Proton asymmetry in non-mesonic weak decay of light hypernuclei

We have obtained the decay asymmetry parameters in non-mesonic weak decay of polarized Λ-hypernuclei by measuring the proton asymmetry. The polarized Λ-hypernuclei, 5ΛHe, 12ΛC, and 11ΛB, were produced in high statistics via the (π+,K+) reaction at 1.05 GeV/c in the forward angles. Preliminary analysis shows that the decay asymmetry parameters are very small for these s-shell and p-shell hypernuclei.