Local four quark operator in K0anti K0 mixing: The vacuum saturation estimate as an upper bound for the matrix element

By computing the imaginary part of the propagator of the local four quark operator, we obtain the upper bound: vertical strokeMvertical strokeidentical<=vertical strokeMvertical stroke+O(1/Nsub(c)2) with an uncertainty (outside the 1/Nsub(c)2 corrections) or order 10%. We show how it can be recovered by Laplace hadronic sum rules. (orig./WL)