Talk presented by Leonardo Giusti

Tuesday June 29th, 17.20 - 17.40, Auditorium

Matrix elements of $\Delta F =2$ and $\Delta I=3/2$ four-fermion operators without quark masses.

Abstract: Matrix elements of $\Delta F =2$ and $\Delta I=3/2$ four-fermion operators for the full basis have been computed. We have used a new parametrization of the matrix elements which does not involve quark masses and thus allows a reduction of the systematic uncertainty. Moreover, in order to simplify the matching between the lattice and the continuum renormalization schemes, we express our final results in terms of the Renormalization Group Invariant $B$-parameters for all operators which mix under renormalization. The calculation has been performed using the tree-level improved Clover action at two different values of the strong coupling constant (beta=6/g^2=6.0 and 6.2), in the quenched approximation. The renormalization constants and mixing coefficients of the lattice operators have been obtained non-perturbatively. These results improve the accurancy of the phenomenological analysis of the $K^0-\overline{K}^0$, $D^0-\overline{D}^0$ and $B^0-\overline{B}^0$ mixing and $\epsilon'/\epsilon$.

Massimo Campostrini, campo@mailbox.difi.unipi.it