Proton energy spectra in the nonmesonic weak decay of 12lambdaC and 28lambdaSi hypernuclei

Phys Rev Lett. 2002 Jan 28;88(4):042503. doi: 10.1103/PhysRevLett.88.042503. Epub 2002 Jan 14.

Abstract

Numbers of protons per Gamma hypernuclear weak decay were measured as a function of proton energy above 40 MeV, explicitly identifying production of Gamma hypernuclei by the (pi+,K+) reaction. The ratios between the neutron-stimulated to proton-stimulated nonmesonic decay widths, Gamma((Lambda)n-->nn)/Gamma((Lambda)p-->np) ( = Gamma(n)/Gamma(p)) were extracted by fitting the proton energy spectra. The present result claims that the proton yields are suppressed and the Gamma(n)/Gamma(p) ratios are close to 1 both for 12LambdaC and 28LambdaSi in contradiction to theoretical expectations based on meson exchange models.