Constrain the UT angle $\gamma$ by CP violation parameters in $B^0 \to \pi^+ \pi^-$

TL;DR

This paper constrains the UT angle gamma using CP violation parameters in B0 to pi+ pi- decays, employing perturbative QCD calculations to analyze decay amplitudes and account for theoretical uncertainties.

Contribution

It provides a novel constraint on the UT angle gamma by combining perturbative QCD calculations with experimental CP violation measurements in B0 to pi+ pi- decays.

Findings

Gamma constrained to 53°–70° range

Estimated 30% U-spin breaking effect

Calculated decay amplitudes with theoretical uncertainties

Abstract

We calculate the tree and penguin amplitudes in the $B^0\to\pi^+\pi^-$ decay channel employing the perturbative QCD factorization approach. Using the amplitudes as input with the theoretical uncertainties sufficiently considered, we constrain the UT angle $\gamma$ to $53^\circ\leq\gamma\leq70^\circ$, from the measurements of the CP violation parameters $C_{\pi^+\pi^-}$ and $S_{\pi^+\pi^-}$ in $B^0\to\pi^+\pi^-$. The U-spin breaking effect between $B^0\to\pi^+\pi^-$ and $B_s^0\to K^+K^-$ is estimated to be around 30\%.