Direct CP violation in D-meson decays

TL;DR

This paper reviews the recent measurements of direct CP violation in D-meson decays, discussing whether the standard model can explain the results or if new physics might be involved.

Contribution

It presents a plausible explanation within the standard model via large penguin contractions and discusses the potential for new physics contributions.

Findings

Large penguin contractions can account for the observed CP asymmetries.

Standard model explanations are plausible for the measurements.

Viable new physics models could also explain the results.

Abstract

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.