26127 2412.17777 10.1007/JHEP05(2025)052 52 52 Dark gauge-mediated supersymmetry breaking with a massless dark photon Regular Article - Theoretical Physics 1 45 2025 5 7 2024 12 27 2025 3 24 2025 3 27 2025 5 7 The Author(s) 2025 Open Access. This article is distributed under the terms of the Creative Commons Attribution License ( CC-BY 4.0 ), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited. 13130 2025 2025 5 5 Brian Batell batell@pitt.edu Yechan Kim cj7801@kaist.ac.kr Hye-Sung Lee hyesung.lee@kaist.ac.kr Jiheon Lee anffl0101@kaist.ac.kr https://ror.org/01an3r305 grid.21925.3d 0000 0004 1936 9000 Pittsburgh Particle Physics, Astrophysics, and Cosmology Center, Department of Physics and Astronomy University of Pittsburgh Pittsburgh PA 15217 USA https://ror.org/05apxxy63 grid.37172.30 0000 0001 2292 0500 Department of Physics Korea Advanced Institute of Science and Technology Daejeon 34141 Korea https://ror.org/01ggx4157 grid.9132.9 0000 0001 2156 142X Theoretical Physics Department CERN 1 Esplanade des Particules CH-1211 Geneva 23 Switzerland Abstract We study dark gauge-mediated supersymmetry breaking (dark GMSB) in a theory with a new unbroken U(1) D local symmetry and massless dark photon. Messenger fields charged under both Standard Model and dark gauge symmetries produce new soft supersymmetry-breaking terms due to gauge kinetic mixing between U(1) Y hypercharge and U(1) D . We show that large kinetic mixing induces significant distortions to the superpartner spectra relative to conventional GMSB. Notably, shifts in the Higgs soft masses impact the conditions for electroweak symmetry breaking, lowering the μ parameter and yielding a relatively light Higgsino that may be accessible at the LHC. Furthermore, for very simple messenger representations, a very light bino-dark photino mixed state is present in the spectrum, which may be probed through exotic Higgs boson decays at future Higgs factories. We also examine the cosmological and phenomenological consequences of the messengers, the lightest of which is absolutely stable and carries fractional electric charge. Keywords Supersymmetry New Gauge Interactions New Light Particles ArXiv ePrint: 2412.17777