Probing Primordial Gravitational Waves: Ali CMB Polarization Telescope

TL;DR

The Ali CMB Polarization Telescope project aims to detect primordial gravitational waves and test fundamental physics by building ground-based telescopes in Tibet, with expected significant improvements in measurement sensitivity over three years.

Contribution

This paper introduces the AliCPT project, a new ground-based CMB polarization experiment in China, with innovative telescope design and projected advancements in probing early Universe physics.

Findings

AliCPT will improve constraints on tensor-to-scalar ratio by an order of magnitude.

The project will enable precise measurements of CMB rotation angle and CPT symmetry.

AliCPT-1 will be the highest ground-based CMB observatory in the northern hemisphere.

Abstract

In this paper, we will give a general introduction to the project of Ali CMB Polarization Telescope (AliCPT), which is a Sino-US joint project led by the Institute of High Energy Physics (IHEP) and has involved many different institutes in China. It is the first ground-based Cosmic Microwave Background (CMB) polarization experiment in China and an integral part of China's Gravitational Waves Program. The main scientific goal of AliCPT project is to probe the primordial gravitational waves (PGWs) originated from the very early Universe. The AliCPT project includes two stages. The first stage referred to as AliCPT-1, is to build a telescope in the Ali region of Tibet with an altitude of 5,250 meters. Once completed, it will be the worldwide highest ground-based CMB observatory and open a new window for probing PGWs in northern hemisphere. AliCPT-1 telescope is designed to have about 7,000 TES detectors at 90GHz and 150GHz. The second stage is to have a more sensitive telescope (AliCPT-2) with the number of detectors more than 20,000. Our simulations show that AliCPT will improve the current constraint on the tensor-to-scalar ratio $r$ by one order of magnitude with 3 years' observation. Besides the PGWs, the AliCPT will also enable a precise measurement on the CMB rotation angle and provide a precise test on the CPT symmetry. We show 3 years' observation will improve the current limit by two order of magnitude.