# Isospin symmetry breaking effects for the mode ${B}\rightarrow \pi\pi(K)$ in Perturbative QCD

## TL;DR

This paper investigates how isospin symmetry breaking, due to quark mass differences and electroweak effects, influences direct CP violation in specific B meson decays within the perturbative QCD framework, aligning with experimental data.

## Contribution

It introduces a calculation of isospin symmetry breaking effects on CP violation in B decays using the perturbative QCD approach, highlighting the impact of these tiny effects on strong phases.

## Key findings

- Isospin symmetry breaking affects CP violation at leading order.
- Results are consistent with experimental measurements.
- Comparison shows differences with other QCD schemes.

## Abstract

We calculate the direct $CP$ violation for the decay process of ${B}^{0}\rightarrow \pi^{0}\pi^{0}$, ${B}^{+}\rightarrow \pi^{0}\pi^{+}$, ${B}^{0}\rightarrow K^{0}\pi^{0}$ and ${B}^{+}\rightarrow K^{+}\pi^{0}$ via isospin symmetry breaking effects from the $\pi^{0}-\eta-\eta'$ mixing mechanism in perturbative QCD approach. Isospin symmetry breaking originates from the electroweak interaction and the u-d quark mass difference through the strong interaction which are known to be tiny. However, we find that isospin symmetry breaking at the leading order changes the $CP$ violation from the new strong phases. Our calculation results for the $CP$ violation are within or including the range of experimental results. We also compare our results with those from the QCD factorization and the perturbative QCD schemes without regard to isospin symmetry breaking effects.