CPviolation in charmed-particle decays

Abstract

The discovery of hadrons bearing new quantum numbers ("charm," collectively) would open up new possibilities to pursue the issue of $\mathrm{CP}$ violation. The matter of $\mathrm{CP}$ signatures for charm-changing processes is discussed in general, model-independent terms save for the assumption that $\frac{\Delta C}{\Delta Q}=1\mathrm{}$ in semileptonic channels. We note certain qualitative differences in the analysis, as compared to charm-conserving reactions. We then raise the issue of indirect effects of $\mathrm{CP}$ violation in charm-changing interactions on the neutral $K$-meson system. In particular an example is discussed in which $\mathrm{CP}$ symmetry breakdown is located in the charm-changing interactions and in which the present $\mathrm{CP}$ evidence for charm-conserving decays is qualitatively accommodated. The operational distinctions between this mechanism and another interesting possibility, the presence of a "second" superweak interaction (one with $\left|\Delta C\right|=2\mathrm{}$), turn out to be delicately linked to $\mathrm{CP}$ tests for exclusive decay processes.