Observation of the B0→D*0K+π− and B0s→D*0K−π+ decays

The first observations of B 0 → ¯ D ∗ ( 2007 ) 0 K + π − and B 0 s → ¯ D ∗ ( 2007 ) 0 K − π + decays are presented, and their branching fractions relative to that of the B 0 → ¯ D ∗ ( 2007 ) 0 π + π − decay are reported. These modes can potentially be used to investigate the spectroscopy of charm and charm-strange resonances and to determine the angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle. It is also important to understand them as a source of potential background in determinations of γ from B + → D K + and B 0 → D K + π − decays. The analysis is based on a sample corresponding to an integrated luminosity of 5.4     fb − 1 of proton-proton collision data at 13 TeV center-of-mass energy recorded with the LHCb detector. The ¯ D ∗ ( 2007 ) 0 mesons are fully reconstructed in the ¯ D 0 π 0 and ¯ D 0 γ channels with the ¯ D 0 → K + π − decay. A novel weighting method is used to subtract background while simultaneously applying an event-by-event efficiency correction to account for resonant structures in the decays