We present an upper limit on the polarization of the Cosmic Microwave Background at 7 degree angular scales in the frequency band between 26 and 36 GHz, produced by the POLAR experiment. The campaign produced a map of linear polarization over the R.A. range 112 degrees - 275 degrees at declination 43degrees. The model-independent upper limit on the E-mode polarization component of the CMB at angular scales l = 2 - 20 is 10 microKelvin (95% confidence). The corresponding limit for the B-mode is also 10 microKelvin. Constraining the B-mode power to be zero, the 95% confidence limit on E-mode power alone is 8 microKelvin.
@article{arxiv.astro-ph/0107013,
title = {A Limit on the Large Angular Scale Polarization of the Cosmic Microwave Background},
author = {Brian G. Keating and Christopher W. O'Dell and Angelica de Oliveira-Costa and Slade Klawikowski and Nate Stebor and Lucio Piccirillo and Max Tegmark and Peter T. Timbie},
journal= {arXiv preprint arXiv:astro-ph/0107013},
year = {2009}
}