# $B_s^0 \to \eta^{(\prime)} \eta^{(\prime)}$ decays in the pQCD approach

## TL;DR

This paper calculates branching ratios and CP asymmetries for specific $B_s^0$ decays using the pQCD approach, providing predictions that align with other methods and experimental limits, with small gluonic effects and CP asymmetries.

## Contribution

It presents the first detailed pQCD-based predictions for these $B_s^0$ decay modes, including CP asymmetries and gluonic contributions, and compares them with other approaches and data.

## Key findings

- Branching ratios agree with QCD factorization and experimental limits.
- Gluonic contributions are small, less than 7-18%.
- CP asymmetries are very small, less than 3%.

## Abstract

We calculate the CP averaged branching ratios and CP-violating asymmetries for $B_s^0 \to \eta \eta, \eta \eta^\prime$ and $\eta^\prime \eta^\prime$ decays in the perturbative QCD (pQCD) approach here. The pQCD predictions for the CP-averaged branching ratios are $Br(B_s^0 \to \eta \eta) = \left (14.2^{+18.0}_{-7.5}) \times 10^{-6}$, $Br(B_s^0 \to \eta \eta^\prime)= \left (12.4 ^{+18.2}_{-7.0}) \times 10^{-6}$, and $Br(B_s^0 \to \eta^{\prime} \eta^{\prime}) = \left (9.2^{+15.3}_{-4.9}) \times 10^{-6}$, which agree well with those obtained by employing the QCD factorization approach and also be consistent with available experimental upper limits. The gluonic contributions are small in size: less than 7% for $B_s \to \eta \eta$ and $ \eta \eta^\prime$ decays, and around 18% for $B_s \to \eta' \eta'$ decay. The CP-violating asymmetries for three decays are very small: less than 3% in magnitude.