Measurement of CP-Violating Asymmetries in $B^0\to(\rho\pi)^0$ Using a Time-Dependent Dalitz Plot Analysis

TL;DR

This paper presents a measurement of CP-violating asymmetries in B0 decays to rho pi using a time-dependent Dalitz plot analysis, providing evidence of direct CP violation and constraining the Unitarity Triangle angle alpha.

Contribution

It introduces a novel time-dependent Dalitz plot analysis method to measure CP violation in B0 to rho pi decays, with results from a large data sample.

Findings

Evidence of direct CP violation at three standard deviations.

Measurement of 26 decay coefficients related to CP asymmetries.

Constraint on the Unitarity Triangle angle alpha.

Abstract

We report a measurement of CP-violating asymmetries in $B^0\to(\rho\pi)^0\to\pi^+\pi^-\pi^0$ decays using a time-dependent Dalitz plot analysis. The results are obtained from a data sample of 347 million $\Upsilon(4S) \to B\bar{B}$ decays, collected by the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. We measure 26 coefficients of the bilinear form factor terms occurring in the time-dependent decay rate of the \Bz meson and derive the physically relevant quantities from these coefficients. In particular we find a three standard deviation evidence of direct CP-violation in $B^0\to\rho^\pm\pi^\mp$ decays, with systematic uncertainties included. We also achieve a constraint of the angle $\alpha$ of the Unitarity Triangle. All results presented are preliminary.