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

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 $e^{\pm }$.

Comments: 18 pages, 1 figure