Novel Limits on Dark Photon Mixing from Radiation Safety

TL;DR

This paper introduces a new laboratory method using radiation safety monitoring at synchrotron facilities to detect dark photons, setting competitive limits on their properties with robust, realistic constraints.

Contribution

It proposes a novel approach leveraging existing radiation safety equipment at synchrotrons to search for dark photons, achieving strong bounds on their kinetic mixing.

Findings

Detected dark photons outside shielding using Geiger counters.

Set limits on dark photon kinetic mixing parameter down to ~5×10^{-6}.

Provided some of the strongest laboratory bounds on dark photons.

Abstract

I propose a novel laboratory search for dark photons based on radiation-safety monitoring at synchrotron radiation facilities, including NanoTerasu, SPring-8, KEK-PF, and ESRF. Dark photons can be produced parasitically in undulators or via photon-mirror interactions, and subsequently traverse optical systems and shielding. Taking into account quantum effects and the internal structure of undulators, mirrors, and detectors, I show that even a simple Geiger-M\"uller counter, routinely used for radiation-safety monitoring, can detect such dark photons outside the shielding and set competitive limits on the kinetic mixing parameter down to $\chi \lesssim 5\times 10^{-6}$ in the eV mass range, providing some of the strongest bounds among laboratory searches. Because radiation safety is strictly regulated, the resulting limits can be regarded as robust and realistic constraints.