Weak decay of polarized Λ hypernuclei

The non mesonic decay of Λ hypernuclei is investigated in a relativistic nuclear model which includes, apart from the conventional pion mechanism, the exchange of the heavier mesons. The non mesonic decay rate and the proton asymmetry are in agreement with present experimental data. It is found that these observables are dominated by one pion exchange, since short range ΛN correlations supress the contribution from heavier mesons. The neutron to proton induced ratio, more sensitive to the isospin structure at the vertices, is increased by about 30%. However, the theoretical result is still far off the present experimental value. ((orig.))