The emergence of the ΔU = 0 rule in charm physics

Abstract

Abstract We discuss the implications of the recent discovery of CP violation in two-body SCS D decays by LHCb. We show that the result can be explained within the SM without the need for any large SU(3) breaking effects. It further enables the determination of the imaginary part of the ratio of the ΔU = 0 over ΔU = 1 matrix elements in charm decays, which we find to be (0.65 ± 0.12). Within the standard model, the result proves the non-perturbative nature of the penguin contraction of tree operators in charm decays, similar to the known non-perturbative enhancement of ΔI = 1/2 over ΔI = 3/2 matrix elements in kaon decays, that is, the ΔI = 1/2 rule. As a guideline for future measurements, we show how to completely solve the most general parametrization of the D → P + P − system.