Measurement of the ratio of branching fractions B(B+c → B0s π+)/B(B+c → J/ψπ+)

The ratio of branching fractions of B+c → B0s π+ and B+c → J/ψπ+ decays is
measured with proton-proton collision data of a centre-of-mass energy of 13 TeV. The data were collected with the LHCb experiment during 2016–2018, corresponding to an integrated luminosity of 5.4 fb−1. The B0s mesons are reconstructed via the decays B0s → J/ψφ and B0s → D−s π+. The ratio of branching fractions is measured to be B(B+c → B0s π+)/B(B+c →J/ψπ+) = 91±10±8±3 where the first uncertainty is statistical, the second is systematic and
the third is due to the knowledge of the branching fractions of the intermediate state decays.