Search for the decay $χ_{c1}(3872)\toπ^{+}π^{-}χ_{c1}$

Abstract: Using a data sample corresponding to an integrated luminosity of 10.9 fb$<sup>{-1}$ collected at center-of-mass energies from 4.16 to 4.34 GeV with the BESIII detector, we search for the decay $$\chi_{c1}(3872) \to \pi<sup>{+}\pi<sup>{-}\chi_{c1}$$ in the radiative production $$e^{{+}e^{-}} \to \gamma \chi_{c1}(3872)$$. No significant signal is observed, and the ratio for the branching fraction of $$\chi_{c1}(3872) \to \pi<sup>{+}\pi<sup>{-}\chi_{c1}$$ to $\chi_{c1}(3872) \to \pi<sup>{+}\pi<sup>{-}J/\psi$ is measured as $\mathcal{R}\equiv\frac{\mathcal{B}[\chi_{c1}(3872) \to \pi^{{+}\pi^{{-}\chi_{c1}]}{\mathcal{B}[\chi_{c1}(3872)}} \to \pi^{{+}\pi^{-}} J/\psi]}&lt;0.18$ at 90$\%$ confidence level. The upper limit on the product of the cross section $\sigma[e<sup>{+}e<sup>{-}\to\gamma\chi_{c1}(3872)]$ and the branching fraction $$\mathcal{B}[\chi_{c1}(3872)\to\pi<sup>{+}\pi<sup>{-}\chi_{c1}]$$ at each center-of-mass energy is also given. These measurements favor the non-conventional charmonium nature of the $\chi_{c1}(3872)$ state.