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CMB-S4: forecasting constraints on primordial gravitational waves

Abstract:

CMB-S4—the next-generation ground-based cosmic microwave background (CMB) experiment—is set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2–3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r > 0.003 at greater than 5σ, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL.

Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.3847/1538-4357/ac1596

Authors


More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Physics
Sub department:
Astrophysics
Oxford college:
St Peter's College
Role:
Author
ORCID:
0000-0002-4598-9719
et al.


Publisher:
American Astronomical Society
Journal:
Astrophysical Journal More from this journal
Volume:
926
Issue:
54
Publication date:
2022-02-11
Acceptance date:
2021-07-08
DOI:
EISSN:
1538-4357
ISSN:
0004-637X


Keywords:
Pubs id:
1241508
Local pid:
pubs:1241508
Deposit date:
2023-01-04

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