Amplitude analysis of the $\ddot{I}{‡}_{c1}\to \hat{I}\cdot \ddot{I}{€}^{+}\ddot{I}{€}^{-}$ decays

Abstract

Using $448.0\times 10^6$~$\ddot{I}ˆ(3686)$ events collected with the BESIII detector, an amplitude analysis is performed for $\ddot{I}ˆ(3686)\to {\hat{I}}^3\ddot{I}{‡}_{c1}$, $\ddot{I}{‡}_{c1}\to \hat{I}\cdot \ddot{I}{€}^{+}\ddot{I}{€}^{-}$ decays. The most dominant two-body structure observed is $a_0(980{)}^{\pm }\ddot{I}{€}^{\mp }$; $a_0(980{)}^{\pm }\to \hat{I}\cdot \ddot{I}{€}^{\pm }$. The $a_0(980)$ line shape is modeled using a dispersion relation, and a significant non-zero $a_0(980)$ coupling to the $\hat{I}{\cdot }^{\prime }\ddot{I}€$ channel is measured. We observe $\ddot{I}{‡}_{c1}\to a_2(1700)\ddot{I}€$ production for the first time, with a significance larger than 17$\ddot{I}ƒ$. The production of mesons with exotic quantum numbers, $J^{PC}=1^{-+}$, is investigated, and upper limits for the branching fractions $\ddot{I}{‡}_{c1}\to \ddot{I}{€}_1(1400{)}^{\pm }\ddot{I}{€}^{\mp }$, $\ddot{I}{‡}_{c1}\to \ddot{I}{€}_1(1600{)}^{\pm }\ddot{I}{€}^{\mp }$, and $\ddot{I}{‡}_{c1}\to \ddot{I}{€}_1(2015{)}^{\pm }\ddot{I}{€}^{\mp }$, with subsequent $\ddot{I}{€}_1(X{)}^{\pm }\to \hat{I}\cdot \ddot{I}{€}^{\pm }$ decay, are determined.

14 pages, 6 figures