$\Xi$-nuclear constraints from $\Xi^-$ emulsion capture events

Abstract

All five KEK and J-PARC two-body $\Xi^-$+$^A$Z $\to$ $^{A'}_{\Lambda}$Z'+$^{A''}_{\Lambda}$Z'' capture events in light emulsion nuclei, including KISO and IBUKI in $^{14}$N, are consistent with Coulomb-assisted $1p_{\Xi^-}$ nuclear states. The underlying $\Xi$-nuclear potential is strongly attractive, with nuclear-matter depth $V_{\Xi}$ larger than 20 MeV. The recent $^{14}$N capture events KINKA and IRRAWADDY assigned by J-PARC E07 to $1s_{\Xi^-}$ nuclear states, and implying considerably shallower $V_{\Xi}$, have also another interpretation as $1p_{\Xi^0}$ nuclear states.