Proposal to use accelerated electrons to probe the axion-electron coupling

Abstract

The axion is a hypothetical particle associated with a possible solution to the strong CP problem and is a leading candidate for dark matter. In this paper we investigate the emission of axions by accelerated electrons. We find the emission probability and energy within the WKB approximation for an electron accelerated by an electromagnetic field. As an application, we estimate the number of axions produced by electrons accelerated using two counter-propagating high-intensity lasers and discuss how they would be converted to photons to be detected. We find that, under realistic experimental conditions, competitive model-independent bounds on the coupling between the axion and the electron could be achieved in such an experiment.

Figures (4)

• Figure 1: Diagram of the experimental proposal. We assume that there are enough detectors to cover a large solid angle.
• Figure 2: Bounds of laboratory-based experiments. The red and black curves correspond to the bounds found in PhysRevLett.124.211804, and Constraining_exotic_spin respectively. The orange band is the DFSZ prediction Zhitnitsky:1980tqDine:1981rtPhysRevD.33.897. For the next-generation laser, we assumed one year of measurement instead of one week.
• Figure 3: Number of axions produced in one cycle (estimated by dividing the total energy by the typical axion energy) by one on-node electron (blue-dashed line) and by one off-node electron (red-solid line) with initial condition $\omega_0 x(0) = \pi/3$. The number was averaged over ten cycles.
• Figure 4: The Feynman diagrams for the axion emission: The solid line represents the electron and the dashed line represents the axion. The dot represents the interaction of the electron with the external potential.