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Two-Pion-Exchange Contribution to the Λ -Nucleon Scattering Matrix

1963; American Institute of Physics; Volume: 131; Issue: 1 Linguagem: Inglês

10.1103/physrev.131.390

1536-6065

R. Schrils, B. W. Downs,

Nuclear physics research studies

The two-pion-exchange (TPE) contribution to the $\ensuremath{\Lambda}$-nucleon scattering matrix has been calculated with the Dyson $S$-matrix formalism under the assumption of even $\ensuremath{\Lambda}\ensuremath{-}\ensuremath{\Sigma}$ parity and a universal pion-baryon interaction. This calculation leads to a TPE contribution to the zero-energy $\ensuremath{\Lambda}$-nucleon scattering length which is spin-independent. For scattering at finite energies, the scattering matrix is spin-dependent and contains an anti-symmetric spin-orbit term, which does not appear in the charge-symmetric nucleon-nucleon scattering matrix. The results suggest the use of a semiphenomenological $\ensuremath{\Lambda}$-nucleon potential which, for large separations, is predominantly spin-independent.