Synchrotron-Like Radiation Beyond The Standard Model I: Hunting for new physics with the Sokolov-Ternov effect

TL;DR

This paper explores how new ultralight particles could influence electron and positron beam polarization times in storage rings, proposing a method to detect such particles through modifications in synchrotron radiation emission.

Contribution

It introduces a novel approach to search for ultralight particles by analyzing their effects on synchrotron-like radiation and polarization times in existing storage-ring experiments.

Findings

Set new limits on ultralight axial-vector particles coupled to electrons and positrons.

Calculated the impact of new particles on spin-flipping synchrotron radiation rates.

Demonstrated the potential of using polarization measurements to probe beyond Standard Model physics.

Abstract

Electron and positron beams in storage-rings self-polarize by emitting spin-flipping synchrotron radiation. If new ultralight particles couple to $e^\pm$, their emission in synchrotron-like radiation would modify the characteristic self-polarization time. We calculate the rate of spin-flipping synchrotron-like radiation in several simplified models, and find that the largest contribution is for an axial-vector. We use polarization time measurements from the Swiss-Light-Source, and SPEAR3 to set new strong limits on ultralight axial-vectors coupled to $e^\pm$.