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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2002, vol. 66, p. -

Observation of mixing-induced CP violation in the neutral B meson system

Abe K., Abe K., Abe R., Abe T., Adachi I., Ahn Byouns Sup, Aihara H., Akatsu M., Asano Y., Aso T., Aushev T., Bakich A. M., Ban Y., Banas E., Behari S., Behera P. K., Bondar A., Bozek A., Bračko M., Browder T. E., Casey B. C K, Chang P., Chao Y., Cheon B. G., Chistov R., Choi S. K., Choi Y., Dong L. Y., Dragic J., Drutskoy A., Eidelman S., Eiges V., Enari Y., Everton C. W., Fang F., Fukunaga C., Fukushima M., Gabyshev N., Garmash A., Gershon T., Golob B., Gordon A., Guler H., Guo R., Haba J., Hamasaki H., Hanagaki K., Handa F., Hara K., Hara T., Hastings N. C., Hayashii H., Hazumi M., Heenan E. M., Higuchi I., Higuchi T., Hojo T., Hokuue T., Hoshi Y., Hou S. R., Hou W. S., Hsu S. C., Huang H. C., Igaki T., Iijima T., Ikeda H., Inami K., Ishikawa A., Ishino H., Itoh R., Iwasaki H., Iwasaki Y., Jackson D. J., Jang H. K., Kakuno H., Kang J. H., Kang J. S., Kapusta P., Katayama N., Kawai H., Kawai H., Kawakami Y., Kawamura N., Kawasaki T., Kichimi H., Kim D. W., Kim Heejong, Kim H. J., Kim H. O., Kim Hyunwoo, Kim S. K., Kim T. H., Kinoshita K., Konishi H., Korpar S.

This article describes an observation of mixing-induced CP violation and a measurement of the CP violation parameter, sin 2φ 1, with the Belle detector at the KEKB asymmetric e +e - collider. Using a data sample of 29.1 fb -1 recorded on the Y(4S) resonance that contains 31.3 million BB̄ pairs, we reconstruct decays of neutral B mesons to the following CP eigenstates: J/ψK s 0, ψ(2S)K s 0, χ c1K s 0 η cK s 0, J/ψK L 0 and J/ψK* 0. The flavor of the accompanying B meson is identified by combining information from primary and secondary leptons, K ± mesons, A baryons, slow and fast pions. The proper-time interval between the two B meson decays is determined from the distance between the two decay vertices measured with a silicon vertex detector. The result sin 2φ 1=0.99±0.14(stat)±0.06(syst) is obtained by applying a maximum likelihood fit to the 1137 candidate events. We conclude that there is large CP violation in the neutral B meson system. A zero value for sin 2φ, 1 is ruled out by more than six standard deviations. © 2002 The American Physical Society.