# Resolving the $\phi_2$ ($\alpha$) ambiguity in $B^0 \to a_1^\pm \pi^\mp$

## TL;DR

This paper proposes a novel method to measure the CP-violating phase phi_2 without ambiguity by exploiting interference effects in B meson decays, enabling more precise determination with current experimental data.

## Contribution

It introduces an alternative approach using interference between B to AP and B to VV decays to resolve the phi_2 ambiguity with minimal theoretical assumptions.

## Key findings

- Potential to extract a single phi_2 solution in [0, π] range
- Method can constrain non-factorisable SU(3)-breaking effects
- Achieves similar precision with existing LHCb and Belle II data

## Abstract

I propose an alternative method for measuring the $CP$ violating phase $\phi_2$ ($\alpha$) without ambiguity in an extended SU(3) flavour symmetry analysis, which can ultimately be achieved by exploiting interference effects between $B \to AP$ and $B \to VV$ decay channels, where $A, V, P$ indicates an axial-vector, vector and pseudo-scalar meson, respectively. Under certain assumptions on the relevant decays based on current experimental results and minimal theoretical input, I demonstrate with an idealised amplitude model that a programme to extract a single solution for $\phi_2$ in the range [0,$\pi$], with the added possibility to simultaneously constrain non-factorisable SU(3)-breaking effects, could be executed to similar precision using Run 3 data at LHCb and the final Belle II sample.