Abstract

We study the current estimates of Bc? Bs? to extract the fragmentation fraction fc/ fs at the LHCb. A rather robust estimate of Br(Bc? Bs?) based on factorization and lattice results for the form factor gives fc/ fs? 0.056 with a 16% error. We also revisit the extraction of fs/ fd using B? D? instead of the theoretical cleaner but more suppressed channel B? DK . We also find a tension on the predictions of Br(Bc? J/ ??) and Br(Bc? Bs?) considering the measurements of these modes at LHCb, and find that, within a 23% uncertainty, only the lower end of the current prediction range Br(Bc? J/ ?) ? 0.4 % - 1.7 % would be consistent with the LHCb measurements. © 2023, The Author(s).