Measurement of indirect CP-violating asymmetries in $D^0\to K^+K^-$ and $D^0\to \pi^+\pi^-$ decays at CDF

TL;DR

This paper reports a precise measurement of indirect CP-violating asymmetries in $D^0$ meson decays using Fermilab data, finding results consistent with CP symmetry and improving understanding of charm meson behavior.

Contribution

First measurement of $A_ ext{Gamma}$ in $D^0$ decays at Fermilab, using full data set and advanced background subtraction techniques.

Findings

Measured $A_ ext{Gamma}(K^+K^-) = (-0.19 extpm 0.15 extpm 0.04) ext{ extperthousand}$

Measured $A_ ext{Gamma}(\pi^+\pi^-) = (-0.01 extpm 0.18 extpm 0.03) ext{ extperthousand}$

Combined result $A_ ext{Gamma} = (-0.12 extpm 0.12) ext{ extperthousand}$

Abstract

We report a measurement of the indirect CP-violating asymmetries ($A_{\Gamma}$) between effective lifetimes of anticharm and charm mesons reconstructed in $D^0\to K^+ K^-$ and $D^0\to \pi^+\pi^-$ decays. We use the full data set of proton-antiproton collisions collected by the Collider Detector at Fermilab experiment and corresponding to $9.7$~fb$^{-1}$ of integrated luminosity. The strong-interaction decay $D^{*+}\to D^0\pi^+$ is used to identify the meson at production as $D^0$ or $\overline{D}^0$. We statistically subtract $D^0$ and $\overline{D}^0$ mesons originating from $b$-hadron decays and measure the yield asymmetry between anticharm and charm decays as a function of decay time. We measure $A_\Gamma (K^+K^-) = (-0.19 \pm 0.15 (stat) \pm 0.04 (syst))\%$ and $A_\Gamma (\pi^+\pi^-)= (-0.01 \pm 0.18 (stat) \pm 0.03 (syst))\%$. The results are consistent with the hypothesis of CP symmetry and their combination yields $A_\Gamma = (-0.12 \pm 0.12)\%$.