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

The decays of the B+ meson to the final state D∗−D+s 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∗−D+s π+ 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+s γ and D+s π0 decays, the ratio of branching fractions between the B+ → D∗−D∗+s π+ and B+ → D∗−D+s π+ decays is determined as 1.31 ± 0.07 ± 0.14. An amplitude analysis of the B+ → D∗−D+
s 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 D+s π+ orD∗−D+s channels is found. The fit fraction of the scalar state T ∗ c¯s0(2900)++ observed in the B+ → D−D+s π+ decay is determined to be less than 2.3% at a 90% confidence level.