Physics of Atomic Nuclei最新文献

A self-consistent method for studying second-order anharmonic effects on the basis of many-body quantum field theory is applied for the first time in calculating probabilities for (E)1 transitions between the ground state and the ([3_{1}^{-}times 2_{1}^{+}]_{1^{-}}) two-phonon state in the semimagic tin isotopes ({}^{104-124})Sn. The approach used involves taking into account (i) self-consistency of the nuclear mean field and effective interaction on the basis of the energy density functional method with the parameters of the Fayans functional DF3-a, which were earlier found to provide good results; (ii) ground-state three-quasiparticle correlations; and (iii) nuclear-polarizablility effects. Good agreement with available experimental data, including those for ({}^{112})Sn, is obtained. Values of (B)((E)1) are predicted for ({}^{104{-}110,114})Sn even–even nuclei. It is shown that dynamical ground-state three-quasiparticle correlations make a substantial contribution to the reduced probabilities for the (E)1 transitions in question, so that their inclusion is necessary for explaining experimental data.

The main goal of the SPASCHARM experiment is the systematic study of spin phenomena at intermediate energies. For this purpose, it is planned to create a beam of polarized protons and antiprotons. The research includes, among other things, the study of elastic scattering. Some of the required equipment for polarimetry is planned to be also used to study elastic scattering immediately after the creation of such a channel. In this work, a set of observables necessary for model-free reconstruction of elastic proton–proton scattering amplitudes is investigated and determined.

The work proposes a new method for measuring the gluon jet fraction in jet sample produced at the hadron collider. This method uses model quark/gluon templates—distributions of quark and gluon jets over the jet macro parameter. Within the framework of this method, it is possible to find a model uncertainty of measurement associated with the deviation of model quark/gluon templates from the true ones. The issue of data-motivated corrections to the model quark/gluon templates is discussed.

The development of reactor technologies and neutrino physics by means of nuclear reactors requires unceasingly refining and extending knowledge of reactors as an antineutrino source. By employing new data on the reactor-antineutrino spectrum and updated nuclear databases and upon taking into account special features of fuel burnup, the thermal energy released in the reactor core per fission event is calculated for a standard operating period of a thermal-neutron reactor.

The status of (z)-scaling theory is briefly reviewed. Basic physical principles of self-similarity, locality, and fractality are discussed. The microscopic scenario of interactions of hadrons and nuclei at a constituent level in terms of dimensionless variables is studied. Applicability of the (z)-scaling approach for the description of polarization processes is justified. A conservation law for new quantity—fractal cumulativity—is formulated. The statistical properties and crossing symmetry of fractal dimensions are investigated.

Below, we present a brief review of the recent studies of the polarized Bjorken sum rule (Gamma_{1}^{p-n}left(Q^{2}right)) for small values of (Q^{2}). Our careful analysis reveals an excellent agreement between the experimental data and the predictions recently obtained in the framework of analytic QCD. Well-known perturbative expressions for coupling constant on the contrary lead to a strong difference between these data and turn out to be inapplicable. To estimate calculated phenomenological values, we discussed the photoproduction limit.

We present a theoretical and computational study of positron supercritical resonances in systems consisting of two highly-charged bare nuclei. The resonance positions and widths depending on the internuclear separation are calculated with the help of the complex-scaling generalized pseudospectral method in modified prolate spheroidal coordinates. The results are applied to estimate the probability of spontaneous positron creation in slow U({}^{92+})–U({}^{92+}) and Cm({}^{96+})–Cm({}^{96+}) collisions.

The method of finding the values of asymptotic normalization coefficients (ANC) is proposed based on the analytic continuation of the (R)-matrix that describes the elastic nuclear scattering into the unphysical region of the negative energy of collision ((E<0)). The formula is derived, expressing the partial-wave scattering amplitude through the (R)-matrix and modified Coulomb functions. This formula allows, when continuing the amplitude to the region (E<0), to overcome difficulties associated with irregular behavior of the scattering amplitude near (E=0) if the Coulomb interaction is present. The proposed method is used to determine the ANC for the channel ({}^{16}textrm{O}toalpha+{}^{12})C.

The research of the electron and positron spectrum of galactic cosmic rays is an important task of high-energy astrophysics. The necessity of using new methods of electron and positron registration is caused by insufficient statistical reliability of data from modern experiments in the TeV energy range. In the present work, one of the possible registration methods based on the use of synchrotron radiation of electrons and positrons in the Earth’s magnetic field is investigated. Using modeling of trajectories of high-energy electrons, positrons, and synchrotrons photons emitted by them, the detector count rate for the ISS and ROS orbits has been estimated. The possibility of separation of electrons and positrons using this method is shown.

Collisions of cosmic ray particles with ultrahigh initial energies with nuclei in the atmosphere open a wide room for appearing of the novel dynamical features for multiparticle production processes. In particular, the laser-like behavior of pions driven by Bose–Einstein condensation would result in the shift to larger multiplicities and, as a consequence, could provide, in general, the enhanced yield of cosmic muons. In the present work the critical value of the space charged particle density for onset of Bose–Einstein condensation of the boson (pion) wave packets into the same wave-packet state is estimated within the model with complete multiparticle symmetrization for the energy domain corresponding to the ultrahigh energy cosmic rays (UHECR). Energy dependence of mean density of charged pions is evaluated for the cases of absence of the Bose–Einstein effects and for presence of laser-like behavior of pions. The possible influence of the Bose–Einstein condensation is discussed for the muon production in UHECR particle collisions with the atmosphere.