Estimates of the isospin-violating $\Lambda_b\rightarrow \Sigma^0 \phi, \Sigma^0 J/\psi$ decays and the $\Sigma-\Lambda$ mixing

TL;DR

This paper predicts extremely rare isospin-violating decays of Lambda_b baryons into Sigma^0 and mesons using perturbative QCD, and highlights the significant impact of Sigma-Lambda mixing on these decay rates, especially for J/psi.

Contribution

It provides the first detailed perturbative QCD predictions for these rare decays and demonstrates the substantial effect of Sigma-Lambda mixing on decay rates.

Findings

Branching ratios are predicted to be around 10^{-8} to 10^{-9}.

Sigma-Lambda mixing can enhance the J/psi decay rate by up to two orders of magnitude.

Asymmetry observables are proposed for future experimental tests.

Abstract

We analyse the two purely isospin-violating decays $\Lambda_b\rightarrow \Sigma^0 \phi$ and $\Lambda_b\rightarrow \Sigma^0 J/\psi$, proceed merely via the exchange topologies, in the framework of perturbative QCD approach. Assuming $\Sigma^0$ baryon belongs to the idealized isospin triplet with quark components of $usd$, the branching ratios of the two decay modes are predicted to be tiny, of the order $10^{-8}-10^{-9}$, leading to a difficulty in observing them. We then extend our study to include the $\Sigma-\Lambda$ mixing.It is found that the mixing has significant effect on the $\Lambda_b\rightarrow \Sigma$ decays, especially it can greatly increase the rate of the $J/\psi$ process, by as much as two orders of magnitude, yield $10^{-7}$, which should be searchable in the future. We also estimate a set of asymmetry observables with and without the mixing effect, which will be tested in coming experiments.