2003/01/31 by Belle Collaboration, K. Abe, I. Adachi +92 · 3 citations
Physics and Astronomy · #Neutrino Physics Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ex
paper · pdf · doi:10.1103/physrevd.68.012001
published as Phys.Rev.D68:012001,2003 · 26 pages, 13 figures, submitted to Phys. Rev. D
arxiv created 2003/04/03 · openalex publication_date 2003/07/07 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We present an improved measurement of CP-violating asymmetries in B0\ensuremath→\ensuremathπ+\ensuremathπ^\ensuremath- decays based on a 78fb^\ensuremath-1 data sample collected at the \ensuremathΥ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e^\ensuremath- collider. We reconstruct one neutral B meson as a B0\ensuremath→\ensuremathπ+\ensuremathπ^\ensuremath- CP eigenstate and identify the flavor of the accompanying B meson from inclusive properties of its decay products. We apply an unbinned maximum likelihood fit to the distribution of the time intervals between the two B meson decay points. The fit yields the CP-violating asymmetry amplitudes A_\ensuremathπ\ensuremathπ=+0.77\ifmmode±\else\textpm\fi0.27(stat)\ifmmode±\else\textpm\fi0.08(syst) and S_\ensuremathπ\ensuremathπ=\ensuremath-1.23\ifmmode±\else\textpm\fi0.41(stat)_\ensuremath-0.07+0.08(syst), where the statistical uncertainties are determined from the Monte Carlo pseudoexperiments. We obtain confidence intervals for CP-violating asymmetry parameters A_\ensuremathπ\ensuremathπ and S_\ensuremathπ\ensuremathπ based on a frequentist approach. We rule out the CP-conserving case, A_\ensuremathπ\ensuremathπ=S_\ensuremathπ\ensuremathπ=0, at the 99.93% confidence level. We discuss how these results constrain the value of the Cabibbo-Kobayashi-Maskawa (CKM) angle \ensuremathφ2.