A couple of years ago, heavy-ion based experiments (HypHI, STAR and ALICE) announced surprisingly short lifetime for ³_ΛH mesonic weak decay (MWD), which is difficult to interpret given the fact that ³_ΛH is a very loosely bound system. It will be very interesting to study this issue with a different experimental approach.
We propose a direct measurement for ³_ΛH hypernucleus MWD lifetime with ~10% resolution as J-PARC E73 experiment; ⁴_ΛH hypernucleus lifetime will also be measured as a feasibility test for our experimental approach. In this talk, I will introduce our experimental method and the current status of E73 experiment.