High-Statistics Study of the tau^- -> pi^- pi⁰ nu_tau Decay

2008/05/31 by M. Fujikawa, H. Hayashii, S. Eidelman · 1 citation
Physics and Astronomy · #hep-ex

paper · pdf · doi:10.1103/physrevd.78.072006

published as Phys.Rev.D78:072006,2008 · 38 pages, 12 figures, matches PRD version

arxiv created 2008/10/29 · arxiv updated 2019/08/13

Abstract

We report a high-statistics measurement of the branching fraction for tau^- --> pi^- pi⁰ nu_tau and the invariant mass spectrum of the produced pi^- pi⁰ system using 72.2 fb^-1 of data recorded with the Belle detector at the KEKB asymmetric-energy e⁺ e^- collider. The branching fraction obtained is (25.24 +/- 0.01 +/- 0.39)%, where the first error is statistical and the second is systematic. The unfolded pi^- pi⁰ mass spectrum is used to determine resonance parameters for the rho(770), rho'(1450), and rho"(1700) mesons. We also use this spectrum to estimate the hadronic (2pi) contribution to the anomalous magnetic moment of the muon (a_mu^pipi). Our result for a_mu^pipi integrated over the mass range sqrts = 2m_pi - 1.8 GeV/c² is a_mu^pipi = (523.5 +/- 1.5 (exp) +/- 2.6 (Br) +/- 2.5 (isospin))x 10^-10, where the first error is due to the experimental uncertainties, the second is due to the uncertainties in the branching fractions and the third is due to the uncertainties in the isospin-violating corrections.

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