A Measurement of the CMB 〈EE〉 Spectrum from the 2003 Flight of BOOMERANG

We report measurements of the CMB polarization power spectra from the 2003 January Antarctic flight of BOOMERANG. The primary results come from 6 days of observation of a patch covering 0.22% of the sky centered near R.A.=82.5d, decl.=-45deg. The observations were made using four pairs of polarization-sensitive bolometers operating in bands centered at 145 GHz. Using two independent analysis pipelines, we measure a nonzero <EE> signal in the range 201<l<1000 with a significance of 4.8 ?, a 2 ? upper limit of 8.6 ?K2 for any <BB> contribution, and a 2 ? upper limit of 7.0 ?K2 for the <EB> spectrum. Estimates of foreground intensity fluctuations and the nondetection of <BB> and <EB> signals rule out any significant contribution from Galactic foregrounds. The results are consistent with a ?CDM cosmology seeded by adiabatic perturbations. We note that this is the first detection of CMB polarization with bolometric detectors.