On [formula omitted] beyond lowest order in the operator product expansion

Abstract

We analyse the structure of long distance (LD) contributions to the CP-violating parameter ϵK, that generally affect both the absorptive (Γ12) and the dispersive (M12) parts of the K0–K¯0 mixing amplitude. We point out that, in a consistent framework, in addition to LD contributions to ImΓ12, estimated recently by two of us, also LD contributions to ImM12 have to be taken into account. Estimating the latter contributions the impact of LD effects on ϵK is significantly reduced (from −6.0% to −3.6%). The overall effect of LD corrections and of the superweak phase being different from 45° is summarised by the multiplicative factor κϵ=0.94±0.02.