Determination of the strong phase in D0→K+π- Using quantum-correlated measurements

We exploit the quantum coherence between pair-produced D0 and D̄0 in ψ(3770) decays to study charm mixing, which is characterized by the parameters x and y, and to make a first determination of the relative strong phase δ between D0→K+π- and D̄0→K+π-. Using 281pb-1 of e+e- collision data collected with the CLEO-c detector at Ecm=3.77GeV, as well as branching fraction input and time-integrated measurements of RM(x2+y2)/2 and RWSΓ(D0→K+π-)/Γ(D̄0→K+π-) from other experiments, we find cosδ=1.03-0.17+0.31±0.06, where the uncertainties are statistical and systematic, respectively. By further including other mixing parameter measurements, we obtain an alternate measurement of cosδ=1.10±0.35±0.07, as well as xsinδ=(4.4-1.8+2. 7±2.9)×10-3 and δ=(22-12-11+11+9)°. © 2008 The American Physical Society.