Polarization and weak decay of Λ hypernuclei

In the recent experiment the authors have produced polarized hypernuclei and studied weak and strong Λ nucleon interaction in a nucleus. The 12C(π+, K+) reaction was used to produce polarized Λ hypernuclei. Asymmetries of weak decay particles were measured. Polarization of Λ produced by the quasifree process was derived. The polarization is shown to be consistent with that of the elementary n(π+, K+)Λ reaction which demonstrates that the spin characteristics of the elementary reaction is not modified by the nuclear medium. The authors have observed asymmetry of protons from the nonmesonic decay. The large asymmetry parameter (∼ -1) of the non-mesonic decay demonstrates the existence of the interference between parity changing and parity conserving amplitudes in the strangeness changing baryon baryon interaction for the first time. The large asymmetry parameter, whose accuracy will be improved by the coming experiment, will elucidate the non-mesonic decay mechanism and open a new field of hypernuclear physics