Measurement of time-dependent CP violation asymmetries in neutral B meson decays to phi meson neutral kaon(short)

Abstract

We present measurements of time-dependent CP asymmetry parameters in B⁰ → &phis;K _s transitions. We reconstruct one neutral B meson decaying into a CP eigenstate and use the inclusive information of the remaining particles to determine the avor of the accompanying meson at its decay time. Using a data sample of 492 fb^-1 collected at the ϒ(4S) resonance with the Belle detector at the asymmetric KEKB accelerator, we reconstruct 202 B⁰ → &phis; K_s decay candidates with an estimated signal purity of 81.2% after vertexing, flavor tagging and other good vertex selection. From an unbinned maximum likelihood fit to the proper time interval distribution we obtain [special characters omitted]

The [special characters omitted] term shows the absence of direct CP violation and the [special characters omitted] term is consistent with the current world average of sin 2&phis; ₁ as predicted in the Standard Model, where &phis;₁ is one of the angles of the Unitarity Triangle corresponding to the Cabibbo-Kobayashi-Maskawa matrix.