doi:10.1103/PhysRevLett.134.151004engEgge, J.Leppla-Weber, D.Knirck, S.Ary dos Santos Garcia, B.Bergermann, D.Caldwell, A.Dabhi, V.Diaconu, C.Diehl, J.Dvali, G.Ekmedžic, M.Gallo, F.Garutti, E.Heyminck, S.Hubaut, F.Ivanov, A.Jochum, J.Karst, P.Kramer, M.Kreikemeyer-Lorenzo, D.Krieger, C.Lee, C.Lindner, A.Maldonado, J.¿P.¿A.Majorovits, B.Martens, S.Martini, A.Miyazaki, A.Öz, E.Pralavorio, P.Raffelt, G.Ringwald, A.Redondo, J.Roset, S.Salama, N.Schaffran, J.Schmidt, A.Steffen, F.Strandhagen, C.Usherov, I.Wang, H.Wieching, G.Cancelo, G.Di Federico, M.Hoshino, G.Stefanazzi, L.First Search for Dark Photon Dark Matter with a madmax PrototypeART-2025-143823We report the first result from a dark photon dark matter search in the mass range from 78.62 to 83.95  μeV/c2 with a dielectric haloscope prototype for (Magnetized Disc and Mirror Axion eXperiment). Putative dark photons would convert to detectable photons within a stack consisting of three sapphire disks and a mirror. The emitted power of this system is received by an antenna and successively digitized using a low-noise receiver. No significant signal attributable to dark photons has been observed above the expected background. Assuming unpolarized dark photon dark matter with a local density of ρχ=0.3  GeV cm3 we exclude a dark photon to photon mixing parameter χ>2.7×10−12 over the full mass range and χ>1.1×10−13 at a mass of 80.57  μeV/c2 with a 95% confidence level. This is the first physics result from a prototype and exceeds previous constraints on χ in this mass range by up to almost three orders of magnitude.2025http://zaguan.unizar.es/record/15362410.1103/PhysRevLett.134.151004http://zaguan.unizar.es/record/153624oai:zaguan.unizar.es:153624info:eu-repo/grantAgreement/ES/DGA-FSE/E21-17Rinfo:eu-repo/grantAgreement/ES/MICINN/PGC2022-126078NB-C21Physical Review Letters 134, 15 (2025), 151004 [7 pp.]byhttps://creativecommons.org/licenses/by/4.0/deed.esinfo:eu-repo/semantics/openAccess