First Results from a Microwave Cavity Axion Search at 24  μeV.

Area of Science:

• Particle Physics
• Cosmology
• Astrophysics

Background:

• Dark matter axions are hypothetical particles proposed to solve the dark matter problem.
• Existing experimental searches have explored a limited range of axion masses and couplings.
• The standard quantum limit represents the theoretical minimum noise achievable in a measurement.

Purpose of the Study:

• To present the first results from a novel microwave cavity search for dark matter axions.
• To probe axion masses above 20 µeV, a region with limited prior investigation.
• To establish new exclusion limits on axion properties, specifically their two-photon coupling.

Main Methods:

• Utilizing a new microwave cavity experiment designed to detect axions.
• Employing a dilution refrigerator for ultra-low temperature operation.
• Incorporating a Josephson parametric amplifier to minimize noise.

Main Results:

• Exclusion of axion models with two-photon coupling g_{aγγ}≳2×10^{-14} GeV^{-1} in the mass range 23.55–24.0 µeV.
• Achieved unprecedented mass sensitivity, an order of magnitude higher than previous limits.
• Demonstrated experimental noise levels approaching the standard quantum limit.

Conclusions:

• The experiment sets new constraints on dark matter axion models.
• The technological advancements represent a significant step forward in axion detection sensitivity.
• Future iterations of this search hold promise for further exploring the dark matter axion parameter space.