We report the refined dark-photon exclusion bound from Dark SRF's pathfinder run. Our new result is driven by improved theoretical modeling of frequency instability in high-quality resonant experiments. Our analysis leads to a constraint that is an order of magnitude stronger than previously reported (corresponding to a signal-to-noise ratio that is four orders of magnitude larger). This result represents the world-leading constraint on non-dark-matter dark photons over a wide range of masses below 6μeV and translates to the best laboratory-based limit on the photon mass mγ<2.9×10−48g.
@article{arxiv.2510.02427,
title = {Improved Dark Photon Sensitivity from the Dark SRF Experiment},
author = {Saarik Kalia and Zhen Liu and Bianca Giaccone and Oleksandr Melnychuk and Roman Pilipenko and Asher Berlin and Anson Hook and Sergey Belomestnykh and Crispin Contreras-Martinez and Daniil Frolov and Timergali Khabiboulline and Yuriy Pischalnikov and Sam Posen and Oleg Pronitchev and Vyacheslav Yakovlev and Anna Grassellino and Roni Harnik and Alexander Romanenko},
journal= {arXiv preprint arXiv:2510.02427},
year = {2026}
}