CHIRAL-SYMMETRY BREAKING IN QCD - A VARIATIONAL APPROACH

We develop a ''variational mass'' expansion approach, recently introdu ced in the Gross-Neveu model, to evaluate some of the order parameters of chiral symmetry breakdown in QCD. The method relies on a reorganiz ation of the usual perturbation theory with the addition of an arbitra ry quark mass m, whose non-perturbative behaviour is inferred partly f rom renormalization group properties, and from analytic continuation i n m properties. The resulting ansatz can be optimized and in the chira l limit m --> 0 we estimate the dynamical contribution to the ''consti tuent'' masses of the light quarks M(u,d,s); the pion decay constant F -pi and the quark condensate ((q) over bar q).