Study of $\chi_{cJ}$ decaying into $\phi$ $K^*(892)$ $\bar{K}$

TL;DR

This study investigates the decay of $ ext{chi}_{cJ}$ into $ ext{phi}$ and $K^*$ mesons using BESIII data, revealing a new structure near the $K^*(892)ar{K}$ threshold consistent with the $h_1(1380)$ state.

Contribution

First measurement of $ ext{chi}_{cJ}$ decays into $ ext{phi} K^*(892)ar{K}$ with observation of a new structure near threshold, supporting the identification with $h_1(1380)$.

Findings

Branching fractions consistent with isospin symmetry.

Observation of a structure near the $K^*(892)ar{K}$ threshold.

Mass and width measurements support the $h_1(1380)$ assignment.

Abstract

Using a data sample of 106 million $\psi(3686)$ events collected with the BESIII detector operated at the BEPCII storage ring, we study for the first time the decay $\chi_{cJ}\to\phi K^{0}_S K^{\pm}\pi^{\mp}$ and $\chi_{cJ}\to\phi K^{+} K^{-}\pi^{0}$ in the E1 radiative transition $\psi(3686)\to\gamma\chi_{cJ}$. The decays are dominated by the three-body decay $\chi_{cJ}\to \phi K^*(892)\bar{K}$. We measure branching fractions for this reaction via the neutral and charged $K^*(892)$ and find them consistent with each other within the expectation of isospin symmetry. In the $K\bar{K}\pi$ invariant mass distribution a structure near the $K^*(892)\bar{K}$ mass threshold is observed, and the corresponding mass and width are measured to be $1412\pm4(\mathrm{stat.})\pm8(\mathrm{sys.}) \mathrm{MeV}/c^2$ and $\Gamma$ = $84\pm12(\mathrm{stat.})\pm40(\mathrm{sys.}) \mathrm{MeV}$, respectively. The observed state favors an assignment to the $h_1(1380)$, considering its possible $J^{PC}$ and comparing its mass, width and decay mode to those reported in the Particle Data Group.