Measurement of b hadron production fractions in 7 TeV pp collisions

Measurements of $b$ hadron production ratios in proton-proton collisions at a centre-of-mass energy of 7 TeV with an integrated luminosity of 3 pb${}^{-1}$ are presented. We study the ratios of strange $B$ meson to light $B$ meson production $f_s\mathrm{/}(f_u+f_d)$ and ${\mathrm{\Lambda }}_b^0$ baryon to light $B$ meson production $f_{{\mathrm{\Lambda }}_b}\mathrm{/}(f_u+f_d)$ as a function of the charmed hadron-muon pair transverse momentum $p_T$ and the $b$ hadron pseudorapidity $\eta$, for $p_T$ between 0 and 14 GeV and $\eta$ between 2 and 5. We find that $f_s\mathrm{/}(f_u+f_d)$ is consistent with being independent of $p_{\mathrm{T}}$ and $\eta$, and we determine $f_s\mathrm{/}(f_u+f_d)$ = 0.134$\pm$ 0.004 ${}_{-0.010}^{+0.011}$, where the first error is statistical and the second systematic. The corresponding ratio $f_{{\mathrm{\Lambda }}_b}\mathrm{/}(f_u+f_d)$ is found to be dependent upon the transverse momentum of the charmed hadron-muon pair, $f_{\Lambda_b}/(f_u+f_d)=(0.404\pm 0.017 (stat) \pm 0.027 (syst) \pm 0.105 (Br))\times[1 -(0.031 \pm 0.004 (stat) \pm 0.003 (syst))\times p_T(GeV)]$, where Br reflects an absolute scale uncertainty due to the poorly known branching fraction Br(\Lambda_c^+ \to pK^-\pi^+)$\mathrm{.}Weextracttheratioofstrange$B$mesontolightneutral$B$mesonproduction$f_s/f_d$ by averaging the result reported here with two previous measurements derived from the relative abundances of $\bar{B}s \to D_S^+ \pi ^-$to$\bar{B}^0 \to D^+K^-$and$\bar{B}^0 \to D^+\pi^-$\mathrm{.}Weobtain$f_s/f_d=0.267^{+0.021}{-0.020}$.