Observation of sizeable ωcontribution to χc1ð3872Þ→π+ π−J=ψdecays

Resonant structures in the dipion mass spectrum from χc1ð3872Þ→πþπ−J=ψdecays, produced via Bþ→Kþχc1ð3872Þdecays, are analyzed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. A sizeable contribution from the isospin conserving χc1ð3872Þ→ωJ=ψdecay is established for the first time, ð21.4 2.3 2.0Þ%, with a significance of more than 7.1σ. The amplitude of isospin violating decay, χc1ð3872Þ→ρ0J=ψ, relative to isospin conserving decay, χc1ð3872Þ→ωJ=ψ, is properly determined, and it is a factor of 6 larger than expected for a pure charmonium state.