オクノ ショウジ   Okuno Shoji
  奥野 祥二
   所属   神奈川大学  工学部 情報システム創成学科
   職種   助教
言語種別 日本語
発行・発表の年月 2003/07
形態種別 学術雑誌
査読 査読あり
標題 Evidence for CP-violating asymmetries in B0→ π+π- decays and constraints on the CKM angle φ2
執筆形態 共著
掲載誌名 Phys. Rev. D 68, 012001 (2003) (15 pages)
著者・共著者 K.Abe,
S.Okuno, et al. [BELLE Collaboration],
概要 K.Abe,
S.Okuno, et al. [BELLE Collaboration],
We present an improved measurement of CP-violating asymmetries in B0→ π+π- decays based on a 78 fb-1 data sample collected at the υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ e- collider. We reconstruct one neutral B meson as a B0→ π+π- 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 Aππ = +0.77 ± 0.27(stat) ± 0.08(syst) and Sππ = -1.23± 0.41(stat) -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 Aππ and Sππ based on a frequentist approach. We rule out the CP-conserving case, Aππ = Sππ = 0, at the 99.93% confidence level. We discuss how these results constrain the value of the Cabibbo-Kobayashi-Maskawa (CKM) angle φ2.