Rates and $CP$ asymmetries of Charmless Two-body Baryonic $B_{u,d,s}$ Decays

TL;DR

This paper analyzes charmless two-body baryonic B decays, extracting amplitudes from recent experimental data, predicting decay rates and CP asymmetries, and highlighting modes sensitive to new physics within the Standard Model framework.

Contribution

It provides the first extraction of tree and penguin amplitudes for these decays and predicts rates and CP asymmetries consistent with existing limits, offering new insights into baryonic B decay dynamics.

Findings

Penguin-tree ratio matches expectations.

Predicted decay rates do not violate experimental limits.

CP asymmetry in certain modes can reach ±50%.

Abstract

With the experimental evidences of $\overline B {}^0\to p \overline{p}$ and $B^-\to\Lambda\overline p$ decays, it is now possible to extract both tree and penguin amplitudes of the charmless two-body baryonic $B$ decays for the first time. The extracted penguin-tree ratio agrees with the expectation. Using the topological amplitude approach with the experimental results on $\overline B {}^0\to p \overline{p}$ and $B^-\to\Lambda\bar p$ decay rates as input, predictions on all other $\overline B_q\to {\cal B} \overline {\cal B}$, ${\cal B} \overline {\cal D}$, ${\cal D} \overline {\cal B}$ and ${\cal D} \overline {\cal D}$ decay rates, where ${\mathcal B}$ and ${\cal D}$ are the low lying octet and decuplet baryons, respectively, are given. It is non-trivial that the results do not violate any existing experimental upper limit. From the analysis it is understandable that why $\overline B {}^0\to p \overline{p}$ and $B^-\to\Lambda\bar p$ modes are the first two modes with experimental evidences. Relations on rates are verified using the numerical results. We note that the predicted $B^-\to p\overline{\Delta^{++}}$ rate is close to the experimental bound, which has not been updated in the last ten years. Direct $CP$ asymmetries of all $\overline B_q\to {\cal B} \overline {\cal B}$, ${\cal B} \overline {\cal D}$, ${\cal D} \overline {\cal B}$ and ${\cal D} \overline {\cal D}$ modes are explored. Relations on $CP$ asymmetries are examined using the numerical results. The direct $CP$ asymmetry of $\overline B {}^0\to p \overline{p}$ decay can be as large as $\pm 50\%$. The $CP$ asymmetries of $\Delta S=-1$ pure penguin modes are constrained to be of few $\%$. These modes are expected to be sensitive to New Physics contributions and are good candidates to be added to the list of the tests of the Standard Model.