Speaker
Description
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. This peak could be a signal of the lightest kaonic nuclei, that is, the $\bar{K} N N (I=1/2)$ state, which has been intensively studied both experimentally and theoretically in the last decade. In this contribution we theoretically investigate what is the origin of the peak structure observed in the E15 experiment at J-PARC. Since the peak exists near the $K^- p p$ threshold, we expect two scenarios to produce the peak. One is that the $\Lambda(1405)$ is generated but it does not correlate with $p$, and the uncorrelated $\Lambda(1405)$-$p$ system subsequently decays into $\Lambda p$. The other is that the $\bar{K} N N$ quasi-bound state is indeed generated and decays into $\Lambda p$. We calculate the $\Lambda p$ invariant mass spectrum of the reaction with these two scenarios and compare it with the experimental one to interpret the experimental peak structure.
