title: First Results from a Microwave Cavity Axion Search at 24  μeV.
abstract: We report on the first results from a new microwave cavity search for dark matter axions with masses above 20  μeV. We exclude axion models with two-photon coupling g_{aγγ}≳2×10^{-14}  GeV^{-1} over the range 23.55<m_{a}<24.0  μeV. These results represent two important achievements. First, we have reached cosmologically relevant sensitivity an order of magnitude higher in mass than any existing limits. Second, by incorporating a dilution refrigerator and Josephson parametric amplifier, we have demonstrated total noise approaching the standard quantum limit for the first time in an axion search.
authors.affiliation: Department of Physics, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: B M
authors.initials: BM
authors.lastname: Brubaker
authors.affiliation: Department of Physics, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: L
authors.initials: L
authors.lastname: Zhong
authors.affiliation: Department of Physics, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Y V
authors.initials: YV
authors.lastname: Gurevich
authors.affiliation: Department of Physics, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: S B
authors.initials: SB
authors.lastname: Cahn
authors.affiliation: Department of Physics, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Lamoreaux
authors.affiliation: Department of Nuclear Engineering, University of California Berkeley, Berkeley, California 94720, USA.
authors.forename: M
authors.initials: M
authors.lastname: Simanovskaia
authors.affiliation: Department of Nuclear Engineering, University of California Berkeley, Berkeley, California 94720, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Root
authors.affiliation: Department of Nuclear Engineering, University of California Berkeley, Berkeley, California 94720, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Lewis
authors.affiliation: Department of Nuclear Engineering, University of California Berkeley, Berkeley, California 94720, USA.
authors.forename: S
authors.initials: S
authors.lastname: Al Kenany
authors.affiliation: Department of Nuclear Engineering, University of California Berkeley, Berkeley, California 94720, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Backes
authors.affiliation: Department of Nuclear Engineering, University of California Berkeley, Berkeley, California 94720, USA.
authors.forename: I
authors.initials: I
authors.lastname: Urdinaran
authors.affiliation: Department of Nuclear Engineering, University of California Berkeley, Berkeley, California 94720, USA.
authors.forename: N M
authors.initials: NM
authors.lastname: Rapidis
authors.affiliation: Department of Nuclear Engineering, University of California Berkeley, Berkeley, California 94720, USA.
authors.forename: T M
authors.initials: TM
authors.lastname: Shokair
authors.affiliation: Department of Nuclear Engineering, University of California Berkeley, Berkeley, California 94720, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: van Bibber
authors.affiliation: JILA and the Department of Physics, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Palken
authors.affiliation: JILA and the Department of Physics, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309, USA.
authors.forename: M
authors.initials: M
authors.lastname: Malnou
authors.affiliation: JILA and the Department of Physics, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309, USA.
authors.forename: W F
authors.initials: WF
authors.lastname: Kindel
authors.affiliation: JILA and the Department of Physics, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Anil
authors.affiliation: JILA and the Department of Physics, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309, USA.
authors.forename: K W
authors.initials: KW
authors.lastname: Lehnert
authors.affiliation: Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA.
authors.forename: G
authors.initials: G
authors.lastname: Carosi