Search for $\chi_{c1}\to \pi^{+}\pi^{-}\eta_c$ via $\psi(3686)\to\gamma\chi_{c1}$

Abstract

Utilizing $(2712.4 \pm 14.3) \times 10^6$ $\psi(3686)$ events collected with the BESIII detector at the BEPCII collider, we search for the hadronic transition process $\chi_{c1} \to \pi^+\pi^-\eta_c$ following the decay $\psi(3686)\to \gamma \chi_{c1}$. No significant signal is observed, and an upper limit of $\mathcal{B}(\chi_{c1}\to\pi^+\pi^-\eta_c)$ is determined to be $3.1 times 10^{-4}$~at 90\% confidence level, which is one order of magnitude more stringent than the previous measurement.