CP asymmetries in singly-Cabibbo-suppressed D decays to two pseudoscalar mesons

The LHCb Collaboration has recently reported evidence for a CP asymmetry approaching the percent level in the difference between D⁰→π⁺π^- and D⁰→K⁺K^-. We analyze this effect as if it is due to a penguin amplitude with the weak phase of the standard model c→b→u loop diagram, but with a CP-conserving enhancement as if due to the strong interactions. In such a case the magnitude and strong phase of this amplitude P_b are correlated in order to fit the observed CP asymmetry, and one may predict CP asymmetries for a number of other singly-Cabibbo-suppressed decays of charmed mesons to a pair of pseudoscalar mesons. Nonzero CP asymmetries are expected for D⁺→K⁺K¯⁰ (the most promising channel for which a nonzero CP asymmetry has not yet been reported), as well as D⁰→π⁰π⁰, D_s⁺→π⁺K⁰, and D_s→π⁰K⁺. No CP asymmetry is predicted for D⁺→π⁺π⁰ or D⁰→K⁰K¯⁰ in this framework.