Probe Spin-Velocity Dependent New Interactions by Spin Relaxation Times of Polarized $^{3}He$ Gas

TL;DR

This study uses polarized helium-3 spin relaxation times to set new experimental limits on hypothetical velocity-dependent spin interactions and torsion fields, improving constraints over a wide range of interaction ranges.

Contribution

The paper introduces a novel method to constrain velocity-dependent spin interactions using existing helium-3 relaxation data, providing the first limits on earth-induced torsion fields.

Findings

Set new bounds on vector-axial-vector interactions for ranges 1m to 10^8m.

Established the most stringent limits on g_V g_A from micrometer to 10^8 meters.

Provided the first experimental upper limit on torsion fields induced by the earth.

Abstract

We have constrained possible new interactions which produce nonrelativistic potentials between polarized neutrons and unpolarized matter proportional to $\alpha\vec{\sigma}\cdot\vec{v}$ where $\vec{\sigma}$ is the neutron spin and $\vec{v}$ is the relative velocity. We use existing data from laboratory measurements on the very long $T_{1}$ and $T_{2}$ spin relaxation times of polarized $^{3}$He gas in glass cells.Using the best available measured $T_{2}$ of polarized $^{3}$He gas atoms as the polarized source and the earth as an unpolarized source, we obtain constraints on two new interactions. We present a new experimental upper bound on possible vector-axial-vector($V_{VA}$) type interactions for ranges between $1\sim10^{8}$m. In combination with previous results, we set the most stringent experiment limits on $g_{V}g_{A}$ ranging from $\sim\mu$m to $\sim10^{8}$m. We also report what is to our knowledge the first experimental upper limit on the possible torsion fields induced by the earth on its surface. Dedicated experiments could further improve these bounds by a factor of $\sim100$. Our method of analysis also makes it possible to probe many velocity dependent interactions which depend on the spins of both neutrons and other particles which have never been searched for before experimentally.