The $b$ quark fragmentation fractions at LHCb and meson decays with heavy quark spectators

Abstract

We study the current estimates of $B_c\to B_s\pi$ to extract the fragmentation fraction $f_c/f_s$ at the LHCb. A rather robust estimate of $Br(B_c\to B_s\pi )$ based on factorization and lattice results for the form factor gives $f_c/f_s\sim 0.056$ with a $16\%$ error. We also revisit the extraction of $f_s/f_d$ using $B\to D\pi$ instead of the theoretical cleaner but more suppressed channel $B\to DK$. We also find a tension on the predictions of $Br(B_c\to J/\psi \pi )$ and $Br(B_c\to B_s\pi )$ considering the measurements of these modes at LHCb, and find that, within a $23\%$ uncertainty, only the lower end of the current prediction range $Br(B_c\to J/\psi )\sim 0.4\%-1.7\%$ would be consistent with the LHCb measurements.

Comments: 11 pages, 2 figures