New Constraints on Exotic Spin-Velocity-Dependent Interactions

TL;DR

This paper reports a highly sensitive experimental search for spin-velocity dependent fifth forces using a co-magnetometer and tungsten ring, setting new stringent limits on neutron and proton coupling constants that surpass previous astrophysical constraints.

Contribution

The study introduces a novel experimental approach with a co-magnetometer and tungsten ring to significantly tighten limits on spin-velocity dependent fifth forces beyond prior astrophysical bounds.

Findings

Measured pseudomagnetic field from fifth force <7 aT.

Set new upper limits on neutron-nucleon coupling |g_V^n|<6.6×10^{-11}.

Set new upper limits on proton-nucleon coupling |g_V^p|<3.0×10^{-10}.

Abstract

Experimental searches for new, "fifth" forces are attracting a lot of attention because they allow to test theoretical extensions to the standard model. Here, we report a new experimental search for possible fifth forces, specifically spin-and-velocity dependent forces, by using a K-Rb-$^{21}$Ne co-magnetometer and a tungsten ring featuring a high nucleon density. Taking advantage of the high sensitivity of the co-magnetometer, the pseudomagnetic field from the fifth force is measured to be $<7$\,aT. This sets new limits on coupling constants for the neutron-nucleon and proton-nucleon interactions in the range of $\ge 0.1$ m. The coupling constant limits are established to be $|g_V^n|<6.6\times 10^{-11}$ and $|g_V^p|<3.0\times 10^{-10}$, which are more than one order of magnitude tighter than astronomical and cosmological limits on the coupling between the new gauge boson such as Z$'$ and standard model particles.