Optical model potential analysis of n¯A and nA interactions

Abstract

We use a momentum-dependent optical model potential to analyze the annihilation cross sections of the antineutronn on C, Al, Fe, Cu, Ag, Sn, and Pb nuclei for projectile momenta p lab 500 MeV/c. We obtain a good description of annihilation cross section data of Barbina et al. [Nucl. Phys. A 612, 346 (1997)] and of Astrua et al. [Nucl. Phys. A 697, 209 (2002)] which exhibit an interesting dependence of the cross sections on p lab as well as on the target mass number A.We also obtain the neutron (n) non-elastic reaction cross sections for the same targets. Comparing the nA reaction cross sections σ nA rec to thenA annihilation cross sections σn A ann , we find that σn A ann is significantly larger than the σ nA rec , that is, the σn A ann /σ nA rec cross section ratio lies between the values of about 1.5 to 4.0 in the momentum region where comparison is possible. The dependence of then annihilation cross section on the projectile charge is also examined in comparison with the antiprotonp. Here we predict thepA annihilation cross section on the simplest assumption that bothpA andnA interactions have the same nuclear part of the optical potential but differs only in the electrostatic Coulomb interaction. Deviation from a such simple model extrapolation in measurements will provide new information on the difference betweennA andpA potentials. PACS numbers: 24.10.-i, 25.43.+t, 25.75.-q, 2

Pocket resonances in low-energy antineutrons reactions with nuclei

“…[3]) revealed that the annihilation cross sections of n, and p, on C nuclei at low energies, appear to follow a similar trend with only minor differences. Much curious about the puzzle, we recently introduced a new momentum-dependent optical potential to investigate the behavior of the annihilation cross-sections for the n, and the p, on C, Al, Fe, Cu, Ag, Sn, and Pb nuclei in the momentum range 50 − 500 MeV/c [26], via the ECIS code [27]. The calculated results were concordant with the OBELIX's annihilation cross-section data [16,17].…”

“…However, we shall follow a collection of WKB works for complex-potential scattering by Brink, Takigawa, Lee, Marty, and Ohkubo [37][38][39] as they deemed proper for the present analyses. We adapt the same momentum-dependent optical potential used in our earlier work [26] in the present semiclassical theory. We consider the concept of the interference between a barrier wave reflected at the potential barrier and modified by the tunneling effect, and an internal wave which penetrates the barrier, into the potential pocket, and reemerges through the barrier out to r → ∞.…”

“…which is complex and the values for the parameters r o , a o and volume terms V and W are listed in Table 1, 2 and 3 in [26]. To keep the analyses simple, we consider only the nuclear volume terms in the present semiclassical theory.…”

Theoretical analysis of antineutron-nucleus data needed for antineutron mirrors in neutron-antineutron oscillation experiments

“…Recently, Wong and Li proposed [89] a new manyparameter potential which describes well the existing experimental data on antinucleon-nucleus annihilation. No comparison with other energy level shifts and widths of atomic levels and differential elastic cross section was presented in the article.…”

Theoretical Analysis of Antineutron-Nucleus Data needed for Antineutron Mirrors in Neutron-Antineutron Oscillation Experiments

“…Recently, Wong and Li proposed [89] a new many parameter potential which describes well the existing experimental data on antinucleon-nucleus annihilation. No comparison with other energy level shifts and widths of atomic levels and differential elastic cross section was presented in the article.…”