Search

We report on the results from a search for dark matter axions with the HAYSTAC experiment using a microwave cavity detector at frequencies between 5.6 and 5.8 GHz. We exclude axion models with two photon coupling gaγγ≳2×10−14 GeV−1, a factor of 2.7 above the benchmark KSVZ model over the mass range 23.15

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 23.55m_{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.

We report detailed spectroscopic measurements of the X(0)[{sup 1}{sigma}{sup +}](v=0){yields}B(1)[{sup 3}{pi}](v=5) transition in PbO. Using a Stark-modulated laser absorption technique, we have measured the hyperfine constant of {sup 207}PbO in the B(1) state, as well as the B(1)(v=5) rotational constant, X-B isotope shifts, etc. The hyperfine constant of the B(1) state is of interest as a benchmark for calculations of PbO electronic structure related to experiments to search for the electric dipole moment of the electron.