Extended Axion Dark Matter Search Using the CAPP18T Haloscope

Area of Science:

• Particle Physics
• Cosmology
• Astrophysics

Background:

• Dark matter constitutes a significant portion of the universe's mass.
• The axion is a leading candidate particle for dark matter.
• Haloscope experiments are designed to detect axions by their conversion into photons within a resonant cavity.

Purpose of the Study:

• To conduct an extended search for axion dark matter using the CAPP18T haloscope.
• To establish new upper limits on the axion-photon-photon coupling constant.
• To demonstrate the capability of advanced technologies for high-mass dark matter axion searches.

Main Methods:

• Utilized the CAPP18T haloscope equipped with a high-temperature superconducting magnet and a Josephson parametric converter.
• Reconstructed the detector system after a magnet quench, optimizing impedance matching and cavity tuning.
• Scanned a frequency range of 4.8077 to 4.8181 GHz with a total system noise temperature of ~0.6 K.
• Maintained cavity-antenna coupling at β≃2 for enhanced scanning speed.

Main Results:

• No significant signature of axion dark matter was observed in the scanned frequency range.
• Established the best upper bound on axion-photon-photon coupling (g_{aγγ}) for axion masses of 19.883 to 19.926 μeV.
• Achieved bounds of ~0.7×|g_{aγγ}^{KSVZ}| or ~1.9×|g_{aγγ}^{DFSZ}| at a 90% confidence level.

Conclusions:

• The CAPP18T experiment successfully performed a reliable search for high-mass dark matter axions.
• The adopted innovative technologies demonstrate potential for future dark matter searches beyond benchmark models.
• The results contribute to constraining axion properties and the nature of dark matter.