Are orbiting resonances still possible in antiproton-nucleus scattering?

doi:10.1016/0370-2693(84)91069-4

Physics Letters B

Volume 139, Issue 4, 17 May 1984, Pages 231-234

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Abstract

New data from LEAR on the elastic scattering of antiprotons from ¹²C at 46.8 MeV are analyzed in light of previous theoretical predictions. It is found that the data support both strongly and weakly absorbing potential descriptions and hence do not rule out orbiting resonances. Further experiments are required to settle this question.

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Cited by (13)

Theoretical and numerical study of transport collision integrals: Application to O(3P)–O(3P) interaction
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In this paper we are introducing a new approach to calculate the classical transport collision integrals. The singularities (Glory, Rainbow and Orbiting) that occur when evaluating the scattering cross section have been taken into account. Clenshaw-Curtis quadrature has been adopted to evaluate numerically the three integrals (deflection angle, total cross section and the collision integral). Analytical formulates have been used in the area where singularities occur. The transport coefficients (viscosity, diffusion coefficient, thermal and electrical conductivities) strongly depend on the nature of the interaction between the particles that form the gas or the plasma and that is why it is necessary to determine the interaction potential accurately. To describe the interaction potential between two neutral particles we have opted for the Hulburt-Hirschfelder potential function. The results obtained are reported and compared to those in literature.
Low energy antiproton physics in the early LEAR era
1987, Progress in Particle and Nuclear Physics
This review concentrates on developments, both experimental and theoretical, that have occurred in the field of low energy antinucleon physics since 1983—the year in which the Low Energy Antiproton Ring opened in CERN. On the theoretical side the emphasis is on the progress made in describing $N N$ annihilation and meson branching ratios in terms of quark-antiquark rearrangement and annihilation. The related processes involving the $p - Nucleus$ system are also discussed.
Microscopic calculation of antiproton-nucleus elastic scattering
1986, Nuclear Physics, Section A
The antiproton-nucleon T-matrix of the Dover-Richard interaction is fitted by a linear combination of simple functions. The one-pion exchange potential is included explicitly, and the remainder is approximated by either Gauss or Yukawa functions. Including a linear energy dependence improves the fit significantly. The optical potential is then obtained by folding with the nuclear density, taking into account the size of the antiproton. When an energy or relative momentum-squared dependence of the central part of the T-matrix is included, the corresponding gradient operators lead to an optical potential containing unusual terms. This corresponds to a generalization of Skyrme-like forces to finite range and to the inclusion of an imaginary effective mass. For scattering the latter term is equivalent to a definite energy-dependent optical potential. Elastic scattering cross sections for 300 and 600 MeV/c antiprotons on ¹²C, ⁴⁰Ca and ²⁰⁸Pb are computed using the KMT procedure for the optical potentials resulting from the various T-matrix approximations. Comparisons with available experimental values give $solχ^{2} N$ values typically around 4. The different choices of functions give rather similar results.
Optical-model analysis of antiproton-nucleus elastic scattering at 50 and 180 MeV
1986, Nuclear Physics, Section A
Accurate antiproton-nucleus elastic scattering angular distributions measured at two incident energies,∼50 and ∼180 MeV, on ¹²C, ⁴⁰Ca, ²⁰⁸Pb and at 178.4 MeV on ^16,18O have been analysed in the framework of the optical model. Extensive searches on the relative sensitivities to the different potential parameters have been done. Optical potentials with charge-distribution geometries failed in reproducing the experimental data; the finite range of the interaction has to be taken into account. The corresponding optical potentials have shallow real parts 5 MeV ⩽ V₀ ⩽ 105 MeV, their imaginary depths are at least twice larger than their real depths. These features rule out some models but are consistent with an analysis of recent $p -atom$ data. The sensitivity of the optical-model analysis of elastic scattering data to the details of the radial potential has been investigated. Target mass and energy evolution of the strong-absorption radius and reaction cross section confirm that the antiproton penetrates more inside the target nucleus when the incident energy increases. Some features of the phenomenological potentials are compared with the predictions of microscopic potentials.
Analysis of antiproton-nucleus scattering with the medium-corrected optical potential
1985, Nuclear Physics, Section A
The antiproton-nucleon effective interaction evaluated in nuclear matter is used to construct the $p - nucleus$ optical potential. It is found that the resulting optical potential is largely modified by the nuclear medium to be attractive in the inner region of the nucleus, strongly absorptive and moderately energy-dependent at the energies concerned here (E ≲ 180 MeV). The differential cross sections for elastic and inelastic $p - nucleus$ (C, Al, Ca, Cu and Pb; only C for the inelastic case) scattering are calculated. The results obtained with the medium-corrected optical potential are in better agreement with experimental data than those with the free t-matrix. Within the measured range of the scattering angle, however, the effect of the medium correction on these quantities does not seem to be quite so prominent in spite of the drastic change of the optical potential. The spin-orbit component of the optical potential is also evaluated and found to be largely suppressed in the nuclear medium. The calculated polarization is very different from that obtained with the free t-matrix. Therefore the first measurement of the polarization should be a crucial test of the applicability of our approach.
Combined analysis of antiprotonic atoms and antiproton elastic scattering data
1985, Nuclear Physics, Section A
Experimental results for a range of antiprotonic atoms and for the elastic scattering of 47 MeV antiprotons by C are analysed using the optical model. Unambiguous potentials are found for antiprotonic atoms; the results are also fitted using a finite-range interaction. Model-independent potentials are obtained from the scattering data at 47 MeV and compared with potentials obtained from a folding model. The consistency between the antiprotonic atom potentials and the scattering potentials is discussed together with the question of how deep the antiprotons probe into the nucleus.

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^☆: Work supported under contract DE-AC02-76CH00016 with the U.S. Department of Energy.

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Are orbiting resonances still possible in antiproton-nucleus scattering?☆

Abstract

Phys. Rev. Lett.

At. Data Nucl. Data Tables

Comput. Phys. Commun.

Los Alamos report LA-5110