Observation of B0 Meson Decay to a1(1260)+- pi-+

TL;DR

This paper reports the first observation of the B0 meson decay to a1(1260)± pi∓, measuring its branching fraction with high statistical significance using data from the BaBar detector.

Contribution

The study provides the first measurement of the B0 --> a1(1260)± pi∓ decay branching fraction using a large data sample and advanced multivariate analysis techniques.

Findings

Branching fraction measured as (16.6 +/- 1.9 +/- 1.5) x 10^{-6}

Decay observed with 9.2 sigma significance

First observation of this decay mode

Abstract

We present a measurement of the branching fraction of the decay B0 --> a1(1260)^{+-} pi^{-+} with a1(1260)^{+-} --> pi^{-+} pi^{+-} pi^{+-}. The data sample consists of 218 million B B-bar pairs collected at the Y(4S) resonance and recorded by the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC. The analysis is based on unbinned multivariate maximum likelihood fit. The measured branching fraction is: (16.6 +/- 1.9 +/- 1.5) 10^{-6}. The decay mode, observed for the first time, is seen with a significance of 9.2 sigma (systematic uncertainties included).