# Constraints on exotic spin-velocity-dependent interactions

## TL;DR

This paper presents a new experimental search for exotic spin-velocity-dependent forces using a sensitive co-magnetometer, setting tighter limits on coupling constants than previous methods.

## Contribution

The study improves coupling constant limits for exotic spin-velocity-dependent forces using a novel experimental setup.

## Key findings

- The pseudomagnetic field from the exotic force is measured to be ≤7 aT.
- New coupling constant limits for neutron-nucleon and proton-nucleon interactions are established.
- Limits are more than one order of magnitude tighter than previous astronomical and cosmological constraints.

## Abstract

Experimental searches for exotic spin-dependent forces are attracting a lot of attention because they allow to test theoretical extensions to the standard model. Here, we report an experimental search for possible exotic spin-dependent force, specifically spin-and-velocity-dependent forces, by using a K-Rb-21Ne 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 this exotic force is measured to be ≤7 aT. This sets limits on coupling constants for the neutron-nucleon and proton-nucleon interactions in the range of ≥0.1 m (mediator boson mass ≤2 μeV). The coupling constant limits are established to be \documentclass[12pt]{minimal}
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\begin{document}$$|{g}_{V}^{n}|\,\le \,8.2\times 1{0}^{-11}$$\end{document}∣gVn∣≤8.2×10−11 and \documentclass[12pt]{minimal}
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\begin{document}$$|{g}_{V}^{p}|\,\le \,3.7\times 1{0}^{-10}$$\end{document}∣gVp∣≤3.7×10−10, 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.

Exotic spin-dependent force are among the possible extensions of the Standard Model that can be probed by precision measurements. Here, the authors use a spin-exchange-relaxation free (SERF) K-Rb-21Ne comagnetometer to improve limits on spin- and velocity dependent forces.