Pionic-decay spectra of few-body Λ-hypernuclei

Pionic-decay spectra are discussed in A=4 and 5 Λ-hypernuclei by using wave-functions obtained by the resonating group method. For Λ5He, the π--spectrum shows a sharp peak at 171 MeV with 1.5 MeV FWHM in the total pion energy. For Λ4H and Λ4He, the spectra have broad peaks around 170 MeV with 6-7 MeV FWHM. This difference is caused by resonance structures of the final-state nuclei under the spin-non-flip dominance in the pionic decay. Partial decay widths are calculated to check the normalization of the spectra, and are in systematically good agreement with all available experimental data. The pionic weak-decay of ΛΛ5H is also investigated to show the feasibility of the nuclear identification by using monoenergetic decay pions. (author)