Study of the kinematic dependences of $Lambda_b^0$ production in $pp$ collisions and a measurement of the $Lambda_b^0 rightarrow Lambda_c^+ pi^-$ branching fraction

The kinematic dependences of the relative production rates, $f_{Lambda_b^0}/f_d$, of $Lambda_b^0$ baryons and $bar{B}^0$ mesons are measured using $Lambda_b^0 rightarrow Lambda_c^+ pi^-$ and $bar{B}^0 rightarrow D^+ pi^-$ decays. The measurements use proton-proton collision data, corresponding to an integrated luminosity of 1 fb$^{-1}$ at a centre-of-mass energy of 7 TeV, recorded in the forward region with the LHCb experiment. The relative production rates are observed to depend on the transverse momentum, $p_T$, and pseudorapidity, $eta$, of the beauty hadron, in the studied kinematic region $1.5 < p_T < 40$ GeV/$c$ and $2 < eta < 5$. Using a previous LHCb measurement of $f_{Lambda_b^0}/f_d$ in semileptonic decays, the branching fraction $mathcal{B}(Lambda_b^0 rightarrow Lambda_c^+ pi^-) = Big( 4.30 pm 0.03 ,, ^{+0.12}_{-0.11} pm 0.26 pm 0.21 Big) times 10^{-3}$ is obtained, where the first uncertainty is statistical, the second is systematic, the third is from the previous LHCb measurement of $f_{Lambda_b^0}/f_d$ and the fourth is due to the $bar{B}^0 rightarrow D^+ pi^-$ branching fraction. This is the most precise measurement of a $Lambda_b^0$ branching fraction to date.

Measurement of the fragmentation fraction ratio $f_{s}/f_{d}$ and its dependence on $B$ meson kinematics

The relative production rate of $B^{0}_{s}$ and $B^{0}$ mesons is determined with the hadronic decays $B^{0}_{s} rightarrow D^{-}_{s}pi^{+}$ and $B^0 rightarrow D^{-}K^{+}$. The measurement uses data corresponding to 1.0 fb$^{-1}$ of $pp$ collisions at a centre-of-mass energy of $sqrt{s}=7$ TeV recorded in the forward region with the LHCb experiment. The ratio of production rates, $f_{s}/f_{d}$, is measured to be $0.238 pm 0.004 pm 0.015 pm 0.021 $, where the first uncertainty is statistical, the second systematic, and the third theoretical. This is combined with a previous LHCb measurement to obtain $f_{s}/f_{d} = 0.256 pm 0.020$. The dependence of $f_{s}/f_{d}$ on the transverse momentum and pseudorapidity of the $B$ meson is determined using the decays $B^{0}_{s} rightarrow D^{-}_{s}pi^{+}$ and $B^{0} rightarrow D^{-}pi^{+}$. There is evidence for a decrease with increasing transverse momentum, whereas the ratio remains constant as a function of pseudorapidity. In addition, the ratio of branching fractions of the decays $B^{0} rightarrow D^{-}K^{+}$ and $B^{0} rightarrow D^{-}pi^{+}$ is measured to be $0.0822 pm 0.0011 (textrm{stat}) pm 0.0025 (textrm{syst})$.