Precise measurement of B0−B0 mixing parameters at the ϒ(4S)

Abstract We describe a measurement of B 0 − B 0 mixing parameters exploiting a method of partial reconstruction of the decay chains B →D ∗± π ∓ and B →D ∗± ρ ∓ . Using 9.6 ×10 6 B B pairs collected at the Cornell Electron Storage Ring, we find χd=0.198±0.013±0.014, |yd| | R e(ϵ B )| at 95% confidence level.