data in future EIC of China (EicC). Predictions of (pi^{0}) and (eta) production at typical EicC energies are performed.