One-proton emission from the $^6_{\Lambda}$Li hypernucleus

Abstract

One-proton (1p) radioactive emission under the influence of the $\Lambda^0$-hyperon inclusion is discussed. I investigate the hyper-1p emitter, $^6_{\Lambda}$Li, with a time-dependent three-body model. Two-body interactions for $\alpha$-proton and $\alpha$-$\Lambda^0$ subsystems are determined consistently to their resonant and bound energies, respectively. For a proton-$\Lambda^0$ subsystem, a contact interaction, which can be linked to the vacuum-scattering length of the proton-$\Lambda^0$ scattering, is employed. A noticeable sensitivity of the 1p-emission observables to the scattering length of the proton-$\Lambda^0$ interaction is shown. The $\Lambda^0$-hyperon inclusion leads to a remarkable fall of the 1p-resonance energy and width from the hyperon-less $\alpha$-proton resonance. For some empirical values of the proton-$\Lambda^0$ scattering length, the 1p-resonance width is suggested to be of the order of $0.1-0.01$ MeV. Thus, the 1p emission from $^6_{\Lambda}$Li may occur in the timescale of $10^{-20}-10^{-21}$ seconds, which is sufficiently shorter than the self-decay lifetime of $\Lambda^0$, $10^{-10}$ seconds. By taking the spin-dependence of the proton-$\Lambda^0$ interaction into account, a remarkable split of the $J^{\pi}=1^-$ and $2^-$ 1p-resonance states is predicted. It is also suggested that, if the spin-singlet proton-$\Lambda^0$ interaction is sufficiently attractive, the 1p emission from the $1^-$ ground state is forbidden. From these results, I conclude that the 1p emission can be a suitable phenomenon to investigate the basic properties of the hypernuclear interaction, for which a direct measurement is still difficult.