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

摘要

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 Upsilon(4S) resonance with the Belle detector at the asymmetric KEKB accelerator, we reconstruct 202 B0 → &phis; Ks 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 S=0.55+/-0.31statist ical+/-0.06systematic A=0.18+/- 0.20statistical+/-0.0 5systematic; The A term shows the absence of direct CP violation and the S 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.