INVESTIGADORES
BARBERO Cesar Alberto
artículos
Título:
Kinetic energy sum spectra in nonmesonic weak decay of hypernuclei
Autor/es:
C. BARBERO, A.P. GALEAO, M.S. HUSSEIN Y F. KRMPOTIC
Revista:
Physical Review C
Editorial:
American Physical Society
Referencias:
Año: 2008 vol. 78 p. 443121 - 4431213
ISSN:
0556-2813
Resumen:
We evaluate the coincidence spectra in the nonmesonic
weak decay (NMWD) Lambda N -> nN of Lambda hypernuclei 4^Lambda_He, 5^Lambda_He, 12^Lambda_C,
16^Lambda_O and 28^Lambda_Si, as a function of the sum of kinetic energies
E_nN = E_n + E_N
for N = n, p. The
strangeness-changing transition potential is described by the
one-meson-exchange model, with commonly used parametrization. Two versions of
the independent-particle shell model (IPSM) are employed to account for the
nuclear structure of the final residual nuclei. They are as follows: (a)
IPSM-a, where no correlation, except for the Pauli principle, is taken into
account and (b) IPSM-b, where the highly excited hole states are considered to
be quasistationary and are described by Breit-Wigner distributions, whose
widths are estimated from the experimental data. All np and nn spectra exhibit a
series of peaks in the energy interval 110 MeV <
EnN <170 MeV, one for each occupied shell-model state.
Within the IPSM-a, and because of the recoil effect, each peak covers an energy
interval proportional to A−1 , going from = 4 MeV for 28^Lambda_Si to =40 MeV for 4^Lambda_He. Such a description could be
pretty fair for the light 4^Lambda_He and 5^Lambda_He hypernuclei. For the remaining,
heavier, hypernuclei it is very important, however, to consider as well the
spreading in strength of the deep-hole states and bring into play the IPSM-b
approach. Notwithstanding the nuclear model that is employed the results depend
only very weakly on the details of the dynamics involved in the decay process
proper. We propose that the IPSM is the appropriate lowest-order approximation
for the theoretical calculations of the of kinetic energy sum spectra in the
NMWD. It is in comparison to this picture that one should appraise the effects
of the final-state interactions and of the two-nucleon-induced decay mode.