New measurements of B⁺c decays into single charm final states

Using proton-proton collision data corresponding to an integrated luminosity of 9 \,fb⁻¹ collected by the LHCb experiment, searches are performed for B⁺c mesons decaying to a charm and a charmless meson pair. Five products of branching fraction, B(B⁺c\!→ DX), and fragmentation ratio fc/fᵤ are reported, {align*} R_{D^+ K*0} &= ( 1.42 ± 0.23 ± 0.07 ± 0.11 ) × 10⁻⁶, \\ R_{D*0 K^+} &= (1.46 ± 0.30 ± 0.11 ± 0.05 ) × 10⁻⁶, \\ RD^+_s ϕ\ \ \ &= ( 4.0± 1.3 ± 0.2 ± 0.5) × 10⁻⁷, \\ RD^0 K^+\ &= ( 9.7 ± 1.0 ± 0.4 ± 0.3 ) × 10⁻⁷, \\ RD^0 π^+\ &<\ 1.4 × 10⁻⁷\ at 95% CL. {align*} In each case, the first uncertainty is statistical, the second is systematic and the third includes external uncertainties. The first result is a first observation, the second and third exhibit clear evidence and the fourth improves the precision of previous measurements by a factor two. Additionally, the $CP$ asymmetry in B⁺c\!→ D⁰ K⁺ decays is measured and found to be compatible with zero.