Partial flavor symmetry restoration for chiral staggered fermions - art. no. 114503

We study the leading discretization errors for staggered fermions by first constructing the continuum effective Lagrangian, including terms of O(a(2)) , and then constructing the corresponding effective chiral Lagrangian. The terms of O(a(2)) in the continuum effective Lagrangian completely break the SU(4) flavor symmetry down to the discrete subgroup respected by the latti ce theory. We find, however, that the O(a(2)) terms in the potential of the chiral Lagrangian maintain an SO(4) subgroup of SU(4). It follows that the leading discretization errors in the pion masses are SO(4) symmetric, impl ying three degeneracies within the seven lattice irreducible representation s. These predictions hold also for perturbatively improved versions of the action. These degeneracies are observed, to a surprising degree of accuracy , in existing data. We argue that the SO(4) symmetry does not extend to the masses and interactions of other hadrons (vector mesons, baryons, etc.) or to higher order in a(2). We show how it is possible that, for physical qua rk masses of O(a(2)), the new SO(4) symmetry can be spontaneously broken, l eading to a staggered analogue of the Aoki phase of Wilson fermions. This d oes not, however, appear to happen for presently studied versions of the st aggered action. [S0556-2821(99)06923-4].