Measurement of the $D^0-{\overline{D}}^0$ mixing at CDF

Department of Physics, University of Siena and INFN, via Roma 56, 53100, Siena, Italy

^a e-mail: paolo.maestro@pi.infn.it

Abstract

We report on the observation of $D^0-{\overline{D}}^0$ oscillations by measuring the time-dependent ratio of yields for the rare decay D⁰ → K⁺π⁻ to the favored decay D⁰ → K⁻π⁺ at the Collider Detector at Fermilab (CDF). Using 9.6 fb⁻¹ of integrated luminosity of √s = 1.96 TeV $p\overline{p}$ collisions recorded in the full CDF Run II, the signals of 7.6×10⁶ D⁰ → K⁻π⁺ and 33×10³ D⁰ → K⁺π⁻ decays are reconstructed in D^*-tagged events, with proper decay times between 0.75 and 10 mean D⁰ lifetimes. We measure the mixing parameters x′² = (0.08 ± 0.18) × 10⁻³, y′ = (4.3 ± 4.3) × 10⁻³, and R_D = (3.51 ± 0.35) × 10⁻³. Our results are consistent with standard model expectations and similar results from proton-proton collisions and exclude the no-mixing hypothesis with a significance equivalent to 6.1 standard deviations.