$CP$-violating lifetime asymmetries of prompt two-body charm decays at LHCb

Asymmetries in the time-dependent rates of ${D}^{0} \rightarrow {K}^{+} {K}^{-}$ and ${D}^{0} \rightarrow \mathrm{\pi}^{+} \mathrm{\pi}^{-}$ decays are measured in a $pp$ collision data sample collected by the $\mbox{LHCb}$ detector during $\mbox{LHC}$ Run 1, corresponding to an integrated luminosity of $3{\,fb}^{-1}$. The asymmetries in effective decay widths between ${D}^{0}$ and ${\kern 0.2em\overline{\kern -0.2em D}{}}{}^{0}$ decays, sensitive to indirect $CP$ violation, are measured to be $A_{\Gamma} ({K}^{+} {K}^{-}) = (-0.30 \pm 0.32 \pm 0.10)\times 10^{-3}$ and $A_{\Gamma}(\mathrm{\pi}^{+} \mathrm{\pi}^{-}) = (0.46 \pm 0.58 \pm 0.12)\times 10^{-3}$, where the first uncertainty is statistical, and the second systematic. These measurements show no evidence of CP violation and improve on the precision of the previous best measurements by nearly a factor of two.