R.Ya. Kezerashvili

Double-charge-exchange reactions of π-mesons on three- and four-particle nuclei

Abstract A microscopic theory of the double-charge-exchange reaction of pions on three- and four-particle nuclei using the hyperspherical formalism is developed. In this approach, the wave functions of the initial and final nuclear states represent the eigenfunctions of the same hamiltonian and they are obtained using the same NN potentials. Non-linear differential equations for three and four particles in the continuum spectrum are obtained. The solution of these equations enables one to determine the wave functions, the asymptotic behaviour of which corresponds to the scattered wave. The meson current and two-step mechanisms of double-charge-exchange reactions are considered. The differential and total cross sections are calculated using various NN potentials. It is shown that the cross section is very sensitive to the form of the NN potential. The interaction between all nucleons in the final states is very significant and changes the reaction cross section both qualitatively and quantitatively. A good convergence of the reaction cross section in the hypermoments of both initial and final states is demonstrated. The experimental data are described satisfactorily.

Turbulence in a Bose-Einstein condensate of dipolar excitons in coupled quantum wells

(Received 30 April 2012; revised manuscript received 26 June 2012; published 10 July 2012)The nonlinear dynamics of a Bose-Einstein condensate (BEC) of dipolar excitons trapped in an externalconfining potential in coupled quantum wells is analyzed. It is demonstrated that under typical experimentalconditions the dipolar exciton BEC can be described by a generalized Gross-Pitaevskii equation with the localinteraction between the excitons, which depends on the exciton distribution function. It is shown that, if thesystem is pumped at sufficiently high frequencies, a steady turbulent state can be formed.DOI: 10.1103/PhysRevB.86.045108 PACS number(s): 71

Baryons in the field correlator method: Effects of the running strong coupling

The ground and P-wave excited states of nnn, nns, and ssn baryons are studied in the framework of the field correlator method using the running strong coupling constant in the Coulomb-like part of the three-quark potential. The running coupling is calculated up to two loops in the background perturbation theory. The three-quark problem has been solved using the hyperspherical functions method. The masses of the Sand P-wave baryons are presented. Our approach reproduces and improves the previous results for the baryon masses obtained for the freezing value of the coupling constant. The string correction for the confinement potential of the orbitally excited baryons, which is the leading contribution of the proper inertia of the rotating strings, is estimated.

Photofission of 27Al nucleus in the quasi-deuteron region of photonuclear absorption

Quasi-monochromatic photon beams of 108 MeV Compton-edge energy produced in the ROKK-1M facility at the storage ring VEPP-4M (BINP, Novosibirsk) and makrofol sheets as fission track detectors were used to measure the photofission yield of 27 Al. The fission yield was found to be .160 55 /b. From this result and previously measured 27 Al photofission yield at79 MeV end-point energy with the LADON apparatus, the trends of fission cross section and fissility have been obtained in the incident photon energy range 40-110 MeV. The present results and data for other intermediate-mass nuclei obtained with the same methodology indicate an increase of fissility with decreasing Z 2 =A as predicted by the liquid drop model for fissioning

Quasi-α-particle mechanism of pion double charge exchange on light nuclei

A microscopic theory of π-meson double charge exchange (DCE) on light nuclei has been suggested and developed on the supposition that the corresponding elementary process proceeds by quasi-α-particle formation within the nucleus. Light nuclei consisting of both α-particles and α-particles and clusters of other kinds are considered. To describe the bound state of the quasi-α- particle and the continuum spectrum state of four identical nucleons, the four-body hyperspherical basis has been applied, while to obtain the wave functions of the centers of mass of the cluster relative motion we solve either the three-body Schrodinger equation (in the case of a three-body cluster configuration) or the two-body Schrodinger equation (in the case of a two-body cluster configuration). The reactions π± + 12C → π∓ + 4p(4n) + 2α, π− + 7Li → π+ + 4n + 3H, π± + 6Li → π∓ + 4p(4n) + n + p, π± + 6Li → π∓ + 4p(4n) + d are investigated. It is shown that the effect of the final-state interaction between the four nucleons emitted by the nucleus in the process of π-meson DCE is rather important. The available experimental data on the 7Li nucleus can be explained quite satisfactorily on the supposition that this nucleus has a two-body cluster structure, and, hence, the π-meson DCE process occurs only on the α-particle. The differential and total cross sections of the reactions under investigation calculated as functions of the incident pion energy are essentially different for different nucleon-nucleon potentials. Experimental study of DCE on α-particle nuclei is shown to be a timely problem.

Baryons in the Field Correlator Method

The ground and P‐wave excited states of nnn, nns and ssn baryons are studied in the framework of the field correlator method using the running strong coupling constant in the Coulomb‐like part of the three‐quark potential. The string correction for the confinement potential of the orbitally excited baryons, which is the leading contribution of the proper inertia of the rotating strings, is estimated.