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Improved Dark Photon Sensitivity from a Superconducting-Radio-Frequency-Cavity Experiment

Saarik Kalia ^1,*, Zhen Liu ^1,†, Bianca Giaccone ², Oleksandr Melnychuk ², Roman Pilipenko², Asher Berlin ³, Anson Hook ⁴, Sergey Belomestnykh ⁵, Crispin Contreras-Martinez⁵ et al.

Daniil Frolov^2,‡, Timergali Khabiboulline ⁵, Yuriy Pischalnikov ⁵, Sam Posen ⁵, Oleg Pronitchev ², Vyacheslav Yakovlev ², Anna Grassellino^2,§, Roni Harnik^3,∥, and Alexander Romanenko ^5,¶

¹School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
²Superconducting Quantum Materials and Systems Center (SQMS) Division, Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA
³Theoretical Physics Division, Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA
⁴Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
⁵Applied Physics and Superconducting Technology Directorate, Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA

^*Contact author: kalias@umn.edu
^†Contact author: zliuphys@umn.edu
^‡Present address: IBM Research, Yorktown Heights, New York 10598, USA.
^§Contact author: annag@fnal.gov
^∥Contact author: roni@fnal.gov
^¶Contact author: aroman@fnal.gov

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Phys. Rev. Lett. 136, 111802 – Published 18 March, 2026

DOI: https://doi.org/10.1103/p7r3-c15d

Abstract

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 4 orders of magnitude larger). This result represents the world-leading constraint on non-dark-matter dark photons over a wide range of masses below $6 μ eV$ and translates to the best laboratory-based limit on the photon mass $m_{γ} < 2.9 \times 10^{- 48} g$ .

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Github, https://github.com/ZhenLiuPhys/JitterModel/blob/main/Research/NewDarkSRFlimits.

Phys. Rev. Lett. 136, 111802– Published 18 March, 2026

Vol. 136, Iss. 11 — 20 March 2026

Received 20 October 2025
Accepted 24 February 2026

DOI: https://doi.org/10.1103/p7r3-c15d

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Improved Dark Photon Sensitivity from a Superconducting-Radio-Frequency-Cavity Experiment

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Modeling frequency instability in high-quality resonant experiments

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