Projects per year
collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an integrated
luminosity of 3 fb−1. The asymmetries in effective decay widths between D0 and D0 decays, sensitive to
indirect CP violation, are measured to be AΓðKþK−Þ¼ð−0.30 0.32 0.10Þ × 10−3 and AΓðπþπ−Þ ¼
ð0.46 0.58 0.12Þ × 10−3, where the first uncertainty is statistical and the second systematic. These
measurements show no evidence for CP violation and improve on the precision of the previous best
measurements by nearly a factor of two.