Charm mixing

Expectations for the mixing parameter range from to in the Standard Model[53]. Based on our present experience with CLEO II, we expect that sensitivities below will be achieved with CLEO III. The most obvious method to detect such mixing is by observing the decay chain . The sign of the from the decay tags the decay as either a or ; then the sign of the indicates whether the has mixed before decaying. The main background comes from doubly Cabibbo-suppressed decays of the with a rate proportional to tan=0.003, which is measured to be much larger than the mixing signal[54]. Nevertheless, a good measurement of the time dependence should easily separate the two processes. The conventional doubly Cabibbo-suppressed decays should follow a while for mixed events the distribution is

This measurement relies heavily on the vertexing capabilities of the silicon detector, on the angular resolution of the slow , and on good separation. A large value of the mixing parameter would indicate physics beyond the Standard Model.