New Limits on the Polarized Anisotropy of the Cosmic Microwave Background at Subdegree Angular Scales

We update the limit from the 90 GHz Princeton IQU Experiment ground-based polarimeter on the magnitude of any polarized anisotropy of the cosmic microwave radiation. With a second year of data, we have now limited both Q and U on a ring of 1° radius. The window functions are broad: for E-mode polarization, the effective l is ⟨lE⟩ = 191. We find that the E-mode signal can be no greater than 8.4 μK (95% CL), assuming no B-mode polarization. Limits on a possible B-mode signal are also presented.