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
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.