New constraints for CP-violating forces between nucleons in the range 10-4 cm - 1 cm

TL;DR

This paper establishes new experimental constraints on CP-violating nucleon forces within the 10^-4 to 1 cm range by analyzing ultracold neutron depolarization, significantly improving previous limits and discussing future search prospects.

Contribution

It provides the first constraints on CP-violating forces in the 10^-4 to 10^-1 cm range using ultracold neutron depolarization data, enhancing previous bounds by 4-5 orders of magnitude.

Findings

New upper limits on gS*gP*lam_PS^2 in specified range

Significant improvement over previous constraints

Discussion on future experimental sensitivity and theoretical implications

Abstract

The range of nucleon interaction 10-4 cm - 1 cm is interesting because it corresponds to the mass range of a intermediate particle inside so named "axion window" that is not closed yet by experiment. Depolarization of ultracold neutrons (UCN) during their storage in material traps can be caused by CP-violating pseudo-magnetic precession of the neutron spin in the vicinity of the unpolarized substance surface. Using the experimental limits for UCN depolarization new constraints were set for the product of the scalar, pseudo-scalar dimensionless constants gS*gP and the parameter lam_PS, determining the Yukawa-type of the nucleon interaction potential via new pseudo-scalar boson (axion-like particle) with a mass of m_PS: gS*gP*lam_PS^2 <= 2.96*10-21 [cm^2] for 10-3 cm < lam_PS < 1 cm; gS*gP*lam_PS^2 <= 3.9*10-22 [cm^2] for 10-4 cm < lam_PS < 10-3 cm. Improvement of the limit for gS*gP in the area of lam_PS from 0.1 cm to 1 cm accounts for 4-5 orders of magnitude in comparision with previous limit. The prospects of increasing in accuracy search for CP-violating pseudo-magnetic precession are considered. The estimations of the possible effects of pseudo-magnetic precession in the frame of the theoretical models with CP-violation are discussed.