Effects of Δ-isobar degrees of freedom on low-energy electroweak transitions in few-body nuclei

Phys. Rev. C 45, 2628 – Published 1 June 1992
R. Schiavilla, R. B. Wiringa, V. R. Pandharipande, and J. Carlson

Abstract

Variational wave functions with Δ-isobar components are used to study trinucleon magnetic moments, the Gamow-Teller matrix element of tritium β decay, thermal neutron radiative capture on He3, and low-energy proton weak capture on He3. The Δ-isobar components are generated by transition correlation operators acting on realistic nuclear wave functions. These correlations are obtained from a fit to exact two-body ground-state and low-energy scattering solutions for the Argonne v28 and v28Q interaction models, which include Δ-isobar degrees of freedom. Contributions of Δ isobars to electroweak current operators appear at the one-body level in this formalism. Their effect on low-energy electroweak transitions is significantly smaller than that obtained in perturbation theory analyses, where Δ-isobar effects are commonly subsumed into effective two-body current operators. The resulting theoretical cross section for thermal neutron radiative capture on He3 is ≊86 μb, compared to an experimental value of 55±3 μb; the astrophysical S factor for proton weak capture on He3 is predicted to be in the range (1.4–3.2)×10-23 MeV b.

DOI: http://dx.doi.org/10.1103/PhysRevC.45.2628

  • Received 25 November 1991
  • Published in the issue dated June 1992

© 1992 The American Physical Society

Authors & Affiliations

R. Schiavilla and R. B. Wiringa

  • Physics Division, Argonne National Laboratory, Argonne, Illinois 60439

V. R. Pandharipande

  • Department of Physics, University of Illinois, Urbana, Illinois 61801

J. Carlson

  • Theory Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545

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