Intrinsic asymmetry parameter in nonmesonic hypernuclear decay: analytical proof of the independence on hypernucleus within an independent shell model

C. BARBERO, A. MARIANO

BRAZILIAN JOURNAL OF PHYSICS

Brazilian Physical Society

Lugar: San Pablo, Brasil; Año: 2009 vol. 31 p. 91 - 97

0103-9733

We derive a general expression for the evaluation of the intrinsicasymmetry parameter in nonmesonic hypernuclear weak decay, withinan independent particle shell model framework. Present formalismis valid for even-even, even-odd and odd-odd core hypernucleus. Astandard strangeness-changing weak transition potential withexchange of the complete meson octet($pi,eta,K, ho,omega,K^*$) is assumed.  Very simple analyticalformulas are obtained within the $s$-wave approximation, when werestrict to the $pi$ and $pi+K$ exchange models providing anuseful and manageable tool to understand the origin of thediscrepancies between theoretical and experimental results.Numerical values for $^{4}_Lambda He$, $^{5}_Lambda He$,$^{11}_Lambda B$, $^{12}_Lambda C$, $^{16}_Lambda O$,$^{17}_Lambda O$ and $^{28}_Lambda Si$ hypernuclei are exhibit.Our  results indicate the relevance of including  effects ofconfiguration mixing in the final system, avoiding  the shell factorizationeffect leading to constancy of asymmetry for the differenthypernuclei. The necessity of the two nucleon induced decay modeas consequence of the final state interactions with the ejected particles, in theframework of finite nucleus, is remarked.