S. Ball

2 Measurements of B-0(B)over-bar(0) mixing

We have measured the [ital B][sup 0][ital [bar B]0] mixing probability, [chi][sub [ital d]], using a sample of 965 000 [ital B[bar B]] pairs from [Upsilon](4[ital S]) decays. Counting dilepton events, we find [chi][sub [ital d]]=0.157[plus minus]0.016[plus minus]0.018[sub [minus]0.021][sup +0.028]. Using tagged [ital B][sup 0] events, we find [chi][sub [ital d]]=0.149[plus minus]0.023[plus minus]0.019[plus minus]0.010. The first (second) error is statistical (systematic). The third error reflects a [plus minus]15% uncertainty in the assumption, made in both cases, that charged and neutral [ital B] pairs contribute equally to dilepton events. We also obtain a limit on the [ital CP] impurity in the [ital B][sub [ital d]][sup 0] system, [vert bar]Re([epsilon][sub [ital B]][sup 0])[vert bar][lt]0.045 at 90% C.L.

Measurement of the D -> pipi branching fractions

Using data from CLEO II at the Cornell Electron Storage Ring we provide a new measurement of the branching fraction for [ital D][sup 0][r arrow][pi][sup +][pi][sup [minus]], and we present the first measurements of [ital D][sup 0][r arrow][pi][sup 0][pi][sup 0] and of [ital D][sup +][r arrow][pi][sup +][pi][sup 0], which is due to an isospin changing [Delta][ital I]=3/2 transition. From these data we extract the ratio of isospin amplitudes [vert bar][ital A][sub 2]/[ital A][sub 0][vert bar], and the cosine of the relative phase [delta]=[delta][sub 2][minus][delta][sub 0] between these amplitudes, for [ital D][r arrow][pi][pi] decays. Unlike the situation in kaon decay where [ital A][sub 2] is strongly suppressed, we find [vert bar][ital A][sub 2]/[ital A][sub 0][vert bar]=0.72[plus minus]0.13[plus minus]0.11 and cos[delta]=0.14[plus minus]0.13[plus minus]0.09.