Talk presented by Roberto Frezzotti

Parallel Session: Theoretical Developments II

Friday July 2nd, 14.50 - 15.10, Room 8

Authors: Work in collaboration with P. A. Grassi, S. Sint and P. Weisz

A local formulation of lattice QCD without unphysical fermion zero modes

Abstract: The long standing problem of unphysical zero modes, which affects the lattice QCD with Wilson fermions and e.g. shows up with exceptional configurations in quenched studies, can be solved in a clean way by adding to the standard two-flavours Lagrangian a term with a new mass parameter that is coupled to the operator $i \bar{\psi} \gamma_5 \tau^3 \psi$. Exploiting reparametrization invariance under non-singlet chiral transformations, we argue that the continuum limit of the above lattice theory is equivalent to the continuum limit of the standard Wilson lattice QCD, with a natural re-interpretation of observables. Moreover, the O(a) on-shell improvement program can be formulated and carried over similarly to the case of Wilson lattice QCD. In practice, the whole relevant information of QCD can be extracted by simulating the lattice theory with an $i \bar{\psi} \gamma_5 \tau^3 \psi $ term in the Lagrangian, with possible simplications in specific problems of phenomenological interest.

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