INVESTIGADORES
BARBERO Cesar Alberto
artículos
Título:
Shell model formalism for all hypernuclei types: a guide to solving the nonmesonic weak decay puzzle
Autor/es:
C. BARBERO, A. MARIANO Y A. SAMANA
Revista:
Physical Review C
Editorial:
American Physical Society
Referencias:
Año: 2008 vol. 78 p. 443241 - 443248
ISSN:
0556-2813
Resumen:
We extend
to odd-odd core hypernuclei our independent particle shell model (IPSM)
formalism developed previously for the evaluation of the $Gamma_{NM}$,
$Gamma_{n/p}$ and a_Lambda$ hypernuclear weak decay observables. The present
procedure reproduces the even-odd and even-even core results as particular
cases. Adopting the standard strangeness-changing weak $Lambda N o NN$
transition potential with exchange of the complete pseudoscalar and
vector meson octets ($pi,eta,K, ho,omega,K^*$) we get simple analytical
expressions for all observables. 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 obtained and compared
with available experimental data, putting special attention on the asymmetry
parameter. We remark that, in the present form, the IPSM gives roughly the same
value of $a_Lambda$ for all hypernucleus in contradiction with experiments. We
stress the necessity of: i) introduce configuration mixing to go beyond the
IPSM and take into account in a more realistic way nuclear structure effects,
and/or include more relevant degrees of freedom, still within the IPSM
framework, like: ii) modifications of the exchange potential (two-pion, $a_1$
meson, $Delta T=3/2$ terms of vector mesons, etc.), iii) final state
interactions accounting for the distortion of the plane waves of emitted
nucleons, and iv) two-nucleon induced decay, as possible ways to solve the
puzzle.