28461 2507.16888 10.1007/JHEP03(2026)155 155 155 Electroweak precision constraints on dark photon models with generalized mixing Regular Article - Theoretical Physics 1 27 2026 3 16 2025 8 28 2026 1 24 2026 1 26 2026 3 16 2026 3 16 National Science Foundation PHY-2309456 United States-Israel Binational Science Foundation 2016153 The Author(s) 2026 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 2026 2026 3 3 Enrico Bertuzzo enrico.bertuzzo@unimore.it Csaba Csaki csaki@cornell.edu Fernanda Huller fh264@cornell.edu https://ror.org/02d4c4y02 grid.7548.e 0000 0001 2169 7570 Dipartimento di Scienze Fisiche, Informatiche e Matematiche Università degli Studi di Modena e Reggio Emilia via G. Campi 213/A 41125 Modena Italy https://ror.org/04j0x0h93 grid.470193.8 0000 0004 8343 7610 INFN sezione di Bologna via Irnerio 46 40126 Bologna Italy https://ror.org/05bnh6r87 grid.5386.8 0000 0004 1936 877X Laboratory for Elementary Particle Physics Cornell University Ithaca NY 14853 USA Abstract We present a global fit to electroweak precision observables (EWPOs) in dark photon (DP) models containing both kinetic and mass mixing between the DP and the neutral gauge bosons of the Standard Model (SM). Such more general mixing can be the result of an extended scalar sector, which we specify in this paper. We calculate the tree-level contributions to EWPOs due to the mixing with the DP, as well as the leading loop corrections to the oblique parameters due to the extended Higgs sector. In the scalar sector, we find that ample regions of parameter space are still unconstrained by data. In the gauge sector, the excluded region depends strongly on the vacuum expectation values of the scalar fields: for moderate ratios, DP masses in the (40 GeV, 1 TeV) range are excluded; for larger ratios, the limits become indistinguishable from those for standard DPs. Keywords Electroweak Precision Physics New Gauge Interactions ArXiv ePrint: 2507.16888