Observation of sizeable ω contribution to χ c1ð3872Þ → π + π − J=ψ decays

Abstract

Resonant structures in the dipion mass spectrum from χc1ð3872Þ → πþπ−J=ψ decays, produced via Bþ → Kþχc1ð3872Þ decays, 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=ψ decay 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.