First Measurement of the CP-Violating Asymmetries with BABAR

TL;DR

This paper presents the first measurement of CP-violating asymmetries in B0 decays using data from the BABAR detector, providing an initial estimate of sin(2beta) with statistical and systematic uncertainties.

Contribution

It reports the first measurement of time-dependent CP asymmetries in B0 decays at BABAR, using a novel data analysis approach for this purpose.

Findings

Measured sin(2beta) = 0.12 ± 0.37 (stat) ± 0.09 (syst)

Analyzed 120 tagged B0 decay candidates

Utilized data from 9.8 fb-1 collected at the Y(4S) resonance

Abstract

We report on a preliminary measurement of time-dependent CP-violating asymmetries in B0 --> J/psi K0S and B0 --> psi(2S) K0S decays recorded by the BABAR detector at the PEP-II asymmetric B Factory at SLAC. The data sample consisted of 9.0 fb-1 collected at the Y(4S) resonance and 0.8 fb-1 off-resonance. One of the pair of neutral B mesons produced at the Y(4S) was fully reconstructed, while the flavor of the other neutral B meson was tagged at the time of its decay. The value of the asymmetry amplitude, sin(2beta), was determined from a maximum likelihood fit to the time distribution of 120 tagged candidates to be sin(2beta) = 0.12 +- 0.37 (stat.) +- 0.09 (syst.) (preliminary).