Λ-N Weak-interaction, unitary symmetry and nucleon-nucleon-scattering phase shifts

Abstract

The weak interaction process ΛN → NN is studied under the assumption that the weak Hamiltonian transforms like scalar (for the parity-conserving part) and pseudoscalar (for the partity-violating part) densities which behave like the sixth (λ ₆) and seventh (λ ₇) components of an octet, respectively, under the SU(3) transformations. The six possible transition amplitudes can thus be expressed as products of a weak transition and a strong scattering amplitude. The scattering amplitude is expressed in terms of five invariant amplitudes which are related to the N-N scattering phase shifts. The ratio D^C/F^C for parity conserving weak transition is required to be equal to -3 to suppress the parity-conserving amplitudes. All the other parameters of the weak interaction are known from the weak pionic decay of baryons. The resulting rates for the transitions agree very well with regard to both relative and absolute magnitudes with the rates determined from the study of hypernuclear decays.