Search for Dark Matter Axions with CAST-CAPP.

Area of Science:

• Particle Physics
• Cosmology
• Astrophysics

Background:

• Axions are hypothetical particles proposed as a dark matter candidate.
• The CAST experiment at CERN utilizes a dipole magnet to search for axions.
• The haloscope detection principle relies on axion-to-photon conversion in a magnetic field.

Purpose of the Study:

• To search for axions within the 19.74–22.47 μeV mass range.
• To constrain the axion-photon coupling constant (g_aγγ).
• To test the efficacy of phase-matching techniques for future axion haloscope upgrades.

Main Methods:

• Utilized the CAST-CAPP axion haloscope, an array of four phase-matched rectangular cavities.
• Operated within the CERN CAST dipole magnet from 2019 to 2021, accumulating 4124 hours of data.
• Employed fast frequency tuning mechanisms (10 MHz/min) across the 4.774–5.434 GHz range.

Main Results:

• Excluded axion-photon couplings down to g_aγγ = 8 × 10^-14 GeV^-1 at the 90% confidence level for virialized galactic axions.
• The data covers the axion mass range of 19.74–22.47 μeV.
• Demonstrated the feasibility of the phase-matching technique for enhanced sensitivity.

Conclusions:

• The CAST-CAPP experiment has set new limits on axion properties.
• The implemented phase-matching technique shows promise for future, more sensitive dark matter searches.
• Further upgrades incorporating this technique could significantly improve dark matter detection.