INVESTIGADORES
BARBERO Cesar Alberto
artículos
Título:
Intrinsic asymmetry parameter in nonmesonic hypernuclear decay: analytical proof of the independence on hypernucleus within an independent particle shell model
Autor/es:
C. BARBERO AND A. MARIANO
Revista:
BRAZILIAN JOURNAL OF PHYSICS
Editorial:
SOC BRASILEIRA FISICA
Referencias:
Año: 2009 vol. 39 p. 91 - 97
ISSN:
0103-9733
Resumen:
We derive general analytical expressions for the
evaluation of the intrinsic asymmetry parameter in nonmesonic hypernuclear weak
decay, within an independent particle shell model framework. Present formalism
is valid for even-even, even-odd and odd-odd core hypernucleus. A standard
strangeness-changing weak transition potential with exchange of the complete
meson octet ($pi,eta,K, ho,omega,K^*$) is assumed. Very simple analytical
formulas are obtained within the $s$-wave approximation when we restrict to the
$pi$ and $pi+K$ exchange models, providing an useful and manageable tool to
understand the origin of the discrepancies 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 exhibited. Present formalism could be used to understand why
new contributions to the exchange potential allow to obtain good agreement with
data, as indicated in very recent works. The necessity of a consistent
inclusion of: i) different modifications of the exchange potential (two-pion
exchange, $a_1$ meson, $Delta T=3/2$ terms coming from vector mesons, etc); ii)
final state interactions on primary nucleons inside the residual nucleus and
also correlations between the free emitted ones; and iii) configuration mixing
in the final system, is remarked.