What makes the peak structure of the $\Lambda p$ invariant-mass spectrum in the $K^{-} {}^{3} {\rm He} \to \Lambda p n$ reaction?

Abstract

Recently a peak structure was observed near the $K^{-} p p$ threshold in the in-flight ${}^{3} {\rm He} (K^{-} , \, \Lambda p) n$ reaction of the E15 experiment at J-PARC, which could be a signal of a $\bar{K} N N$ bound state. In order to investigate what is the origin of this peak, we calculate the cross section of this reaction, in particular based on the scenario that the $\bar{K} N N$ bound state is indeed generated and decays into $\Lambda p$. We find that the numerical result of the $\Lambda p$ invariant-mass spectrum in the $\bar{K} N N$ bound scenario is consistent with the J-PARC E15 data.