# To the origin of the difference of FSI phases in $B\to\pi\pi$ and $B\to\rho\rho$ decays

## TL;DR

This paper proposes a model where soft rescattering explains the difference in FSI phases between B to pi pi and B to rho rho decays, accounting for observed phase variations and CP asymmetries.

## Contribution

It introduces a dominant soft rescattering FSI model to explain phase differences and CP asymmetries in B meson decays, providing a unified explanation for experimental observations.

## Key findings

- Large FSI phases in B_d→ππ decays
- Smaller FSI phases in B_d→ρρ decays
- Predicted direct CP asymmetries in B_d→ππ decays

## Abstract

The final state interactions (FSI) model in which soft rescattering of low mass intermediate states dominates is suggested. It explains why the strong interaction phases are large in the $B_d\to\pi\pi$ channel and are considerably smaller in the $B_d\to\rho\rho$ one. Direct CP asymmetries of $B_d\to\pi\pi$ decays which are determined by FSI phases are considered as well.