Three-Body Nonmesonic Weak Decay of the {sub {Lambda}{sup 12}}C Hypernucleus

We have measured the branching ratio of the three-body process in the nonmesonic weak decay of {sub {Lambda}{sup 12}}C to be 0.29+-0.13. This result was obtained by reproducing the nucleon and the nucleon pair yields introducing a measured final state interaction. At the same time, we have determined the absolute decay widths, GAMMA{sub n} and GAMMA{sub p}, along with GAMMA{sub 2N}, whose relative ratio has been a long-standing puzzle. Including the three-body process, we have successfully reproduced the nucleon energy distribution, the coincidence two-nucleon angular correlation, and the momentum sum distribution simultaneously.