A pr 1 99 7 Search for CP Violation in Charged D Meson Decays

We report results of a search for CP violation in the singly Cabibbo-suppressed decays D → KKπ, φπ, K(892)0K+, and πππ based on data from the charm hadroproduction experiment E791 at Fermilab. We search for a difference in the D and D decay rates for each of the final states. No evidence for a difference is seen. The decay rate asymmetry parameters (ACP ), defined as the difference in the D and D decay rates divided by the sum of the decay rates, are measured to be: ACP (KKπ) = −0.014± 0.029, ACP (φπ) = −0.028± 0.036, ACP (K(892)K) = −0.010 ± 0.050, and ACP (πππ) = −0.017 ± 0.042. PACS: 11.30.Er; 12.15.Ji; 13.25.Ft; 14.40.Lb CP violation can be accommodated in the Standard Model (SM) by a complex phase in the Cabibbo-Kobayashi-Maskawa matrix describing the transitions between quarks induced by the charged weak interaction. To date, CP violation has been observed only in the neutral kaon system. It is being actively searched for in B decays, where the effects of CP violation in the SM are expected to be large [1], and in hyperon decays [2]. In contrast to the strange and bottom sectors, the SM predictions of CP violation for charm decays are much smaller [3], making the charm sector a good place to test the SM and to look for evidence of physics beyond the SM [4]. CP violation occurs if the decay rate for a particle differs from its CP conjugate decay rate: Γ(D → f) 6= Γ(D → f). Such an asymmetry requires the interference of at least two independent amplitudes with non-zero relative phase. In D decays, as in K and B decays, there are two classes of CP violation: indirect and direct. In the case of indirect CP violation, the asymmetry is associated with mixing, which can occur only in neutral meson decays. In the case of direct CP violation, final state interactions must induce a strong phase shift and both the strong and weak phases of the two amplitudes must differ. This can occur in both charged and neutral meson decays. In the SM, direct CP-violation asymmetries in D decays are predicted to be largest in