Determination of the quark coupling strength $|V_{ub}|$ using baryonic decays

Abstract

In the Standard Model of particle physics, the strength of the couplings of the $b$ quark to the $u$ and $c$ quarks, $|V_{ub}|$ and $|V_{cb}|$, are governed by the coupling of the quarks to the Higgs boson. Using data from the LHCb experiment at the Large Hadron Collider, the probability for the ${\Lambda }_b^0$ baryon to decay into the $p{\mu }^{-}{\overline{\nu }}_{\mu }$ final state relative to the ${\Lambda }_c^{+}{\mu }^{-}{\overline{\nu }}_{\mu }$ final state is measured. Combined with theoretical calculations of the strong interaction and a previously measured value of $|V_{cb}|$, the first $|V_{ub}|$ measurement to use a baryonic decay is performed. This measurement is consistent with previous determinations of $|V_{ub}|$ using $B$ meson decays to specific final states and confirms the existing incompatibility with those using an inclusive sample of final states.

18 pages, 5 figures

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