Observation of D[superscript 0]-[line over D][superscript 0] Mixing Using the CDF II Detector

Abstract

We measure the time dependence of the ratio of decay rates for D[superscript 0] → K[superscript +]π[superscript −] to the Cabibbo-favored decay D[superscript 0] → K[superscript −]π[superscript +]. The charge conjugate decays are included. A signal of 3.3 × 10[superscript 4] D[superscript *+] → π[superscript +]D[superscript 0], D[superscript 0] → K[superscript +]π[superscript −] decays is obtained with D[superscript 0] proper decay times between 0.75 and 10 mean D[superscript 0] lifetimes. The data were recorded with the CDF II detector at the Fermilab Tevatron and correspond to an integrated luminosity of 9.6 fb[superscript −1] for p[line over p] collisions at s√ = 1.96 TeV. Assuming CP conservation, we search for D[superscript 0]-[line over D[superscript 0] mixing and measure the mixing parameters to be R[subscript D] = (3.51 ± 0.35) × 10[superscript −3], y[superscript ′] = (4.3 ± 4.3) × 10[superscript −3], and x[superscript '2] = (0.08 ± 0.18) × 10[superscript −3]. We report Bayesian probability intervals in the x[superscript '2]-y[superscript ′] plane and find that the significance of excluding the no-mixing hypothesis is equivalent to 6.1 Gaussian standard deviations, providing the second observation of D[superscript 0]-[line over D[superscript 0] mixing from a single experiment.