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Free keywords:
High Energy Physics - Experiment, hep-ex
MPINP:
LHCb - Abteilung Hofmann
Abstract:
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.
