A study of time-dependent CP-violating asymmetries in B0 --> J/psi K0S and B0 --> psi(2S) K0S decays

TL;DR

This paper reports on BABAR's measurement of time-dependent CP asymmetries in B0 decays to J/psi K0S and psi(2S) K0S, using 9.0 fb^-1 of data to estimate sin2beta with a neural network-based event selection.

Contribution

First measurement of sin2beta in these decay channels using a neural network for event selection at BABAR.

Findings

Measured sin2beta = 0.12 ± 0.37 ± 0.09

Reconstructed 168 decay events, with 120 flavor-tagged

Implemented neural network to recover events without clear signatures

Abstract

BABAR has studied the time dependent asymmetries in the the decays B0 -> J/psi K0S and B0 -> psi(2S) K0S in a data set of 9.0 fb^-1 taken at the Y(4S)resonance. In these channels we reconstruct 168 events of which 120 are flavor tagged and used in a likelihood fit where we determine sin2beta. The flavor of the other neutral $B$ mesons is tagged using information primarily from identified leptons and Kaons. A neural network is used to recover events without any clear Kaon or lepton signature. A preliminary result of sin2beta=0.12+/-0.37+/-0.09 is obtained.