New Constraints on Axion-Mediated Spin Interactions Using Magnetic Amplification.

Area of Science:

• Particle Physics
• Cosmology
• Quantum Mechanics

Background:

• Axions are hypothetical particles beyond the Standard Model, proposed as dark matter candidates and solutions to the strong CP problem.
• Detecting axions requires sensitive experimental methods capable of probing weak interactions.

Purpose of the Study:

• To search for axion-mediated interactions between two separated ^{129}Xe gas ensembles.
• To establish new constraints on neutron-neutron pseudoscalar couplings within the axion mass window.

Main Methods:

• Utilized spin-exchange interactions with Rubidium (Rb) vapor to monitor and polarize ^{129}Xe nuclear spins.
• Employed magnetic amplification through effective fields from Rb-Xe collisions, enhancing sensitivity by up to 145-fold.
• Applied template filtering to extract exotic interactions with a maximized signal-to-noise ratio.

Main Results:

• Constrained axion-mediated interactions to be less than 10^{-5} of normal magnetic interactions on a 60 mm length scale.
• Established new, significantly improved constraints on neutron-neutron pseudoscalar couplings, particularly within the 10 μeV–1 meV axion window.

Conclusions:

• The experiment sets unprecedented limits on axion properties, advancing searches for axion dark matter.
• The methodology shows promise for future searches for other axion-nucleon interactions and astrophysical axion phenomena.