研究者情報 | 神奈川大学

オクノ　ショウジ Okuno Shoji 奥野　祥二所属神奈川大学情報学部システム数理学科職種助教
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 A_ππ = +0.77 ± 0.27(stat) ± 0.08(syst) and S_ππ = -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 A_ππ and S_ππ based on a frequentist approach. We rule out the CP-conserving case, A_ππ = S_ππ = 0, at the 99.93% confidence level. We discuss how these results constrain the value of the Cabibbo-Kobayashi-Maskawa (CKM) angle φ₂.