Observation of the $\Lambda_b^0 \to J/\psi \Xi^- K^+$ and $\Xi_b^0 \to J/\psi \Xi^- \pi^+$ decays

TL;DR

This paper reports the first observation of the decay ^0 a0 o J/  ^- ^+ and provides the most precise measurement of the branching fraction of ^0 a0 o J/  ^- ^+ a0 , using LHCb data from 2016-2018 at 13 TeV.

Contribution

The paper presents the first observation of a specific ^0 decay and refines the measurement of another decay's branching fraction using LHCb data.

Findings

First observation of ^0 a0 o J/  ^- ^+ decay.

Most precise measurement of ^0 a0 o J/  ^- ^+ branching fraction.

Branching fraction ratios measured with statistical and systematic uncertainties.

Abstract

The first observation of the $\Xi_b^0 \to J/\psi \Xi^- \pi^+$ decay and the most precise measurement of the branching fraction of the $\Lambda_b^0 \to J/\psi \Xi^- K^+$ decay are reported, using proton-proton collision data from the LHCb experiment collected in 2016--2018 at a centre-of-mass energy of 13~TeV, corresponding to an integrated luminosity of 5.4~fb$^{-1}$. Using the $\Lambda_b^0 \to J/\psi \Lambda$ and $\Xi_b^0 \to J/\psi \Xi^-$ decays as normalisation channels, the ratios of branching fractions are measured to be: \[ \frac{\mathcal{B}(\Lambda_b^0 \to J/\psi \Xi^- K^+)}{\mathcal{B}(\Lambda_b^0 \to J/\psi \Lambda)} = (1.17 \pm 0.14 \pm 0.08)\times 10^{-2} \, , \] \[ \frac{\mathcal{B}(\Xi_b^0 \to J/\psi \Xi^- \pi^+)}{\mathcal{B}(\Xi_b^0 \to J/\psi \Xi^-)} = (11.9 \pm 1.4 \pm 0.6)\times 10^{-2}\, , \] where the first uncertainty is statistical and the second systematic.