Single and double coincidence nucleon spectra in the weak decay of Λ-hypernuclei

Single and double coincidence nucleon spectra in the weak decay of Λ-hypernuclei are studied within a nuclear matter formalism extended to finite nuclei via the local density approximation. With respect to previous calculations, the present work adopts a unified microscopic approach for both the one- and two-body induced mechanisms, including the channels Λnn→nnn and Λpp→npp in addition to the mode Λnp→nnp already considered in earlier phenomenological studies. The propagation of the final nucleons in the residual nucleus is simulated by an intranuclear cascade code. Through the comparison of our predictions with 12ΛC KEK nucleon coincidence data obtained with a nucleon kinetic energy threshold of 30 MeV and an opening angle region cosθNN≤-0.7 we determine Γn/Γp=0.66±0.24. We find that the value of Γn/Γp extracted from single nucleon distributions is strongly affected by final state interaction effects. Some discrepancies between measured and calculated proton spectra are also pointed out.