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

TL;DR

This paper reports the first measurement of the quark coupling strength |V_{ub}| using baryonic decays, providing a novel approach that aligns with previous exclusive measurements and highlights discrepancies with inclusive methods.

Contribution

It introduces a new method to determine |V_{ub}| via baryonic decays, expanding the experimental techniques in quark flavor physics.

Findings

First |V_{ub}| measurement using baryonic decays.

Results agree with previous exclusive decay measurements.

Confirms discrepancy with inclusive decay measurements.

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 $\Lambda^0_b$ 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.