167 research outputs found
Radio Sources Toward Galaxy Clusters at 30 GHz
Extra-galactic radio sources are a significant contaminant in cosmic
microwave background and Sunyaev-Zel'dovich effect experiments. Deep
interferometric observations with the BIMA and OVRO arrays are used to
characterize the spatial, spectral, and flux distributions of radio sources
toward massive galaxy clusters at 28.5 GHz. We compute counts of mJy source
fluxes from 89 fields centered on known massive galaxy clusters and 8
non-cluster fields. We find that source counts in the inner regions of the
cluster fields (within 0.5 arcmin of the cluster center) are a factor of 8.9
(+4.3,-2.8) times higher than counts in the outer regions of the cluster fields
(radius greater than 0.5 arcmin). Counts in the outer regions of the cluster
fields are in turn a factor of 3.3 (+4.1,-1.8) greater than those in the
non-cluster fields. Counts in the non-cluster fields are consistent with
extrapolations from the results of other surveys. We compute spectral indices
of mJy sources in cluster fields between 1.4 and 28.5 GHz and find a mean
spectral index of alpha = 0.66 with an rms dispersion of 0.36, where flux is
proportional to frequency raised to negative alpha. The distribution is skewed,
with a median spectral index of 0.72 and 25th and 75th percentiles of 0.51 and
0.92, respectively. This is steeper than the spectral indices of stronger field
sources measured by other surveys.Comment: 32 pages, 6 figures, accepted to A
ADMX-Orpheus First Search for 70 eV Dark Photon Dark Matter: Detailed Design, Operations, and Analysis
Dark matter makes up 85% of the matter in the universe and 27% of its energy
density, but we don't know what comprises dark matter. It is possible that dark
matter may be composed of either axions or dark photons, both of which can be
detected using an ultra-sensitive microwave cavity known as a haloscope. The
haloscope employed by ADMX consists of a cylindrical cavity operating at the
TM mode and is sensitive to the QCD axion with masses of few eV.
However, this haloscope design becomes challenging to implement for higher
masses. This is because higher masses require smaller-diameter cavities,
consequently reducing the detection volume which diminishes the detected signal
power. ADMX-Orpheus mitigates this issue by operating a tunable,
dielectrically-loaded cavity at a higher-order mode, allowing the detection
volume to remain large. This paper describes the design, operation, analysis,
and results of the inaugural ADMX-Orpheus dark photon search between 65.5
eV (15.8 GHz) and 69.3 eV (16.8 GHz), as well as future directions
for axion searches and for exploring more parameter space.Comment: 21 pages, 29 figures. To be submitted to Physical Review D. arXiv
admin note: substantial text overlap with arXiv:2112.0454
Search for 70 \mu eV Dark Photon Dark Matter with a Dielectrically-Loaded Multi-Wavelength Microwave Cavity
Microwave cavities have been deployed to search for bosonic dark matter
candidates with masses of a few eV. However, the sensitivity of these
cavity detectors is limited by their volume, and the traditionally-employed
half-wavelength cavities suffer from a significant volume reduction at higher
masses. ADMX-Orpheus mitigates this issue by operating a tunable,
dielectrically-loaded cavity at a higher-order mode, which allows the detection
volume to remain large. The ADMX-Orpheus inaugural run excludes dark photon
dark matter with kinetic mixing angle between 65.5 eV
(15.8 GHz) and 69.3 eV (16.8GHz), marking the highest-frequency tunable
microwave cavity dark matter search to date.Comment: 7 pages, 5 figure, to be submitted to PR
Results from the Project 8 phase-1 cyclotron radiation emission spectroscopy detector
The Project 8 collaboration seeks to measure the absolute neutrino mass scale
by means of precision spectroscopy of the beta decay of tritium. Our technique,
cyclotron radiation emission spectroscopy, measures the frequency of the
radiation emitted by electrons produced by decays in an ambient magnetic field.
Because the cyclotron frequency is inversely proportional to the electron's
Lorentz factor, this is also a measurement of the electron's energy. In order
to demonstrate the viability of this technique, we have assembled and
successfully operated a prototype system, which uses a rectangular waveguide to
collect the cyclotron radiation from internal conversion electrons emitted from
a gaseous Kr source. Here we present the main design aspects of the
first phase prototype, which was operated during parts of 2014 and 2015. We
will also discuss the procedures used to analyze these data, along with the
features which have been observed and the performance achieved to date.Comment: 3 pages; 2 figures; Proceedings of Neutrino 2016, XXVII International
Conference on Neutrino Physics and Astrophysics, 4-9 July 2016, London, U
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