Observation and Polarization Measurement of B0 --> a1(1260)+ a1(1260)- Decay

TL;DR

This paper reports the measurement of the branching fraction and polarization of B0 decays into a1(1260) pairs using data from the BaBar detector, providing insights into decay dynamics and polarization states.

Contribution

First measurement of B0 -> a1(1260)+ a1(1260)- decay branching fraction and polarization using a large data sample from BaBar.

Findings

Branching fraction times squared a1(1260) decay probability: (11.8 ± 2.6 ± 1.6) x 10^{-6}

Longitudinal polarization fraction fL: 0.31 ± 0.22 ± 0.10

Decay observed with 5.0 sigma significance

Abstract

We present measurements of the branching fraction B and the longitudinal polarization fraction fL for B0 -> a1(1260)+ a1(1260)- decays, with a1(1260)+/- -> \pi- \pi+ \pi+/-. The data sample, collected with the detector BaBar at the SLAC National Accelerator Laboratory, represents 465 10^6 produced BBbar pairs. We measure B(B0 -> a1(1260)+ a1(1260)-) x [B(a1(1260)+ -> \pi- \pi+ \pi+)]^2 = (11.8 \pm 2.6 \pm 1.6) 10^{-6} and fL = 0.31 \pm 0.22 \pm 0.10, where the first uncertainty is statistical and the second systematic. The decay mode is measured with a significance of 5.0 standard deviations including systematic uncertainties.