Measurement of the $C\!P$ violation parameter $A_Γ$ in $D^0 \to K^+K^-$ and $D^0 \to π^+π^-$ decays

Abstract

Asymmetries in the time-dependent rates of $D^0 \to K^+K^-$ and $D^0 \to π^+π^-$ decays are measured in a $pp$ collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an integrated luminosity of $3\,\mathrm{fb}^{-1}$. The asymmetries in effective decay widths between $D^0$ and $\overline{D}^0$ decays, sensitive to indirect $CP$ violation, are measured to be $A_Γ(K^+ K^-) = (-0.30 \pm 0.32 \pm 0.10)\times 10^{-3}$ and $A_Γ(π^+π^-) = (0.46 \pm 0.58 \pm 0.12)\times 10^{-3}$, where the first uncertainty is statistical and the second systematic. These measurements show no evidence for $C\!P$ violation and improve on the precision of the previous best measurements by nearly a factor of two.

All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-063.html