Dark Photons from Nuclear Transitions

TL;DR

This paper explores how nuclear transition experiments, especially with $^8$Be, can detect dark photons in the MeV mass range, offering a competitive and cost-effective method to probe new physics beyond collider experiments.

Contribution

It demonstrates that nuclear transition experiments can effectively search for dark photons in unexplored parameter space, complementing collider and fixed target experiments.

Findings

Nuclear transitions can detect dark photons with masses 1-18 MeV.

Experiments can probe kinetic mixing parameters $ ext{varepsilon}^2 extgreater 10^{-7}$.

Potential for rapid, low-cost searches in unexplored regions.

Abstract

Light new particles can be emitted in decays of excited nuclear states. Experiments analyzing such transitions and incorporating high-resolution detectors can be sensitive to new MeV-scale physics at a level competitive with upcoming collider and other fixed target experiments, provided sufficient luminosity. We demonstrate this in the case of the $^8\textrm{Be}$ system, showing that searches targeting the reported anomaly in $^8\textrm{Be}$ nuclear transitions can also be sensitive to currently unexplored regions of the canonical dark photon parameter space with 1 MeV $\lesssim m_{A^{\prime}} \lesssim 18$ MeV and $\varepsilon^2 \gtrsim10^{-7}$. These experiments could be performed on a short timescale, at low cost, and directly probe both the hadronic and leptonic couplings of light hidden particles.