Enhanced signature of vacuum birefringence in a plasma wakefield

TL;DR

This paper proposes a novel laser-plasma method to enhance the detection of vacuum birefringence, leveraging plasma wakefields to achieve larger interaction lengths and stronger fields, making experimental observation more feasible.

Contribution

The authors introduce a plasma wakefield-based approach that combines large interaction lengths and strong fields to improve vacuum birefringence detection, overcoming previous limitations.

Findings

VB signal can reach about 10^-5 for tens of MeV photons

VB signal can reach about 10^-3 to 10^-2 for GeV photons

Method effectively mitigates plasma electron noise

Abstract

Vacuum birefringence (VB) is a basic phenomenon predicted in quantum electrodynamics (QED). However, due to the smallness of the signal, conventional magnet-based and extremely intense laser-driven detection methods are still very challenging. This is because in the first case the interaction length is large but the field is limited, and vice versa in the second case. We put forward a method to generate and detect VB in a plasma bubble wakefield, which combines both advantages, providing large fields along large interaction lengths. A polarized $\gamma$-photon beam is considered to probe the wakefield along a propagation distance of millimeters to centimeters in the plasma bubble. We find via plasma particle-in-cell simulations that the VB signal in terms of Stokes parameters can reach about $ 10^{-5}$ ($10^{-3}$-$10^{-2}$) for tens of MeV (GeV) probe photons with moderately intense lasers ($10^{20}$-$10^{21}~\mathrm{W/cm^2}$). The main source of noise from plasma electrons is mitigated, in particular, by a choice of $\gamma$-photon polarization and by proper modulation of the plasma density. The proposed method represents an attractive alternative for the experimental observation of VB via laser-plasma interaction.