Precise Measurement of B 0 − B 0 Mixing Parameters at the Υ(4S) CLEO Collaboration

We describe a measurement of B0−B0 mixing parameters exploiting a method of partial reconstruction of the decay chains B → Dπ and B → Dρ. Using 9.6 ×106BB pairs collected at the Cornell Electron Storage Ring, we find χd = 0.198 ± 0.013 ± 0.014, |yd| < 0.41 at 95% confidence level, and |Re(ǫB)| < 0.034 at 95% confidence level.