First Results from the Taiwan Axion Search Experiment with a Haloscope at 19.6  μeV

Area of Science:

• Physics
• Particle Physics
• Cosmology

Background:

• Axions are hypothetical elementary particles proposed as a solution to the strong CP problem in quantum chromodynamics.
• The axion-two-photon coupling (g_aγγ) is a key parameter for detecting axions with resonant cavities.

Purpose of the Study:

• To search for axions in the mass range of approximately 19.4-19.8 μeV using a haloscope detector.
• To place experimental constraints on the axion-two-photon coupling parameter (g_aγγ).

Main Methods:

• Utilized the Taiwan Axion Search Experiment with a Haloscope (TASH).
• Employed a resonant microwave cavity to detect axion-induced photons.
• Operated the experiment at frequencies between 4.70750 and 4.79815 GHz.

Main Results:

• No axion signals with a significance greater than 3.355 were detected.
• Excluded axion models with |g_aγγ|≳8.1×10⁻¹⁴ GeV⁻¹ in the mass range 19.4687–19.8436 μeV.
• Achieved unprecedented sensitivity for haloscope experiments in the 19.4687–19.7639 μeV mass region, surpassing non-haloscope limits by three orders of magnitude.

Conclusions:

• The TASH experiment provides the first haloscope-based constraints on g_aγγ in this specific mass range.
• The results significantly improve upon existing experimental limits for axion detection.
• Further searches with improved sensitivity are warranted to explore the axion parameter space.