Determination of the D0→K+π- relative strong phase using quantum-correlated measurements in e+e-→D0(D)over-bar0 at CLEO

We exploit the quantum coherence between pair-produced D-0 and (D) over bar (0) in psi(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 delta between doubly Cabibbo-suppressed D-0 -> K+pi(-) and Cabibbo-favored (D) over bar (0)-> K+pi(-). We analyze a sample of 1.0 x 10(6) D-0(D) over bar (0) pairs from 281 pb(-1) of e(+)e(-) collision data collected with the CLEO-c detector at E-cm=3.77 GeV. By combining CLEO-c measurements with branching fraction input and time-integrated measurements of R-M equivalent to (x(2)+y(2))/2 and R-WS equivalent to Gamma(D-0 -> K+pi(-))/Gamma((D) over bar (0)-> K+pi(-)) from other experiments, we find cos delta = 1.03(-0.17)(+0.31) +/- 0.06, where the uncertainties are statistical and systematic, respectively. In addition, by further including external measurements of charm mixing parameters, we obtain an alternate measurement of cos delta = 1.10 +/- 0.35 +/- 0.07, as well as xsin delta = (4.4(-1.8)(+2.7) +/- 2.9) x 10(-3) and delta = (22(-12-11)(+11+9))degrees.