Observation of $\Xi(1620)^0$ and evidence for $\Xi(1690)^0$ in $\Xi_c^+ \rightarrow \Xi^-\pi^+\pi^+$ decays

TL;DR

This paper reports the first observation of the $ ext{Xi}(1620)^0$ baryon and evidence for $ ext{Xi}(1690)^0$ in specific decay channels, providing new insights into hyperon resonance structures with strangeness $S=-2$.

Contribution

First observation of $ ext{Xi}(1620)^0$ and evidence for $ ext{Xi}(1690)^0$ in $ ext{Xi}_c^+$ decays, expanding knowledge of hyperon resonances with strangeness $S=-2$.

Findings

Mass of $ ext{Xi}(1620)^0$ measured at 1610.4 MeV/c^2

Width of $ ext{Xi}(1620)^0$ measured at 59.9 MeV

4.0$\sigma$ evidence for $ ext{Xi}(1690)^0$

Abstract

We report the first observation of the doubly-strange baryon $\Xi(1620)^0$ in its decay to $\Xi^-\pi^+$ via $\Xi_c^+ \rightarrow \Xi^- \pi^+ \pi^+$ decays based on a $980\,{\rm fb}^{-1}$ data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The mass and width are measured to be 1610.4 $\pm$ 6.0 (stat) $^{+5.9}_{-3.5}$ (syst)~MeV$/c^2$ and 59.9 $\pm$ 4.8 (stat) $^{+2.8}_{-3.0}$ (syst)~MeV, respectively. We obtain 4.0$\sigma$ evidence of the $\Xi(1690)^0$ with the same data sample. These results shed light on the structure of hyperon resonances with strangeness $S=-2$.