Abstract

We study the current estimates of Bc→ Bsπ to extract the fragmentation fraction fc/ fs at the LHCb. A rather robust estimate of Br(Bc→ Bsπ) 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→ Dπ instead of the theoretical cleaner but more suppressed channel B→ DK . We also find a tension on the predictions of Br(Bc→ J/ ψπ) and Br(Bc→ Bsπ) 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/ ψ) ∼ 0.4 % - 1.7 % would be consistent with the LHCb measurements.