S. Bertolini et M. Fabbrichesi, Lattice matrix elements confronting the experimental value of epsilon '/epsilon, J HIGH EN P, (10), 1999, pp. NIL_186-NIL_193
A new lattice estimate of K --> 2 pi transitions claims, contrary to all ot
her computations, that the hadronic matrix element for the gluon penguin op
erator Q(6) has opposite sign and, in addition, is much larger than the vac
uum saturation approximation. We comment under what conditions (if any) it
is possible to reconcile this lattice result with the experimental value of
epsilon'/epsilon. The dramatic impact of new physics in the kaon system th
at seems to be required is not easily accommodated within our present theor
etical understanding.