Abstract :
Measurements of the CMB polarization anisotropies, subsequently to the temperature anisotropies, provide an additional probe into the cosmic inflation paradigm. For this reason, the CMB community is focusing on measuring the power of the parity-odd polarization component, the so-called B-mode polarization, on degree scales and larger that could be directly sourced by a primordial background of stochastic gravitational waves. However, the robustness of any cosmological analysis strongly depends on the knowledge of the instrument. Optical systematics contribute significantly to a CMB experiment’s estimated error budget, which makes beam calibration a priority. Improper modeling of the beam may result in biases both at the low multipole range of the angular CMB spectra, where the B-modes are expected to peak, as well as the higher multipole range, which is used to measure parameters such as the number of effective species and the helium fraction. For this reason, current- and next-generation CMB experiments launch extensive beam calibration campaigns employing both astrophysical and artificial sources. In this talk, I will present an overview of the key beam systematics relevant to CMB analysis and the most common calibration techniques employed by the community. The last part will be dedicated to the beam characterization analysis for the soon-to-be-deployed Simons Observatory (SO) Small Aperture Telescopes (SATs).
