The Atacama B-mode Search (ABS) is an experiment designed to measure cosmic microwave background (CMB) polarization at large angular scales (ℓ>40). It operated from the ACT site at 5190~m elevation in northern Chile at 145 GHz with a net sensitivity (NEQ) of 41 μKs. It employed an ambient-temperature sapphire half-wave plate rotating at 2.55 Hz to modulate the incident polarization signal and reduce systematic effects. We report here on the analysis of data from a 2400 deg2 patch of sky centered at declination −42∘ and right ascension 25∘. We perform a blind analysis. After unblinding, we find agreement with the Planck TE and EE measurements on the same region of sky. We marginally detect polarized dust emission and give an upper limit on the tensor-to-scalar ratio of r<2.3 (95% cl) with the equivalent of 100 on-sky days of observation. We also present a new measurement of the polarization of Tau A and introduce new methods associated with HWP-based observations.
@article{arxiv.1801.01218,
title = {Results from the Atacama B-mode Search (ABS) Experiment},
author = {Akito Kusaka and John Appel and Thomas Essinger-Hileman and James A. Beall and Luis E. Campusano and Hsiao-Mei Cho and Steve K. Choi and Kevin Crowley and Joseph W. Fowler and Patricio Gallardo and Matthew Hasselfield and Gene Hilton and Shuay-Pwu P. Ho and Kent Irwin and Norman Jarosik and Michael D. Niemack and Glen W. Nixon and Michael Nolta and Lyman A. Page and Gonzalo A. Palma and Lucas Parker and Srinivasan Raghunathan and Carl D. Reintsema and Jonathan Sievers and Sara M. Simon and Suzanne T. Staggs and Katerina Visnjic and Ki-Won Yoon},
journal= {arXiv preprint arXiv:1801.01218},
year = {2018}
}