Measurement of CP-violating asymmetries in D[superscript 0]→π[superscript +]π[superscript -] and D[superscript 0]→K[superscript +]K [superscript -] decays at CDF

Abstract

We report on a measurement of CP-violating asymmetries (ACP) in the Cabibbo-suppressed D[superscript 0]→π[superscript +]π[superscript -] and D[superscript 0]→K[superscript +]K [superscript -] decays reconstructed in a data sample corresponding to 5.9 fb[superscript -1] of integrated luminosity collected by the upgraded Collider Detector at Fermilab. We use the strong decay D[superscript *+]→D[superscript 0]π[superscript +] 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 D[superscript 0]→K[superscript -]π[superscript +] decays with and without a D[superscript *±] tag are used to correct for instrumental effects and significantly reduce systematic uncertainties. We measure ACP(D[superscript 0]→π[superscript +]π[superscript -])=(+0.22±0.24(stat)±0.11(syst))% and A[subscript CP](D[superscript 0]→K[superscript +]K [superscript -] )=(-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 D[superscript 0]→π[superscript +]π[superscript -] and D[superscript 0]→K[superscript +]K [superscript -] decays, the results provide an upper limit to the CP-violating asymmetry in D[superscript 0] mixing, |A[subscript CP][superscript ind](D[superscript 0])|<0.13% at the 90% confidence level.