Measurements of mixing and indirect $CP$ violation in two-body charm decays at LHCb

The large dataset of charm decays collected by LHCb in the first data-taking period (Run 1) of the Large Hadron Collider (LHC), facilitates precision measurements of charm mixing and of the Charge-Parity ( CP ) symmetry. Of particular interest are two-body decays due to their large branching fractions and the abundance of Cabibbo favoured (CF) control modes, sup- pressed modes and CP eigenstates. The observable A Γ , which is predominantly a measure of indirect CP violation, is accessed through the singly Cabibbo suppressed decays D 0 → K + K − and D 0 → π + π − . The results are A Γ ( K + K − ) = ( − 0 . 30 ± 0 . 32 ± 0 . 10 ) × 10 − 3 and A Γ ( π + π − ) = ( 0 . 46 ± 0 . 58 ± 0 . 12 ) × 10 − 3 , where the first uncertainty is statistical, and the second system- atic. These measurements show no evidence of CP violation and improve on the precision of the previous best measurements by nearly a factor of two. The interference between possible de- cay mechanisms of the doubly Cabibbo suppressed (DCS) D 0 → K + π − and D 0 → K − π + decays gives access to the charm system mixing parameters and provides a test of various CP violation hypotheses. The results are consistent with the no CP violation hypothesis