FCNC transitions of $\Lambda_b$ to neutron in Bethe-Salpeter equation approach

TL;DR

This paper studies rare $ ext{Lambda}_b$ baryon decays into a neutron and leptons or a photon using a covariant quark-diquark model with Bethe-Salpeter equations, providing predictions for form factors and branching ratios.

Contribution

It introduces a Bethe-Salpeter equation approach within a covariant quark-diquark model to analyze $ ext{Lambda}_b$ decays, offering new quantitative predictions.

Findings

Form factor ratio R varies from -0.90 to -0.25.

Branching ratios for $ ext{Lambda}_b ightarrow n l^+ l^-$ are of order 10^{-8}.

Branching ratio for $ ext{Lambda}_b ightarrow n \gamma$ is approximately 3.69×10^{-7}.

Abstract

In a covariant quark-diquark model, we investigate the rare decay of $\Lambda_b \rightarrow n l^+ l^-$ and $\Lambda_b \rightarrow n \gamma$ in the Bethe-Salpeter equation approach. In this model the baryons are treated as bound states of a constituent quark and a diquark interacting via a gluon exchange and the linear confinement. We find that the ratio of form factors $R$ is varies from $-0.90$ to $-0.25$ and the branching ratios $Br(\Lambda_b \rightarrow n l^+ l^-)\times 10^{8}$ are $6.79(l=e),~4.08 ~ (l=\mu),~2.9 ~(l=\tau) $ and the branching ratio $Br(\Lambda_b \rightarrow \gamma)\times 10^{7} )=3.69$ in central values of parameters.