decay rates of p-shell hypernuclei revisited

✍ Scribed by Avraham Gal

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 172 KB
• Volume: 828
• Category: Article
• ISSN: 0375-9474
• DOI: 10.1016/j.nuclphysa.2009.06.026

✦ Synopsis

Explicit expressions for the parity-violating s-wave and the parity-conserving p-wave contributions to π -weak decay rates of Λ hypernuclei in the 1p shell are given in the weak-coupling limit, to update previous shell-model calculations and to compare with recent π -spectra and total decay rates measured by the FINUDA Collaboration for 7 Λ Li, 9 Λ Be, 11 Λ B and 15 Λ N. A useful sum rule for the summed strength of Λ 1s → p 1p hypernuclear π -weak decays is derived. Fair agreement between experiment and calculations is reached, using the primary s-wave amplitude and Cohen-Kurath nuclear wavefunctions. The role of the p-wave amplitude is studied in detail for 15 Λ N and found to be secondary. Previous assignments of ground-state spin-parity values J π ( 7 Λ Li g.s. ) = 1 2 + and J π ( 11 Λ B g.s. ) = 5 2 + are confirmed, and a new assignment J π ( 15 Λ N g.s. ) = 3 2 + is made, based on the substantial suppression calculated here for the 15 Λ N( 1 2 + ) → π -15 O g.s. weak decay rate.