Kinetic energy sum spectra in nonmesonic weak decay of hypernuclei

Abstract

We evaluate the coincidence spectra in the nonmesonic weak decay (NMWD) $ΛN\go nN$ of $\Lambda$ hypernuclei ${}_{\Lambda }^4$He, ${}_{\Lambda }^5$He, ${}_{\Lambda }^{12}$C, ${}_{\Lambda }^{16}$O, and ${}_{\Lambda }^{28}$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 parameterization. Two versions of the Independent-Particle Shell Model (IPSM) are employed to account for the nuclear structure of the final residual nuclei. They are: (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 quasi-stationary 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 $<E_{nN}<170$ MeV, one for each occupied shell-model state. The IPSM-a could be a pretty fair approximation for the light ${}_{\Lambda }^4$He and ${}_{\Lambda }^5$He hypernuclei. For the remaining, heavier, hypernuclei it is very important, however, to take into account 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.

arXiv commentv1: 20 pages, 3 figures, 1 table, submitted for publication; v2: minor corrections, improved figures, published version

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Cited by in corpus (9)

• Nonmesonic weak decay spectra of ${}_{\Lambda }^4$He
• Relationships between nonmesonic-weak-decays in different hypernuclei
• Weak nonmesonic decay spectra of hypernuclei
• Nonmesonic Hyperon Weak Decay Spectra in ${}_{\Lambda }^{12}$C}
• Nonmesonic weak decay spectra of light hypernuclei
• Nonmesonic weak decay of charmed hypernuclei
• Relativistic model for the nonmesonic weak decay of single-lambda hypernuclei
• Final state interaction in the pn and nn decay channels of ${}_{\Lambda }^4$He
• Delayed clusters accompanying nonmesonic weak decay of the $\Lambda$-hypernuclei: a clue to nonleptonic processes