Physical Review Letters 100,22 (2008)
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 D-0 -> K+pi(-) and (D) over bar (0)-> K+pi(-). Using 281 pb(-1) of e(+)e(-) collision data collected with the CLEO-c detector at E-cm=3.77 GeV, as well as 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. By further including other mixing parameter measurements, 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.
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