Search for formation of isospin-3/2 $\Xi$ states by neutrinos

Abstract

A narrow peak near 1870 MeV is observed in the combined invariant-mass spectrum of the systems $\Lambda K^0_S \pi^-$, $\Lambda K^0_S \pi^+$, $\Lambda K^- \pi^-$, and $\Lambda K^- \pi^+$ formed in $\nu_\mu$- and $\bar{\nu_\mu}$-induced charged-current collisions with free protons, deuterons, and Neon nuclei. Observed width of the resonance is consistent with being entirely due to apparatus smearing. A possible interpretation of the peak is formation and three-body $\Lambda K \pi$ decay of an exotic baryon with $I = 3/2$ and $S = -2$.