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A combined amplitude analysis is performed for the decays B^0→Dover ¯^0Dₒ^+π^- and B^+→D^-Dₒ^+π^+, which are related by isospin symmetry. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV. The full data sample corresponds to an integrated luminosity of 9 fb^-1. Two new resonant states with masses of 2. 908±0. 011±0. 020 GeV and widths of 0. 136±0. 023±0. 013 GeV are observed, which decay to Dₒ^+π^+ and Dₒ^+π^- respectively. The former state indicates the first observation of a doubly charged open-charm tetraquark state with minimal quark content cs[over ¯udover ¯], and the latter state is a neutral tetraquark composed of cs[over ¯uover ¯d] quarks. Both states are found to have spin-parity of 0^+, and their resonant parameters are consistent with each other, which suggests that they belong to an isospin triplet.
Aaij et al. (Thu,) studied this question.