CMB Temperature Polarization Correlation and Primordial Gravitational Waves: WMAP5

we continue our study of the CMB temperature polarization (TE) cross-correlation as a source ofinformation about primordial gravitational waves (PGWs). In a previous paper, we considered twomethods for detecting PGWs using the TE cross-correlation. The first method is the zero multipolemethod, where we find the multipole, ℓ0, where the TE cross-correlation power spectrum, CℓTE, first changes sign. The second method Wiener filters the CMB TE data to remove the densityperturbation contribution to the TE power spectrum. We then use statistical tests to determineif there is a detection of negative residual TE correlation and hence a detection of primordialgravitational waves, the only source of negative TE correlation at these superhorizon scales. In thispaper, we will apply these tests to the WMAP 5-year data. We find that the TE power spectrumconsistent with r < 2.0 at 95% confidence with no additional assumptions about the PGWs. If weassume that the PGWs are generated by inflation, then we get r < 1.0 at 95% confidence