A study of charged kappa in $J/\psi \to K^{\pm} K_s \pi^{\mp} \pi^0$

TL;DR

This study analyzes $J/ar{J}$ decays to identify the charged kappa resonance and reports its properties, along with observing a new decay channel, using a large dataset from BESII.

Contribution

First observation of the charged kappa resonance and the decay $J/ar{J} o K^*(892)^+ K^*(892)^-$ in $J/ar{J}$ decays.

Findings

Charged kappa pole at approximately 849-i256 MeV/c^2.

First observation of $J/ar{J} o K^*(892)^+ K^*(892)^-$ decay.

Branching ratio of the new decay channel measured as about 1.00e-3.

Abstract

Based on $58 \times 10^6 $ $J/\psi$ events collected by BESII, the decay $J/\psi \to K^{\pm} K_s \pi^{\mp} \pi^0$ is studied. In the invariant mass spectrum recoiling against the charged $K^*(892)^{\pm}$, the charged $\kappa$ particle is found as a low mass enhancement. If a Breit-Wigner function of constant width is used to parameterize the kappa, its pole locates at $(849 \pm 77 ^{+18}_{-14}) -i (256 \pm 40 ^{+46}_{-22})$ MeV/$c^2$. Also in this channel, the decay $J/\psi \to K^*(892)^+ K^*(892)^-$ is observed for the first time. Its branching ratio is $(1.00 \pm 0.19 ^{+0.11}_{-0.32}) \times 10^{-3}$.