Observation of the $\Lambda_\mathrm{b}^0$ $\to$ J/$\psi \Lambda \phi$ decay in proton-proton collisions at $\sqrt{s} =$ 13 TeV

TL;DR

This paper reports the first observation of the decay $ ext{Lambda}_b^0 o J/\psi ext{Lambda} ext{phi}$ in proton-proton collisions at 13 TeV, measuring its branching fraction ratio with high precision.

Contribution

The study provides the first measurement of the branching fraction ratio for $ ext{Lambda}_b^0$ decay to $J/\psi ext{Lambda} ext{phi}$ relative to $ ext{Lambda}_b^0 o ext{psi} ext{Lambda}$, using CMS data at 13 TeV.

Findings

First observation of the decay $ ext{Lambda}_b^0 o J/\psi ext{Lambda} ext{phi}$.

Measured branching fraction ratio: (8.26 ± 0.90 (stat) ± 0.68 (syst) ± 0.11 (branching)) × 10$^{-2}$.

Results improve understanding of bottom baryon decay modes.

Abstract

The observation of the $\Lambda_\mathrm{b}^0$ $\to$ J/$\psi \Lambda \phi$ decay is reported using proton-proton collision data collected at $\sqrt{s} =$ 13 TeV by the CMS experiment at the LHC in 2018, corresponding to an integrated luminosity of 60 fb$^{-1}$. The ratio of the branching fractions $\mathcal{B}(\Lambda_\mathrm{b}^0$ $\to$ J/$\psi \Lambda \phi)$ $/$ $\mathcal{B}(\Lambda_\mathrm{b}^0$ $\to$ $\psi \Lambda)$ is measured to be (8.26 $\pm$ 0.90 (stat) $\pm$ 0.68 (syst) $\pm$ 0.11 $(\mathcal{B}))$ $\times$ 10$^{-2}$, where the first uncertainty is statistical, the second is systematic, and the last uncertainty reflects the uncertainties in the world-average branching fractions of $\phi$ and $\psi$(2S) decays to the reconstructed final states.