Amplitude analysis and branching fraction measurement of $B⁺→ D*-D⁺ₛπ⁺$ decays

The decays of the B⁺ meson to the final state D*-D⁺ₛπ⁺ 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⁺ₛπ⁺ and B⁰→ D*-D⁺ₛ 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*+ₛ→ D⁺ₛγ and D⁺ₛπ⁰ decays, the ratio of branching fractions between the B⁺→ D*-D*+ₛπ⁺ and B⁺→ D*-D⁺ₛπ⁺ decays is determined as 1.31± 0.07± 0.14. An amplitude analysis of the B⁺→ D*-D⁺ₛπ⁺ decay is performed for the first time, revealing dominant contributions from known excited charm resonances decaying to the D*-π⁺ final state. No significant evidence of exotic contributions in the D⁺ₛπ⁺ or D*-D⁺ₛ channels is found. The fit fraction of the scalar state Tcs̄ 0^(2900)⁺⁺ observed in the B⁺→ D⁻D⁺ₛπ⁺ decay is determined to be less than 2.3% at a 90% confidence level.