# First observation of the radiative decay $\Lambda_{b}^{0} \to \Lambda \gamma$

## TL;DR

This paper reports the first observation of the radiative decay of a beauty baryon, specifically the $ ext{Lambda}_b^0 o ext{Lambda} ext{gamma}$ decay, measuring its branching fraction using LHCb data at 13 TeV.

## Contribution

The paper provides the first experimental observation and measurement of the branching fraction of the radiative decay of the $ ext{Lambda}_b^0$ baryon, a previously unobserved process.

## Key findings

- First observation of $ ext{Lambda}_b^0 o ext{Lambda} ext{gamma}$ decay.
- Measured branching fraction: $(7.1 imes 10^{-6})$ with uncertainties.
- Established a new decay mode for beauty baryons.

## Abstract

The radiative decay $\Lambda_{b}^{0} \to \Lambda \gamma$ is observed for the first time using a data sample of proton-proton collisions corresponding to an integrated luminosity of $1.7\,fb^{-1}$ collected by the LHCb experiment at a center-of-mass energy of $13\,TeV$. Its branching fraction is measured exploiting the $B^{0} \to K^{*0} \gamma$ decay as a normalization mode and is found to be $\mathcal{B}(\Lambda_{b}^{0} \to \Lambda \gamma)= (7.1 \pm 1.5 \pm 0.6 \pm 0.7) \times 10^{-6}$, where the quoted uncertainties are statistical, systematic and systematic from external inputs, respectively. This is the first observation of a radiative decay of a beauty baryon.