2001 Measuring D 0 – D 0 Mixing and Relative Strong Phases

We propose a set of measurements at a charm factory to determine the D– D 0 mixing parameters ∆M and ∆Γ and the strong phase difference δ between doubly-Cabibbo-suppressed (DCS) and Cabibbo-favored (CF) neutral D decays into Kπ. The method can also be used to measure strong phase differences between other corresponding DCS and CF amplitudes. These phase differences are important for studies of D–D 0 mixing. The time development of decays of neutral D mesons to doubly-Cabibbo-suppressed (DCS) modes such as Kπ exhibits interesting behavior. At t = 0 the only term in the amplitude is the direct DCS D → Kπ term, but for t > 0 a D0–D mixing contribution appears. The interference of this term with the DCS contribution involves the lifetime and mass differences of the neutral D mass eigenstates as well as the finalstate strong phase difference δ between the Cabibbo-favored (CF) D 0 → Kπ and DCS D → Kπ decay amplitudes. A recent study of this process by the CLEO Collaboration [1], when combined with direct measurements of the lifetime difference between CP-even and CP-odd neutral D mesons [2, 3, 4, 5, 6], suggests that this strong phase difference may be large [7]. The FOCUS Collaboration has also presented data in agreement with CLEO’s results To be submitted to Physics Letters B.