Measurement of the Quark Mixing Parameter cos2{phi}{sub 1} Using Time-Dependent Dalitz Analysis of B{sup 0}{yields}D[K{sub S}{sup 0}{pi}{sup +}{pi}{sup -}]h{sup 0}

We present a measurement of the angle {phi}{sub 1} of the Cabibbo-Kobayashi-Maskawa unitarity triangle using a time-dependent Dalitz analysis of D{yields}K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} decays produced in neutral B meson decay to a neutral D meson and a light meson (B{sup 0}{yields}D{sup (*)}h{sup 0}). The method allows a direct extraction of 2{phi}{sub 1} and, therefore, helps to resolve the ambiguity between 2{phi}{sub 1} and {pi}-2{phi}{sub 1} in the measurement of sin2{phi}{sub 1}. We obtain sin2{phi}{sub 1}=0.78{+-}0.44{+-}0.22 and cos2{phi}{sub 1}=1.87{sub -0.53-0.32}{sup +0.40+0.22}. The sign of cos2{phi}{sub 1} is determined to be positive at 98.3% C.L.