Forecasts of constraining isotropic cosmic birefringence on AliCPT-1

Abstract

Cosmic birefringence (CB) is a promising probe of parity-violating physics beyond the Standard Model, characterized by the rotation of the linear polarization plane of cosmic microwave background (CMB) photons. This effect, quantified by the birefringence angle $\beta$, generates non-zero $EB$ and $TB$ correlations that are otherwise absent in standard cosmology. However, instrumental miscalibration angles $\alpha$ can mimic this signal, necessitating a joint estimation approach. In this work, we forecast the sensitivity of the AliCPT experiment, combined with Planck HFI data, on constraining the isotropic CB angle using a semi-analytical maximum-likelihood method. We simulate observations under various foreground complexities, rotation angles, and scanning strategies, and demonstrate that AliCPT can achieve an uncertainty of $\sigma(\beta)=0.09^\circ$ with one-year data, which will improve to $0.026^\circ$ after four years' observations. We also find that neglecting or mismodeling the foreground $EB$ correlation will introduce significant biases, which can be alleviated under a clean but small sky patch.