Searcharxiv⌕ Search

arXiv subjects

A. A. Zaitsev

Publications and source records attributed to A. A. Zaitsev.

At least 19 recordsLinked to original sources
arXiv2026

Threshold resonances in relativistic $^{16}$O and $^{22}$Ne dissociation

The nuclear emulsion method is applied to study binary dissociation leading to the formation of $α$-particles from $^{16}$O nuclei at 3.65 GeV per nucleon and $^{22}$Ne nuclei at 3.22 GeV per nucleon. The invariant mass distribution for the $^{16}$O$\to$$^{12}$C(0$^+_1$)+$α$ channel indicates decays of the $^{16}$O(0$^+_6$) excitation, whose probability exceeds the estimate for the $^{12}$C(0$^+_2$)+$α$ channel by a factor of 20. The invariant mass distribution for $^{22}$Ne$\to$$^{18}$O+$α$ exhibits a peak corresponding to $^{22}$Ne excitations around 11.6 MeV.

nucl-ex↗
arXiv2026

Isospin-symmetry in $pp$ and $AA$ collisions

The hypothesis of a violation of isospin-symmetry in pp and AA collisions is discussed. We show that the ratio of charged-to-neutral kaon cross sections, $R_K~=~\frac{σ_{K^+}+σ_{K^-}}{2σ_{K^0_S}}$, calculated within the similarity approach, including the gluon transverse momentum dependence (TMD) at low QCD scales, and using the Lund model in the form of the MC generator PYTHIA, is above 1 at energies $\sqrt{s}$ up to 20 GeV, even in the case of isospin-symmetry conservation. It decreases to 1, when the energy rises to a few TeV (ALICE data). The reason for this is related to the dynamics of kaon production. This energy behavior of $R_K$ does practically not depend on the sort of beam or target.

hep-ph↗
arXiv2026

The $^{8}$Be nucleus and the Hoyle state in dissociation of relativistic nuclei

The possibility of recording fragmentation events of relativistic nuclei in a nuclear emulsion, discovered back in the pioneering era of cosmic ray physics, opens up the prospect of using this method to study extremely cold ensembles of H and He nuclei in the interests of developing the physics of nuclear clustering and, possibly, expanding the scenarios of nuclear astrophysics. The results of the BECQUEREL experiment at JINR, obtained on unstable states in the relativistic dissociation of nuclei in a nuclear emulsion providing complete detection of fragments with record resolution are presented. According to the invariant masses calculated from the emission angles in the fragmentation cone, the decays of $^8$Be(0$^+$), $^8$Be(2$^+$), $^9$Be(1.7), $^9$B, $^6$Be, $^{12}$C(0$^+_2$) or the Hoyle state and $^{12}$C(3$^-$) have been identified. The contribution of $^8$Be(0$^+$), $^9$B and $^{12}$C(0$^+_2$) increases rapidly with the $α$-particle multiplicity. Their structure and the diversity of parent nuclei suggest the fusion of the latter. The usage of automated microscopy for an analysis of exposures at the JINR NICA accelerator complex becomes a modern basis to apply the nuclear emulsion method.

nucl-ex↗
arXiv2025

SiPM-based photodetectors for spectroscopic measurements in wide dynamic range

The results of measurements of the characteristics of photodetectors based on large-area SiPM matrices with a wide dynamic range are presented. The potential application of SiPM-based photodetectors for electromagnetic calorimetry in the energy range from hundreds of keV to tens of GeV is explored. The potential application of SiPM in gamma-spectroscopy is also discussed.

physics.ins-det↗
arXiv2025

Current problems of studying relativistic dissociation of light nuclei in nuclear emulsion

The progress of the study of unstable states in relativistic dissociation events of light nuclei in nuclear emulsion is presented. Identification of these states is possible by means of the invariant mass determined from the most accurate and complete measurements of relativistic fragment emission angles in the approximation of conservation of momentum per nucleon of the parent nucleus. It is established that excitations $^{12}\mathrm{C}(0^{+}_{2})$ and $^{12}\mathrm{C}(3^{-})$ lead in the dissociation $^{12}\mathrm{C} \rightarrow 3α$ and $^{16}\mathrm{O} \rightarrow 4α$. The contribution of $^{9}\mathrm{B}$ and $^{12}\mathrm{C}(0^{+}_{2})$ decays to the leading channel of $^{3}\mathrm{HeH}$ dissociation of the $^{14}\mathrm{N}$ nucleus is estimated. The motivation and the beginning of the analysis of the relativistic dissociation $^{16}\mathrm{O}$$\rightarrow$$^{12}\mathrm{C}α$ are presented. The presented relativistic dissociation events at the $^{7}\mathrm{Be}$$\rightarrow$$^{6}\mathrm{Li}p$ and $^{11}\mathrm{C}$$\rightarrow$$ ^{7}\mathrm{Be}α$ coupling threshold point to the prospect of moving beyond $α$-particle clustering.

nucl-ex↗
arXiv2024

On formation of the $^{12}$C(0$^+_2$) and $^{12}$C(3$^-$) states in relativistic dissociation of light nuclei

The formation of the excited states $^{12}$C(0$^+_2$) and $^{12}$C(3$^-$) is investigated in the dissociation of $^{12}$C $\to$ 3$α$ and $^{16}$O $\to$ 4$α$ at the energy of 3.65 GeV per nucleon in the nuclear emulsion. The identification becomes possible by reconstructing the invariant mass from measurements of emission angles in the approximation of conservation of momentum per nucleon of the parent nucleus. The contribution of the decays $^{12}$C(0$^+_2$) and $^{12}$C(3$^-$) to the dissociation $^{12}$C $\to$ 3$α$ is 11 and 19%, and in $^{16}$O $\to$ 4$α$ it is - 20 and 30%, correspondingly.

nucl-ex↗
arXiv2024

Study of the Involvement of $^8$Be and $^9$B Nuclei in the Dissociation of Relativistic $^{10}$C, $^{10}$B, and $^{12}$C Nuclei

The results obtained by estimating the contribution of $^8$Be and $^9$B nuclei to the coherent dissociation of $^{10}$C, $^{10}$B, and $^{12}$C relativistic nuclei in nuclear track emulsions (``white'' stars) are presented. The selection of ``white'' stars accompanied by $^9$B leads to a distinct peak appearing in the distribution of the excitation energy of 2$α$2$p$ ensembles and having a maximum at 4.1 $\pm$ 0.3 MeV. A $^8$Be nucleus manifests itself in the coherent-dissociation reaction $^{10}$B $\to$ 2He + H with a probability of (25 $\pm$ 5)\%, (14 $\pm$ 3)\% of it being due to $^9$B decays. The ratio of the branching fractions of the $^9$B + $n$ and $^9$Be + $p$ mirror channels is estimated at 6 $\pm$ 1. An analysis of the relativistic dissociation of $^{12}$C nuclei in a nuclear track emulsion revealed nine 3$α$ events corresponding to the Hoyle state.

nucl-ex↗
arXiv2024

Dissociation of Relativistic $^{10}$B Nuclei in Nuclear Track Emulsion

The structural features of $^{10}$B are studied by analyzing the dissociation of nuclei of this isotope at an energy of 1 A GeV in nuclear track emulsion. The fraction of the $^{10}$B $\to$ 2He + H channel in the charge state distribution of fragments is 78\%. It was determined based on the measurements of fragment emission angles that unstable $^{8}$Be$_{g.s.}$ nuclei appear with a probability of (26 $\pm$ 4)\%, and (14 $\pm$ 3)\% of them are produced in decays of an unstable $^9$B$_{g.s.}$ nucleus. The Be + H channel was suppressed to approximately 1\%.

nucl-ex↗
arXiv2024

Highlights of Unstable States in Relativistic Dissociation of Light Nuclei in Nuclear Emulsion

The results of the study of unstable states in relativistic dissociation of isotopes $^{9,7}$Be, $^{10}$B, $^{12,11,10}$C, $^{14}$N and $^{16}$O in nuclear emulsion have been summarized. Their decays are identified in distributions by invariant masses determined by fragment emission angles in the velocity conservation approximation. The observed diversity enables us to assume universality in the formation of nuclear-molecular states near the bond thresholds as a consequence of coalescence of emerging $α$-particles and nucleons.

nucl-ex↗
arXiv2024

Production of charged kaons in $Ar Sc$ collisions

Inclusive spectra of the kaons produced in $Ar Sc$ collisions as functions of their transverse momentum $p_T$ at mid-rapidity have been calculated within the approach based on the assumption of the similarity of inclusive spectra of the hadrons produced in nucleus-nucleus collisions at their small transverse momenta in the mid-rapidity region taking into account the quark-gluon dynamics in nucleon-nucleon interactions. This article gives a satisfactory description of NA61/SHINE data on $p_T$-spectra of the $K^\pm$ mesons produced in $ArSc$ collisions at the mid-rapdity ($y\simeq$ 0).

hep-ph↗
arXiv2024

From the first observations of cosmic rays to the physics of relativistic nuclei

Research of cosmic rays at the Physical Institute of the USSR Academy of Sciences resulted in the construction of the JINR Synchrophasotron. For this purpose the Electrophysical Laboratory of the USSR Academy of Sciences was founded in 1953, which became part of JINR in 1956 as the High Energy Laboratory. The initial milestones to develop experiments at the Laboratory on the Synchrophasotron are presented. Leaders and key participants in the experiments are highlighted, as well as the lessons and results relevant today.

physics.hist-ph↗
arXiv2023

Brief review on unstable states in dissociation of relativistic nuclei

The article presents a review of studying unstable states in the relativistic dissociation of nuclei $^{10}$B, $^{11,12}$C, $^{16}$O, $^{22}$Ne, $^{28}$Si, $^{84}$Kr and $^{197}$Au in the energy range from hundreds of MeV/nucleon to several tens of GeV/nucleon using the nuclear track emulsion method. A systematic study of the fragmentation of incident nuclei with multiple formation of the lightest fragments of He and H. This made it possible to study the dynamics of unstable nuclear states of $^8$Be, the Hoyle state and the 4$α$-particle state of the $^{16}$O nucleus above the threshold in the relativistic dissociation of nuclei due to precision measurements of fragment emission angles. It is shown that to reconstruct the relativistic decays of unstable nuclei in a nuclear track 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 allows one to search for more complex nuclear states. An indication has been obtained of growing probability to detect $^8$Be with increasing the number of relativistic $α$ particles in the event.

nucl-ex↗
arXiv2023

Cosmophysical aspects of relativistic nuclear fragmentation

The status of the study of multiple fragmentation of 950 MeV per nucleon Kr nuclei in a nuclear track emulsion aimed at determining the contributions of 2$α$ decays of $^{8}$Be, the Hoyle 3$α$ state, and the search for a 4$α$ particle condensate state, is presented. In events with the production of few relativistic fragments of He and H, the possibility of estimating the multiplicity of neutrons in the fragmentation cone of a projectile nucleus is studied. For the planar component of neutron transverse momenta estimated from the angles of observed secondary stars, the Rayleigh distribution parameter was 35 $\pm$ 7 MeV/$c$. The importance of such events for the interpretation of cosmophysical observations is noted.

nucl-ex↗
arXiv2022

An enhancement of formation of unstable $^{8}$Be nucleus with the growth of $α$-particle multiplicity in fragmentation of relativistic nuclei

In this paper, the correlation between the formation of the unstable $^{8}$Be nucleus and accompanying $α$ particles in the fragmentation of relativistic $^{16}$O, $^{22}$Ne, $^{28}$Si, and $^{197}$Au nuclei in a nuclear track emulsion is investigated. The $^{8}$Be decays are identified in a wide energy range by invariant masses calculated from 2$α$-pair opening angles. The adopted approximations are verified by data on fragmentation of $^{16}$O nuclei in a hydrogen bubble chamber in a magnetic field. An increase in the $^{8}$Be contribution to the dissociation with the growth of $α$-particle multiplicity is found.

nucl-ex↗
arXiv2022

Prospects of searching for unstable nucleus states in relativistic nuclear fragmentation

The article is dedicated to the experimental study in the relativistic approach to the problems of nuclear cluster physics for the prospects of the \href{http://becquerel.jinr.ru/}{BECQUEREL} experiment. The nuclear emulsion method applied in this experiment makes it possible to study thoroughly the relativistic final states in the fragmentation of nuclei. The focus of the presented research is the dynamics of emergence of the $^{8}$Be nucleus and the Hoyle state, as well as the search for the 4$α$-particle condensate decaying via the above nuclear states. In this context, the analysis of exposure to $^{84}$Kr nuclei at 950 MeV/nucleon is shown. As a continuation of the study of light nuclei, we have demonstrated the search for the isobar-analogue state of the $ ^{13} $N nucleus in the fragmentation of $ ^{14} $N nuclei at 2 GeV/nucleon.

nucl-ex↗
arXiv2022

Ratio of kaon-to-pion production cross-sections in $Be Be$ collisions as a function of $\sqrt{s}$

The inclusive spectra of pions and kaons produced in $Be Be$ collisions as functions of their transverse momentum $p_t$ at mid-rapidity are calculated within the self-similarity approach. A satisfactory description of NA61/SHINE data on these spectra and the ratio of $K^\pm$ to $π^\pm$ meson production cross sections in $Be Be$ collisions as a function of $\sqrt{s}$ are presented. The similarity of these observables to the ones for $pp$ collisions at mid-rapidity and in the wide range of initial energies is illustrated.

hep-ph↗
arXiv2022

The yield ratio of anti-nuclei and nuclei of relativistic nuclear collisions in the central rapidity region

This article describes calculations of the yield ratio of anti-particles to the yield of particles ($\bar{p}/p$, $\bar{d}/d$,$\overline{^{3}\mathrm{He}}$/$^{3}$He) in proton-proton and nuclear-nuclear interactions using the self-similarity parameter in the central rapidity region. The used approach is based on the study of relativistic nuclear interactions in the four-velocity space. The results of the calculations are compared with the existing experimental data in a wide center-of-mass energy range ($SPS$, $RHIC$, $LHC$). Within this approach the inclusive spectra of pions and kaons and ratios of their yields in $pp$ collisions have been successfully described earlier.

nucl-th↗