CPViolation: Interference Effects inK0Decay

The intrinsic magnitude of the $\mathrm{CP}$-violating coupling is not simply related to the decay ratio $\frac{(K_L\to 2\pi )}{(K_S\to 2\pi )}$, because of the $K_L-K_S$ overlap. It is this intrinsic coupling which is needed to estimate $\mathrm{CP}$ violation in other systems. We examine an explicit model showing the interference effects of the $K_L-K_S$ overlap on the relation of the coupling constants to the above decay ratio. There are interference effects in $\epsilon$ which depend on nonmeasurable mass shifts. (Theoretical estimates of these mass shifts are discussed.) However, ${\epsilon }^{\prime }$ does not depend on these mass shifts and thus can be more easily related to the intrinsic $\mathrm{CP}$-violating coupling.