  We present a new formulation of Lagrangian perturbation theory which allows
accurate predictions of the real- and redshift-space correlation functions of
the mass field and dark matter halos. Our formulation involves a
non-perturbative resummation of Lagrangian perturbation theory and indeed can
be viewed as a partial resummation of the formalism of Matsubara (2008a,b) in
which we keep exponentiated all of the terms which tend to a constant at large
separation. One of the key features of our method is that we naturally recover
the Zel'dovich approximation as the lowest order of our expansion for the
matter correlation function. We compare our results against a suite of N-body
simulations and obtain good agreement for the correlation functions in
real-space and for the monopole correlation function in redshift space. The
agreement becomes worse for higher multipole moments of the redshift-space,
halo correlation function. Our formalism naturally includes non-linear bias and
explains the strong bias-dependence of the multipole moments of the
redshift-space correlation function seen in N-body simulations.
