| We present a measurement of a time-dependent difference between the rate of the weak decay KL, and the rate of its charge-parity (CP) conjugate KL.; In the standard model of particle physics, such CP violation in the weak interactions can be accomodated via the Kobayashi-Maskawa (KM) mechanism, which allows an irreducible complex phase in the weak quark-mixing matrix, which is known as the Cabbibo-Kobayashi-Maskawa (CKM) matrix. This model predicts the measured asymmetry, A(t), to take the form At =GB 0d→J/yK L- GB0d →J/yKL GB0 d→J/YK L+ GB0d →J/YKL =-sin 2f1sin Dmdt ,1 where is a convention-independent combination of CKM matrix elements, and Δ md is the mass difference between the Bd meson mass eigenstates. , also known as β, can be interpreted as one of the three inner angles of the “CKM Unitarity Triangle” or “Bjorken Triangle,” which is the graphical representation of the unitarity condition VudV*ub +VcdV*cb +VtdV*tb =0. 2 Using 78 fb−1 of e +e− collision data, collected with the Belle detector at the KEKB accelerator, we reconstruct 1330 B0 → KL candidates, with an estimated signal purity of 62 ± 3%. Using 1230 of these candidates, we measure sin2f1= 0.77±0.16 statistical ±0.07 systematic. 3 ; KL |
