BICEP/Keck XVIII: Measurement of BICEP3 polarization angles and consequences for constraining cosmic birefringence and inflation

Creators: Ade, P. A. R.¹; Ahmed, Z.^{2, 3}; Amiri, M.⁴; Barkats, D.⁵; Basu Thakur, R.⁶; Bischoff, C. A.⁷; Beck, D.⁸; Bock, J. J.^{6, 9}; Boenish, H.⁵; Buza, V.¹⁰; Cheshire, J. R.^{6, 11}; Connors, J.¹²; Cornelison, J.⁵; Crumrine, M.¹¹; Cukierman, A. J.⁸; Denison, E.¹²; Duband, L.¹³; Eiben, M.⁵; Elwood, B. D.¹⁴; Fatigoni, S.⁶; Filippini, J. P.¹⁵; Fortes, A.⁸; Gao, M.⁶; Giannakopoulos, C.⁷; Goeckner-Wald, N.⁸; Goldfinger, D. C.⁸; Grayson, J. A.⁸; Greathouse, A.¹¹; Grimes, P. K.⁵; Hall, G.^{11, 8}; Halal, G.⁸; Halpern, M.⁴; Hand, E.⁷; Harrison, S. A.⁵; Henderson, S.^{2, 3}; Hubmayr, J.¹²; Hui, H.⁶; Irwin, K. D.⁸; Kang, J. H.⁶; Karkare, K. S.^{2, 3}; Kefeli, S.⁶; Kovac, J. M.¹⁴; Kuo, C.⁸; Lau, K.⁶; Lautzenhiser, M.⁷; Lennox, A.¹⁵; Liu, T.⁸; Megerian, K. G.⁹; Minutolo, L.⁶; Moncelsi, L.⁶; Nakato, Y.⁸; Nguyen, H. T.^{9, 6}; O'brient, R.^{9, 6}; Patel, A.⁶; Petroff, M. A.⁵; Polish, A. R.¹⁴; Prouve, T.¹³; Pryke, C.¹¹; Reintsema, C. D.¹²; Romand, T.⁶; Salatino, M.⁸; Schillaci, A.⁶; Schmitt, B.⁵; Singari, B.¹¹; Sjoberg, K.⁵; Soliman, A.^{9, 6}; St Germaine, T.⁵; Steiger, A.⁶; Steinbach, B.⁶; Sudiwala, R.¹; Thompson, K. L.⁸; Tsai, C.⁵; Tucker, C.¹; Turner, A. D.⁹; Vergès, C.^{5, 16}; Vieregg, A. G.¹⁰; Wandui, A.⁶; Weber, A. C.⁹; Willmert, J.¹¹; Wu, W. L. K.^{3, 2}; Yang, H.⁸; Yu, C.^{8, 3}; Zeng, L.⁵; Zhang, C.⁶; Zhang, S.⁶; BICEP/Keck Collaboration

1. Cardiff University
2. Kavli Institute for Particle Astrophysics and Cosmology
3. SLAC National Accelerator Laboratory
4. University of British Columbia
5. Harvard-Smithsonian Center for Astrophysics
6. California Institute of Technology
7. University of Cincinnati
8. Stanford University
9. Jet Propulsion Lab
10. University of Chicago
11. University of Minnesota
12. National Institute of Standards and Technology
13. CEA Grenoble
14. Harvard University
15. University of Illinois Urbana-Champaign
16. Lawrence Berkeley National Laboratory

Abstract

We use a custom-made calibrator to measure individual detectors’ polarization angles of BICEP3, a small aperture telescope observing the cosmic microwave background (CMB) at 95 GHz from the South Pole. We describe our calibration strategy and the statistical and systematic uncertainties associated with the measurement. We reach an unprecedented precision for such measurement on a CMB experiment, with a repeatability for each detector pair of 0.02°. We show that the relative angles measured using this method are in excellent agreement with those extracted from CMB data. Because the absolute measurement is currently limited by a systematic uncertainty, we do not derive cosmic birefringence constraints from BICEP3 data in this work. Rather, we forecast the sensitivity of BICEP3 sky maps for such analysis. We investigate the relative contributions of instrument noise, lensing, and dust, as well as astrophysical and instrumental systematics. We also explore the constraining power of different angle estimators, depending on analysis choices. We establish that the BICEP3 2-year dataset (2017–2018) has an on-sky sensitivity to the cosmic birefringence angle of 𝜎𝛼 =0.07⁢8°, which could be improved to 𝜎𝛼 =0.05⁢5° by adding all of the existing BICEP3 data (through 2023). Furthermore, we emphasize the possibility of using the BICEP3 sky patch as a polarization calibration source for CMB experiments, which with the present data could reach a precision of 0.035°. Finally, in the context of inflation searches, we investigate the impact of detector-to-detector variations in polarization angles as they may bias the tensor-to-scalar ratio 𝑟. We show that while the effect is expected to remain subdominant to other sources of systematic uncertainty, it can be reliably calibrated using polarization angle measurements such as the ones we present in this paper.

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Acknowledgement

The BICEP/Keck projects have been made possible through a series of grants from the National Science Foundation most recently including Grants No. 2220444-2220448, No. 2216223, No. 1836010, and No. 1726917. The development of antenna-coupled detector technology was supported by the JPL Research and Technology Development Fund and by NASA Grants No. 06-ARPA206-0040, No. 10-SAT10-0017, No. 12-SAT12-0031, No. 14-SAT14-0009, and No. 16-SAT-16-0002. The development and testing of focal planes was supported by the Gordon and Betty Moore Foundation at Caltech. Readout electronics were supported by a Canada Foundation for Innovation grant to UBC. Support for quasioptical filtering was provided by UK STFC grant ST/N000706/1. The computations in this paper were run on the Odyssey/Cannon cluster supported by the FAS Science Division Research Computing Group at Harvard University. We thank the staff of the U.S. Antarctic Program and the South Pole Station who have enabled this research. We thank Hans Boenish and Sam Harrison, the BICEP3 winterovers for the years 2017 and 2018, as well as Karsten Look (2022 winterover) for his help in the 2022 calibration campaign. We also thank Marion Dierickx for her significant contributions during her tenure as the BICEP Operations Manager. We thank Susan Clark, Brandon Hensley, and Léo Vacher for useful discussions about dust models and dust contamination for birefringence searches. We thank Johannes Eskilt for his careful reading of our previous work, which has helped us address inaccuracies in our literature review and clear up inconsistencies in polarization orientation definition. Lastly, we thank Bill Holzapfel for his insight with investigating instrumental systematics.

Funding

The BICEP/Keck projects have been made possible through a series of grants from the National Science Foundation most recently including Grants No. 2220444-2220448, No. 2216223, No. 1836010, and No. 1726917. The development of antenna-coupled detector technology was supported by the JPL Research and Technology Development Fund and by NASA Grants No. 06-ARPA206-0040, No. 10-SAT10-0017, No. 12-SAT12-0031, No. 14-SAT14-0009, and No. 16-SAT-16-0002. The development and testing of focal planes was supported by the Gordon and Betty Moore Foundation at Caltech. Readout electronics were supported by a Canada Foundation for Innovation grant to UBC. Support for quasioptical filtering was provided by UK STFC grant ST/N000706/1.

Data Availability

The data that support the findings of this article are not publicly available. The data are available from the authors upon reasonable request.

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PhysRevD.111.063505.pdf

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