Spin observables in the pn→pΛ reaction

The T matrix of the pn→pΛ reaction, which is a strangeness changing weak process, is derived. The explicit formulas of the spin observables are given for s-wave pΛ final states which kinematically corresponds to inverse reaction of the weak nonmesonic decay of Λ hypernuclei. One can study interferences between amplitudes of the parity-conserving and -violating, spin-singlet and -triplet, and isospin-singlet and -triplet. Most of them are not available in the study of the nonmesonic decay and will be measured in the coming experiment. They clarify the structure of the reaction and constrain strongly theoretical models for the weak hyperon nucleon interaction.