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

Abstract

In a covariant quark-diquark model, we investigate the rare decay of $Λ_b \rightarrow n l^+ l^-$ and $Λ_b \rightarrow n γ$ 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 $Br(Λ_b \rightarrow n l^+ l^-)\times 10^{8}$ are $6.79(l=e),~4.08 ~ (l=μ),~2.9 ~(l=τ) $ and the branching ratio $Br(Λ_b \rightarrow γ)\times 10^{7} )=3.69$ in central values of parameters.