The first observation of the $\Lambda_b^0\to D_s^- p$ decay is presented using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of ${ \sqrt{ s}=13 \,\textrm{ TeV}}$, corresponding to a total integrated luminosity of $6\,\textrm{ fb}^{ -1}$. Using the $\Lambda_b^0\to\Lambda_c^+\pi^-$ decay as the normalisation mode, the branching fraction of the $\Lambda_b^0\to D_s^- p$ decay is measured to be ${ \mathcal{ B}(\Lambda_b^0\to D_s^- p)=(12.6 \pm 0.5 \pm 0.3 \pm 1.2 )\times 10^{ -6}}$, where the first uncertainty is statistical, the second systematic and the third due to uncertainties in the branching fractions of the $\Lambda_b^0\to\Lambda_c^+\pi^-$, $D_s^- \to K^-K^+\pi^-$ and $\Lambda_c^+\to p K^- \pi^+$ decays.
Categories: hep-ex