Proton asymmetry in non-mesonic weak decay of light hypernuclei

We have obtained the decay asymmetry parameters in non-mesonic weak decay of polarized Lambda-hypernuclei by measuring the proton asymmetry. The polarized Lambda-hypernuclei, 5_Lambda-He, 12_Lambda-C, and 11_Lambda-B, were produced in high statistics via the (pi^+,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.