Supergravity and Two-Field Inflation Effects in Right-Handed Sneutrino-Modified D-term Inflation

We extend previous work on the minimal D-term inflation model modified by Right-Handed (RH) sneutrino fields to include additional inflaton-sector SUGRA corrections and two-field inflation effects. We show that SUGRA corrections simultaneously allow n_{s} to be within 3-year WMAP limits and the cosmic string contribution to the CMB power spectrum to be less than 5%. For gauge coupling g < 1, the CMB contribution from cosmic strings is predicted to be at least 1% while the spectral index is predicted to be less than 0.968 for a CMB string contribution less than 5%. Treating the inflaton-RH sneutrino system as a two-field inflation model, we show that the time-dependence of the RH sneutrino field strongly modifies the single-field results for values of RH sneutrino mass m_{\Phi} > 0.1 H. The running spectral index is \alpha = -0.0002 when m_{\Phi} < 0.1 H but increases to positive values as m_{\Phi}/H increases, with \alpha > 0.008 for m_{\Phi} > 1.0 H.