Abe, K.Abe, N.Abe, T.Adachi, I.Aihara, H.Akai, K.Akatsu, M.Akemoto, M.Asano, Y.Aushev, T.Bakich, A.M.Ban, Y.Banas, E.Bay, A.Bedny, I.Behera, P.K.Bizjak, I.Bondar, A.Bozek, A.Bračko, M.Brodzicka, J.Browder, T.E.Casey, B.C.K.Chang, P.Chen, K.-F.Cheon, B.G.Chistov, R.Choi, S.-K.Choi, Y.Choi, Y.K.Danilov, M.Dragic, J.Drutskoy, A.Eidelman, S.Eiges, V.Everton, C.W.Flanagan, J.Fukunaga, C.Furukawa, K.Gabyshev, N.Garmash, A.Gershon, T.Golob, B.Guo, R.Hagner, C.Hara, K.Hastings, N.C.Hasuko, K.Hayashii, H.Hazumi, M.Higuchi, T.Hinz, L.Hojo, T.Hokuue, T.Hoshi, Y.Hou, W.-S.Hsiung, Y.B.Huang, H.-C.Igaki, T.Igarashi, Y.Iijima, T.Ikeda, H.Inami, K.Ishikawa, A.Ishino, H.Itoh, R.Iwasaki, H.Iwasaki, Y.Jang, H.K.Kang, J.S.Kapusta, P.Kataoka, S.U.Katayama, N.Katano, G.Kawai, H.Kawamura, N.Kawasaki, T.Kichimi, H.Kikuchi, M.Kikutani, E.Kim, D.W.Kim, H.J.Kim, H.O.Kim, H.Kim, J.H.Kim, S.K.Kobayashi, S.Korpar, S.Križan, P.Krokovny, P.Kubo, T.Kulasiri, R.Kumar, S.Kuzmin, A.Kwon, Y.-J.Lange, J.S.Leder, G.Lee, S.H.2010-11-052010-11-052010-11-05200310.1103/PhysRevD.68.0120012-s2.0-33751180546https://infoscience.epfl.ch/handle/20.500.14299/56813We present an improved measurement of CP-violating asymmetries in B 0→π+π- decays based on a 78 fb -1 data sample collected at the Y(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 Aππ and Sππ based on a frequentist approach. We rule out the CP-conserving case, A ππ=Sππ=0, at the 99.93% confidence level. We discuss how these results constrain the value of the Cabibbo-Kobayashi-Maskawa (CKM) angle φ2. © 2003 The American Physical Society.text::journal::journal article::research article