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

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.