Fermion pair radiation from accelerating classical systems

TL;DR

This paper generalizes the Larmor formula to describe fermion pair radiation from accelerating classical systems, applying it to pulsar binaries to set bounds on new physics involving light mediators.

Contribution

It introduces a novel formula for fermion pair radiation from classical sources and explores its implications for astrophysical systems and beyond-standard-model physics.

Findings

Derived the fermion pair radiation formula for classical sources.

Applied the formula to pulsar binaries to constrain new physics.

Set bounds on mediator parameters using binary decay data.

Abstract

Accelerating classical systems that couple to a fermion-antifermion pair at the microscopic level can radiate pairs of fermions and lose energy in the process. In this work, we derive the generalization of the Larmor formula for fermion pair radiation. We focus on the case of a point-like classical source in an elliptical orbit that emits fermions through vector and scalar mediators. Ultra-light fermion emission from such systems becomes relevant when the mass of the mediator is larger than the frequency of the periodic motion. This enables us to probe regions of the parameter space that are inaccessible in on-shell bosonic radiation. We apply our results to pulsar binaries with mediators that couple to muons and neutrinos. Using current data on binary period decays, we extract bounds on the parameters of such models.