IFLP   13074
INSTITUTO DE FISICA LA PLATA
Unidad Ejecutora - UE
artículos
Título:
Nonmesonic Weak Decay of $\Lambda$-Hypernuclei within Independent-Particle Shell-Model
Autor/es:
FRANJO KRMPOTIC; ALFREDO P. GALEÃO; MAHIR S. HUSSEIN
Revista:
AIP CONFERENCE PROCEEDINGS
Editorial:
American Institute of Physics
Referencias:
Lugar: New York; Año: 2010 vol. 1245 p. 51 - 76
ISSN:
0094-243X
Resumen:
After a short introduction to  the nonmesonic weak decay (NMWD)$\Lambda N\go nN$ of $\Lambda$-hypernuclei we discuss thelong-standing puzzle on the ratio $\Gamma_n/\Gamma_p$, and somerecent  experimental evidences that signalized towards  its finalsolution. Two versions of the  Independent-Particle-Shell-Model(IPSM) are employed to account for the nuclear structure of  thefinal residual nuclei. They are: (a) IPSM-a, where  nocorrelation, except for the Pauli principle, is  taken intoaccount, and (b) IPSM-b, where the highly excited  hole states areconsidered to be quasi-stationary and are described byBreit-Wigner distributions, whose widths are estimated from theexperimental data. We evaluate  the  coincidence spectra in$^{4}_\Lambda$He, $^{5}_\Lambda$He, $^{12}_\Lambda$C,$^{16}_\Lambda$O, and $^{28}_\Lambda$Si, as a function of the  sumof kinetic energies $E_{nN}=E_n+E_N$ for $N=n,p$.  The recentBrookhaven National Laboratory experiment E788 on $^4_\Lambda$He,is interpreted within the IPSM . We found that  the shapes of allthe spectra are basically tailored by the kinematics of thecorresponding phase space, depending very weakly on the dynamics,which is gauged here by the one-meson-exchange-potential. In spiteof the straightforwardness of the approach a good agreement withdata is achieved. This might be an indication that thefinal-state-interactions and the two-nucleon induced processes arenot very important  in the decay of this hypernucleus. We havealso found that the $\pi+K$ exchange potential with softvertex-form-factor cutoffs $(\Lambda_\pi\approx 0.7$ GeV,$\Lambda_K\approx 0.9$ GeV), is able to account simultaneously forthe available experimental data related to $\Gamma_p$ and$\Gamma_n$ for  $^4_\Lambda$H, $^4_\Lambda$He, and $^5_\Lambda$He.