Time-Dependent {\boldmath $CP$}-Violating Asymmetry in $B^0\to\rho^0\gamma$ Decays

TL;DR

This paper presents the first measurement of CP-violation parameters in B0 to rho0 gamma decays, using a large data sample from the Belle detector, providing insights into matter-antimatter asymmetry.

Contribution

It reports the first measurement of time-dependent and direct CP-violation parameters in B0 to rho0 gamma decays, expanding understanding of CP violation in radiative B decays.

Findings

Measured CP-violation parameters with statistical and systematic uncertainties.

First experimental determination of CP asymmetry in this decay mode.

Results consistent with Standard Model expectations within uncertainties.

Abstract

We report the first measurement of CP-violation parameters in $B^0\to\rho^0\gamma$ decays based on a data sample of $657\times 10^6 B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The flavor of the $B$ meson is identified from the decay products of the accompanying $B$ meson. We obtain the time-dependent and direct CP-violating parameters, $\cals_{\rhoz\gamma} = -0.83\pm 0.65(stat)\pm 0.18(syst)$ and $\cala_{\rhoz\gamma} = -0.44\pm 0.49(stat)\pm 0.14(syst)$, respectively.