Amplitude analysis and branching fraction measurement of B+ → D∗−D+s π+ decays

The decays of the B⁺ meson to the final state D*⁻Dₛ⁺π⁺ 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*⁻Dₛ⁺π⁺ and B⁰ → D*⁻Dₛ⁺ 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⁺ → Dₛ⁺γ and Dₛ⁺π⁰ decays, the ratio of branching fractions between the B⁺ → D⁻Dₛ⁺π⁺ and B⁺ → D*⁻Dₛ⁺π⁺ decays is determined as 1.31 ± 0.07 ± 0.14. An amplitude analysis of the B⁺ → D*⁻Dₛ⁺π⁺ 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 Dₛ⁺π⁺ or D*⁻Dₛ⁺ channels is found. The fit fraction of the scalar state T_{cs¯0}(2900)⁺⁺* observed in the B⁺ → D⁻Dₛ⁺π⁺ decay is determined to be less than 2.3% at a 90% confidence level