Speaker
Description
Cosmic birefringence ($\text{CB}$)—the in-vacuum rotation of the linear polarization plane of photons—presents a compelling hint of parity-violating physics beyond the Standard Model. Recent analyses have brought this effect to the forefront of $\text{CMB}$ cosmology: Planck PR4 data yielded an estimate of $\beta = 0.3^\circ \pm 0.05^\circ \text{ (stat)} \pm 0.28^\circ \text{ (sys)}$, while the Atacama Cosmology Telescope ($\text{ACT}$) DR6 independently found $\beta = 0.2^\circ \pm 0.07^\circ$. Together, their combined significance stands at $4.6\sigma$, hovering just below the definitive discovery threshold.The primary bottleneck in confirming or ruling out this signal lies in the meticulous control of instrumental systematic effects, particularly polarization angle calibrations. In this talk, we discuss how to leverage the OpenHFI end-to-end $\text{CMB}$ maps, which benefit from the comprehensive systematic mitigation framework of the Cosmoglobe endeavor. By applying different $TB$ and $EB$ power spectra-based estimators to these freshly processed Planck HFI products, we demonstrate how to tightly constrain the cosmic birefringence angle. Finally, we show how this enhanced control over systematic contaminants impacts the total error budget and explore the potential of these maps to push the current detection significance past the $5\sigma$ threshold.