A pair polarimeter for multi-GeV $\gamma$-rays

TL;DR

This paper introduces a novel, compact pair polarimeter design that combines active pixel sensors with low-density converters, achieving higher efficiency and analyzing power for multi-GeV gamma-ray polarization measurements, enabling new physics insights.

Contribution

The paper presents a new concept of a pair polarimeter using monolithic active pixel sensors and low-density converters, improving efficiency and analyzing power for high-energy gamma-ray polarization detection.

Findings

Achieves ~7% efficiency in polarization measurement.

Analyzing power ranges from 0.2 to 0.5.

Potential applications in multi-messenger physics and fundamental tests.

Abstract

Accessing the polarization of photon allows to understand the mechanisms behind its emission or scattering, revealing much about a peculiar environment or a probed object. For energy above $\sim$10~MeV, the pair production dominates the photon-matter interaction and the photon polarization is accessible via the azimuthal angle of the conversion. Unfortunately pair polarimeters have a low figure-of-merit for multi-GeV photons and are mostly used for beam characterization. In this paper, we report a new concept of a compact pair polarimeter associating monolithic active pixel sensors to low-density extended solid converters to reach simultaneously a high efficiency of $\sim$7\% and intrinsic analyzing power ranging from 0.2 to 0.5. This new concept will add a new obersvable to the multi-messenger physics, isolate the intrinsic strong force in nucleons and possibly reveal violations of Lorentz invariance.