Measurement of CP-violating asymmetries in D0→π+π- and D0→K+K- decays at CDF

Abstract

We report on a measurement of CP-violating asymmetries (ACP) in the Cabibbo-suppressed D0→π+π- and D0→K+K- decays reconstructed in a data sample corresponding to 5.9 fb-1 of integrated luminosity collected by the upgraded Collider Detector at Fermilab. We use the strong decay D*+→D0π+ to identify the flavor of the charmed meson at production and exploit CP-conserving strong cc̅ pair production in pp̅ collisions. High-statistics samples of Cabibbo-favored D0→K-π+ decays with and without a D*± tag are used to correct for instrumental effects and significantly reduce systematic uncertainties. We measure ACP(D0→π+π-)=(+0.22±0.24(stat)±0.11(syst))% and ACP(D0→K+K-)=(-0.24±0.22(stat)±0.09(syst))%, in agreement with CP conservation. These are the most precise determinations from a single experiment to date. Under the assumption of negligible direct CP violation in D0→π+π- and D0→K+K- decays, the results provide an upper limit to the CP-violating asymmetry in D0 mixing, |ACPind(D0)|<0.13% at the 90% confidence level.