Performance forecasts for the primordial gravitational wave detection pipelines for AliCPT-1

AliCPT is the first Chinese cosmic microwave background (CMB) experiment which will make the most precise measurements of the CMB polarization in the northern hemisphere. The key science goal for AliCPT is the detection of primordial gravitational waves (PGWs). It is well known that an epoch of cosmic inflation, in the very early universe, can produce PGWs, which leave an imprint on the CMB in form of odd parity B-mode polar-ization. In this work, we study the performance of the component separation and parameter estimation pipelines in context of constraining the value of the tensor-to-scalar ratio. Based on the simulated data for one observation season, we compare five different pipelines with dif-ferent working principles. Three pipelines perform component separation at map or spectra level before estimating r from the cleaned spectra, while the other two pipelines performs a global fit for both foreground parameters and r. We also test different methods to account for the effects of time stream filtering systematics. This work shows that our pipelines provide consistent and robust constraints on the tensor-to-scalar ratio and a consistent sensitivity sigma(r) similar to 0.02. This showcases the potential of precise B-mode polarization measurement with AliCPT-1. AliCPT will provide a powerful opportunity to detect PGWs, which is comple-mentary with various ground-based CMB experiments in the southern hemisphere.

Automated summary

AliCPT is the first Chinese cosmic microwave background (CMB) experiment aiming to make the most precise measurements of CMB polarization in the northern hemisphere. Its key science goal is the detection of primordial gravitational waves (PGWs). Through the study and comparison of simulated data, it is found that AliCPT provides consistent and robust constraints on the tensor-to-scalar ratio, showcasing the potential of precise B-mode polarization measurement. It also complements various ground-based CMB experiments in the southern hemisphere.