Measurement of the direct CP -violating parameter ACP in the decay D+ →k-π+π+

Abstract

We measure the direct CP-violating parameter ACP for the decay of the charged charm meson, D+→K-π+π+ (and charge conjugate), using the full 10.4fb-1 sample of pp¯ collisions at s=1.96TeV collected by the D0 detector at the Fermilab Tevatron collider. We extract the raw reconstructed charge asymmetry by fitting the invariant mass distributions for the sum and difference of charge-specific samples. This quantity is then corrected for detector-related asymmetries using data-driven methods and for possible physics asymmetries (from B→D processes) using input from Monte Carlo simulation. We measure ACP=[-0.16±0.15(stat)±0.09(syst)]%, which is consistent with zero, as expected from the standard model prediction of CP conservation, and is the most precise measurement of this quantity to date.