Mass--dependence of the Lambda hypernuclear decay widths

Abstract

Two different approaches have been employed for the evaluation of the decay widths of Lambda-hypernuclei (ranging from $^5_Λ$He to $^{208}_Λ$Pb) with the polarization propagator method. In ref.[1], the two-nucleon stimulated non-mesonic decay, $ΛNN\to NNN$, has been parameterized phenomenologically by means of data on the pion-nucleus optical potential. The other approach [2] consisted in a fully microscopic description of the non-mesonic decays through the first order approximation of the so-called bosonic-loop-expansion. Both calculations reproduce, with approximately the same accuracy, the experimental decay rates for the whole range of mass numbers considered.