  We perform a MCMC (Monte Carlo Markov Chains) analysis of the available CMB
and LSS data (including the three years WMAP data) with single field slow-roll
new inflation and chaotic inflation models. We do this within our approach to
inflation as an effective field theory in the GinsburgLandau spirit with fourth
degree trinomial potentials in the inflaton field phi.We derive explicit formu-
lae and study in detail the spectral index ns of the adiabatic fluctuations the
ratio r of tensor to scalar fluctuations and the running index dn_s/dln k. We
use these analytic formulas as hard constraints on n_s and r in the MCMC
analysis.Our analysis differs in this crucial aspect from previous MCMC studies
in the literature involving the WMAP3 data. Our results are as follow: (i) The
data strongly indicate the breaking (whether spontaneous or explicit) of the
phi -> -phi symmetry of the inflaton potentials both for new and for chaotic
inflation.(ii)Trinomial new inflation naturally satisfies this requirement and
provides an excellent fit to the data.(iii)Trinomial chaotic inflation produces
the best fit in a very narrow corner of the parameter space.(iv) The chaotic
symmetric trinomial potential is almost certainly ruled out(at 95% CL).In tri-
nomial chaotic inflation the MCMC runs go towards a potential in the boundary
of the parameter space and which ressembles a spontaneously symmetry broken
potential of new inflation. (v) The above results and further physical analysis
here lead us to conclude that new inflation gives the best description of the
data.(vi) We find a lower bound for r within trinomial new inflation potentials
r > 0.016 (95% CL) and r > 0.049 (68% CL). (vii) The preferred new inflation
trinomial potential is a double well, even function of the field yielding as
most probable values: n_s ~ 0.958, r ~ 0.055. Such r could be observed soon.
