New constraints on short-range forces coupling mass to intrinsic spin

Area of Science:

• Experimental physics
• Fundamental forces
• Spin physics

Background:

• The Standard Model of particle physics does not predict new forces coupling to mass and intrinsic spin.
• Previous experiments have searched for such interactions, but sensitivity remains limited at certain ranges.

Purpose of the Study:

• To search for a novel force that couples mass to intrinsic spin.
• To establish new experimental limits on the dimensionless coupling constant of such an interaction.
• To enhance sensitivity in the search for spin-dependent forces.

Main Methods:

• Utilized a novel spherical superconducting torsion balance.
• Employed a unique spin-source geometry for increased sensitivity.
• Conducted experiments to probe interactions in the range of 100 micrometers to 5 millimeters.

Main Results:

• Established new upper limits on the dimensionless coupling constant g_{p};{e}g_{s}.
• Achieved a limit of g_{p};{e}g_{s}<(-1.9 +/- (1.3)_{stat} +/- (1.5)_{syst})x10^{-26} for lambda > 10 mm at 1 sigma confidence.
• Set a relaxed limit of g_{p};{e}g_{s}<1.5x10^{-24} at a range of 1 mm.

Conclusions:

• The experiment provides stringent new constraints on hypothetical spin-coupled forces.
• The results narrow the parameter space for new physics beyond the Standard Model.
• The developed apparatus demonstrates unprecedented sensitivity for probing spin-dependent interactions.