New limit on Lorentz- and CPT-violating neutron spin interactions

Area of Science:

• Fundamental physics
• Particle physics
• Cosmology

Background:

• Lorentz and CPT symmetry violations are theoretical possibilities in physics.
• Experimental searches for such violations are crucial for testing fundamental symmetries.
• Neutron spin interactions offer a sensitive probe for detecting new physics.

Purpose of the Study:

• To search for neutron spin coupling to a Lorentz- and CPT-violating background field.
• To establish new experimental limits on the strength of such hypothetical background fields.
• To enhance the sensitivity and precision of spin anisotropy measurements.

Main Methods:

• Utilized a magnetometer with overlapping ensembles of potassium (K) and helium-3 (³He) atoms.
• Mounted the comagnetometer on a rotary platform for frequent orientation reversal.
• Measured sidereal oscillations in the magnetometer signal to detect extra-solar field couplings.

Main Results:

• Determined the equatorial components of the background field interacting with the neutron spin.
• Established upper limits for these components: b˜Xn=(0.1 ± 1.6) × 10⁻³³ GeV and b˜Yn=(2.5 ± 1.6) × 10⁻³³ GeV.
• Improved the previous experimental limit by a factor of 30.

Conclusions:

• The experiment set stringent new limits on neutron spin coupling to exotic background fields.
• This measurement represents the highest energy resolution achieved in any spin anisotropy experiment to date.
• The findings contribute to the ongoing search for physics beyond the Standard Model and violations of fundamental symmetries.