Observation of sizeable $\ddot{I}‰$ contribution to $\ddot{I}{‡}_{c1}(3872)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$ decays

Abstract

Resonant structures in the dipion mass spectrum from $\ddot{I}{‡}_{c1}(3872)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$ decays, produced via $B^{+}\to K^{+}\ddot{I}{‡}_{c1}(3872)$ decays, are analyzed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 $f{b}^{-1}$. A sizeable contribution from the isospin conserving $\ddot{I}{‡}_{c1}(3872)\to \ddot{I}‰J/\ddot{I}ˆ$ decay is established for the first time, $(21.4\pm 2.3\pm 2.0)\%$, with a significance of more than $7.1\ddot{I}ƒ$. The amplitude of isospin violating decay, $\ddot{I}{‡}_{c1}(3872)\to \ddot{I}{}^{0}J/\ddot{I}ˆ$, relative to isospin conserving decay, $\ddot{I}{‡}_{c1}(3872)\to \ddot{I}‰J/\ddot{I}ˆ$, is properly determined, and it is a factor of six larger than expected for a pure charmonium state.

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