Amplitude analysis of the $\Xi^+_c\to pK^-\pi^+$ decay and $\Xi^+_c$ baryon polarization measurement in semileptonic beauty-hadron decays

Abstract

An amplitude analysis of the $\Xi^+_c\to pK^-\pi^+$ decay together with a measurement of the $\Xi^+_c$ polarization vector in semileptonic beauty-hadron decays is presented. The analysis is performed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 ${\rm fb}^{-1}$. An amplitude model is developed and the resonance fractions as well as two- and three-body decay parameters are reported. A sizeable $\Xi^+_c$ polarization is found. A large sensitivity of the $\Xi^+_c\to pK^-\pi^+$ decay to the polarization is seen, making the amplitude model suitable for $\Xi^+_c$ polarization measurements in other systems.