Improved constraints on an axion-mediated force.

Area of Science:

• Particle Physics
• Astrophysics
• Fundamental Symmetries

Background:

• Low mass pseudoscalars, like the axion, are theorized to mediate forces violating parity and time-reversal symmetries.
• Searching for such exotic forces probes beyond the Standard Model of particle physics.
• These forces could have implications for cosmology and astrophysics.

Purpose of the Study:

• To search for macroscopic parity and time-reversal symmetry-violating forces mediated by low mass pseudoscalars.
• To improve existing laboratory constraints on the properties of axion-like particles.
• To explore a broad range of particle masses relevant to astrophysical phenomena.

Main Methods:

• Utilized a novel, magnetically unshielded torsion pendulum to detect subtle forces.
• Employed polarized electrons and unpolarized atoms as the source and target for the potential force.
• Performed high-precision measurements to enhance sensitivity to weak interactions.

Main Results:

• Improved laboratory bounds on pseudoscalar-mediated forces by over 10 orders of magnitude for masses above 1 meV.
• Constrained these forces across a wide range of astrophysically interesting masses, from 10 μeV to 10 meV.
• Established new, stringent limits on axion-like particle interactions with ordinary matter.

Conclusions:

• The experiment provides the most stringent laboratory constraints to date on certain axion-like particle models.
• The results significantly narrow the parameter space for pseudoscalar particles mediating macroscopic forces.
• This work opens new avenues for searching for new physics beyond the Standard Model using precision measurements.