Search for the light hadron decay $\chi_{c1}(3872) \to \pi^{+}\pi^{-}\eta$

TL;DR

This study searches for the light hadron decay mode of the $ ext{chi}_{c1}(3872)$ particle using BESIII data, setting upper limits on its decay probability due to no significant signal detection, which informs its internal structure understanding.

Contribution

First experimental search for $ ext{chi}_{c1}(3872) o ext{pi}^+ ext{pi}^- ext{eta}$ decay mode, establishing upper limits on its production and decay ratios.

Findings

No significant signal observed for the decay mode.

Upper limits set on the production cross section times branching ratio.

Branching fraction ratio upper limit $ ext{<}0.12$ at 90\% confidence level.

Abstract

With a data sample corresponding to an integrated luminosity of 11.5~fb$^{-1}$ collected with the BESIII detector operating at the BEPCII storage ring, for the first time the light hadron decay $\chi_{c1}(3872) \rightarrow \pi^{+}\pi^{-}\eta$ is searched for. While no significant signal is observed, the upper limits at the 90\% confidence level for $\sigma[e^{+}e^{-} \rightarrow \gamma \chi_{c1}(3872)] \mathcal{B}[\chi_{c1}(3872) \rightarrow \pi^{+}\pi^{-}\eta]$ at center-of-mass energies from 4.13 to 4.34 GeV are determined. By normalizing to the $\chi_{c1}(3872)\to\pi^+\pi^- J/\psi$ decay channel, a 90\% confidence level upper limit for the branching fraction ratio $\mathcal{R}=\mathcal{B}[\chi_{c1}(3872) \rightarrow\pi^{+}\pi^{-}\eta]/\mathcal{B}[\chi_{c1}(3872) \rightarrow \pi^{+}\pi^{-} J/\psi] < 0.12$ is given. These measurements provide important inputs for understanding the internal structure of the $\chi_{c1}(3872)$ resonance.