Observation and polarization measurement of B0→a1(1260)+a1(1260)− decay

Abstract

We present measurements of the branching fraction B and longitudinal polarization fraction f L for B 0 → a 1 ( 1260 ) + a 1 ( 1260 ) − decays, with a 1 ( 1260 ) ± → π − π + π ± . The data sample, collected with the BABAR detector at the SLAC National Accelerator Laboratory, represents 465 × 10 6 produced B ¯¯¯ B pairs. We measure B ( B 0 → a 1 ( 1260 ) + a 1 ( 1260 ) − ) × [ B ( a 1 ( 1260 ) + → π − π + π + ) ] 2 = ( 11.8 ± 2.6 ± 1.6 ) × 10 − 6 and f L = 0.31 ± 0.22 ± 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.