CP VIOLATION IN THE D⁰ → π⁺π^- DECAY AT CDF

Abstract

We report a measurement of the CP violating asymmetry in D 0 → π + π - decays using approximately 215,000 decays reconstructed in about 5.94 fb -1 of CDF data. We use the strong D ⋆+ → D 0 π + decay ("D ⋆ tag") to identify the flavor of the charmed meson at production time and exploit CP-conserving strong [Formula: see text] pair-production in [Formula: see text] collisions. Higher statistic samples of Cabibbo-favored D 0 → K - π + decays with and without D ⋆ tag are used to highly suppress systematic uncertainties due to detector effects. The result, A CP (D 0 → π + π - ) = [0.22 ± 0.24 (stat.) ± 0.11 (syst.)]%, is the world's most precise measurement to date and it is fully consistent with no CP violation.