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A steep drop of the cavity quality factor (Qo) at high electric field has been observed frequently in chemicallypolished and high-pressure-rinsed Saclay cavities, even in the absence of field emission. Three single-cell cavities from Saclay were tested at KEK following electropolishing and high pressure rinsing. This treatment eliminated the steep Qo drop, the quench field increased to an accelerating gradient of more than 30 MV/m with a quality factor above 2x10 10 . No dependence of the quench field on the niobium RRR was observed between RRR = 200 and 320 in electropolished cavities.

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We present a precise measurement of the standard model CP -violation parameter sin 2φ 1 , the direct CP violation parameter |λ|, the lifetimes of charged and neutral B mesons and their ratio, and the B 0 -B 0 mixing parameter ∆m d based on a sample of 152 × 10 6 BB pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. One of two B mesons is fully reconstructed in a CP -eigenstate or a flavor-eigenstate decay channel. The flavor of the accompanying B meson is identified from its decay products. From the distributions of the time interval between the two B meson decay points, we obtain sin 2φ 1 = 0.728 ± 0.056(stat) ± 0.023(syst), |λ| = 1.007 ± 0.041(stat) ± 0.033(syst), τ