Weak decay of P shell lambda hypernuclei

Methods and results of an experiment to study the weak decay of Lambda hypernuclei are presented. The hypernuclei under study were 12C, 11B, plus a hypernuclear of unknown charge and mass designed /sup a/Z. The hypernuclear production data were obtained using the Hypernuclear Spectrometer and the Low Energy Separated Beam (LESB I), at the AGS of Brookhaven National Laboratory. The Kaon beam momentum was 805 MeV/c. Three hypernuclear states were observed, the 12C ground state, the P substitutional state, and the S substitutional state. The P substitutional state has been previously observed to decay to 11B plus a low energy proton. Hence, decay products observed in coincidence with this state are from the weak decay of 11B. The S substitutional state is shown to decay to a stable but unidentified hypernucleus. The protons from the nonmesonic decay branch, and the negative pion from the mesonic decay branch were detected in a 14 elements scintillator range spectrometer. The neutrons from the nonmesonic decay branches were detected in a 24 element neutron detector. The experimental results are compared with several calculations for hypernuclear nonmesonic decay in infinite nuclear matter and in finite nuclei. Several of these calculations agree favorably with the total nonmesonic rate, but none of the calculations are able to determine both the nonmesonic rate and the neutron stimulated fraction. 40 refs., 103 figs., 25 tabs