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 Ginsburg-Landau spirit with fourth degree trinomial potentials in the inflaton field \phi .
We derive explicit formulae and study in detail the spectral index n _ { s } of the adiabatic fluctuations , the ratio r of tensor to scalar fluctuations and the running index dn _ { s } / d \ln 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 \to - \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 trinomial 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 with a moderate quartic coupling yielding as most probable values : n _ { s } \simeq 0.958 , r \simeq 0.055 .
This value for r is within reach of forthcoming CMB observations .