Direct CP violation in D-meson decays

Recently, the LHCb and CDF collaborations reported a surprisingly large difference between the direct CP asymmetries, Delta A_CP, in the D0 -> K+ K- and D0 -> pi+ pi- decay modes. An interesting question is whether this measurement can be explained within the standard model. In this review, I would like to convey two messages: First, large penguin contractions can plausibly account for this measurement and lead to a consistent picture, also explaining the difference between the decay rates of the two modes. Second, “new physics” contributions are by no means excluded; viable models exist and can possibly be tested.