Regular Article - Theoretical Physics
The σK coupling in the chiral unitary approach and the isoscalar ¯N , ¯A interaction
Departamento de Fısica Teórica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigación de Paterna, Aptdo. 22085, 46071, Valencia, Spain
Accepted: 8 April 2008
Published online: 2 May 2008
We evaluate the “σ " exchange contribution to the ¯N → ¯N scattering within a chiral unitary approach. We show that the chiral transition potentials for ππ → K¯ in the t -channel lead to a “σ " contribution that vanishes in the ¯ forward direction and, hence, would produce a null “σ " exchange contribution to the K- optical potential in nuclear matter in a simple impulse approximation. This is a consequence of the fact that the leading-order chiral Lagrangian gives an I = 0 ππ → K¯ amplitude proportional to the squared momentum transfer, q2. This finding poses questions on the meaning or the origin of “σ " exchange potentials used in relativistic mean-field approaches to the K- nuclear self-energy. This elementary “σ ” exchange potential in ¯N → ¯N is compared to the Weinberg-Tomozawa term and is found to be smaller than the present theoretical uncertainties but will be relevant in the future when aiming at fitting increasingly more accurate data.
PACS: 21.65.Jk Mesons in nuclear matter – / 25.80.Nv Kaon-induced reactions – / 21.65.-f Nuclear matter –
© Società Italiana di Fisica and Springer-Verlag, 2008