$^{31}$Ar examined: new limit on the $\beta$-delayed three-proton branch

We have remeasured the decay of $^{31}$Ar with a setup sensitive to multiparticle decay branches and obtained a new limit of 1.1 × $10^{-3}$(99%C.L.) on the $\beta$-delayed three-proton branch between the isobaric analog state in $^{31}$Cl and the ground state of $^{28}$Si. This a factor of 17 below the previously reported first observation of $\beta$-delayed three-proton emission in $^{31}$Ar. The limit on a possible $\beta$-3p branch to the first excited state in $^{28}$Si is 2.9 × 10$^{-4}$.