Talk presented by Elisabetta Pallante

Parallel Session: Matrix Elements I

Tuesday June 29th, 18.00 - 18.20, Auditorium

The $\Delta I=1/2$ rule in Quenched and Unquenched Chiral Perturbation Theory

Abstract: We calculate $K\to \pi\pi$ matrix elements with $\Delta I = 1/2$ at one loop in quenched and unquenched Chiral Perturbation Theory. In particular, we estimate the modifications of the physical amplitude induced by an {\em unphysical} choice of the kinematics (external particles at rest and degenerate quark masses) in the unquenched case and in the quenched approximation. In the quenched octet matrix element we find ``enhanced finite volume'' contributions which may make numerical estimates of this matrix element unreliable for large volumes.

Valid HTML 3.2!     Massimo Campostrini,   campo@mailbox.difi.unipi.it