Two-body Baryonic $B_{u,d,s}$ and $B_c$ to Charmless Final State Decays

TL;DR

This paper predicts decay rates and CP violations for two-body baryonic B decays using topological amplitude formalism and factorization, aligning with experimental bounds and highlighting potential enhancements from non-factorizable effects.

Contribution

It provides updated predictions for baryonic B decay rates and CP violations, incorporating non-factorizable contributions and asymptotic relations, and discusses null tests of the Standard Model.

Findings

Predicted decay rates satisfy experimental bounds.

Small direct CP violations in penguin modes are SM predictions.

Some decay rates can be enhanced by non-factorizable effects.

Abstract

We study the rates and direct CP violations of two-body baryonic $\bar B_{u,d,s}\to {{\rm\bf B}\overline{\rm\bf B}}'$ and $B^-_c\to{{\rm\bf B}\overline{\rm\bf B}}'$ decays, where the final state baryons include low-lying octet and decuplet baryons. We incorporate topological amplitude formalism and the factorization approach. Asymptotic relations at large $m_b$ are used to simplify decay amplitudes. Using the most up-to-date data on $\bar B^0\to p\bar p$ and $B^-\to\Lambda\bar p$ decay rates as inputs, rates and direct CP violations of $\bar B_{u,d,s}\to {{\rm\bf B}\overline{\rm\bf B}}'$ decays are revised and predicted. It is interesting that the results on rates satisfy all existing experimental bounds and some are close to the bounds. Factorization diagrams contribute to penguin-exchange, exchange, annihilation and penguin-annihilation amplitudes. Although the resulting penguin-exchange factorization amplitudes are sizable, the rest suffer from severe chiral suppression and are sensitive to non-factorizable contributions. The $\bar B_s\to p\bar p$ decay rate predicted in factorization calculation is very rare, but it can be enhanced by including non-factorizable contributions. The case where the rate is enhanced to saturate the present experimental bound is discussed. As annihilation modes $B^-_c\to{{\rm\bf B}\overline{\rm\bf B}}'$ decays from factorization calculation are found to be very rare, but they can be enhanced by including non-factorizable contributions as well. Small direct CP violations of pure penguin modes in $\Delta S=-1$ $\bar B_{u,d,s}\to{{\rm\bf B}\overline{\rm\bf B}}'$ decays are robust predictions of the SM, while vanishing direct CP violations of exchange modes in $\bar B_{u,d,s}\to{{\rm\bf B}\overline{\rm\bf B}}'$ decays and in all $B^-_c\to{{\rm\bf B}\overline{\rm\bf B}}'$ decay modes are null tests of the SM.