Amplitude analysis and branching fraction measurement of B^+ D^*-D^+ₒ^+ decays

The decays of the B^+ meson to the final state D^*-D^+ₒ^+ are studied in proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb^-1. The ratio of branching fractions of the B^+ D^*-D^+ₒ^+ and B^0 D^*-D^+ₒ decays is measured to be 0. 173 0. 006 0. 010, where the first uncertainty is statistical and the second is systematic. Using partially reconstructed D^*+ₒ D^+ₒ and D^+ₒ^0 decays, the ratio of branching fractions between the B^+ D^*-D^*+ₒ^+ and B^+ D^*-D^+ₒ^+ decays is determined as 1. 31 0. 07 0. 14. An amplitude analysis of the B^+ D^*-D^+ₒ^+ decay is performed for the first time, revealing dominant contributions from known excited charm resonances decaying to the D^*-^+ final state. No significant evidence of exotic contributions in the D^+ₒ^+ or D^*-D^+ₒ channels is found. The fit fraction of the scalar state T₂ₒ ₀^ (2900) ^++ observed in the B^+ D^-D^+ₒ^+ decay is determined to be less than 2. 3% at a 90% confidence level.