Study of some two-body non-mesonic decays of $^4_\Lambda$He and $^5_\Lambda$He

TL;DR

This study reports the first measurements of two-body non-mesonic decay channels of $^4_ ext{Lambda}$He and $^5_ ext{Lambda}$He hypernuclei, providing new decay yields and branching ratios that enhance understanding of hypernuclear decay processes.

Contribution

The paper presents the first experimental assessment of decay yields and branching ratios for specific two-body non-mesonic decay channels of hyperhelium isotopes.

Findings

Decay yield for $^4_ ext{Lambda}$He to $d+d$ is $(1.37 extpm 0.37) imes 10^{-5}/K^-_{stop}$.

Decay yield for $^4_ ext{Lambda}$He to $p+t$ is $(8.3 extpm 1.0) imes 10^{-5}/K^-_{stop}$.

Branching ratio for $^5_ ext{Lambda}$He to $d+t$ is measured as $(3.0 extpm 2.3) imes 10^{-3}$.

Abstract

The Non-Mesonic (NM) decay of $^4_\Lambda{\mathrm{He}}$ and $^5_\Lambda{\mathrm{He}}$ in two-body channels has been studied by the FINUDA Collaboration. Two-body NM decays of hypernuclei are rare and the existing observations and theoretical calculations are scarce. The $^4_\Lambda{\mathrm{He}}\rightarrow d+d,\; p+t$ decay channels simultaneously observed by FINUDA on several nuclei are compared: the $pt$ channel is the dominant one. The decay yields for the two decay channels are assessed for the first time: they are $(1.37\pm 0.37)\times 10^{-5}/K^-_{stop}$ and $(8.3\pm 1.0)\times 10^{-5}/K^-_{stop}$, respectively. Due to the capability of FINUDA of identifying $^5_\Lambda{\mathrm{He}}$ hypernuclei, a few $^5_\Lambda{\mathrm{He}}\rightarrow d+t$ decay events have also been observed. The branching ratio for this decay channel has been measured for the first time: $(3.0\pm 2.3)\times 10^{-3}$.