Limits on the Axial Coupling Constant of New Light Bosons

TL;DR

This paper reports the first experimental upper limit on the axial coupling constant of a hypothetical light boson mediating a new force between neutrons and protons, using neutron spin precession measurements.

Contribution

It provides the first direct experimental constraint on the axial coupling constant of a new light spin 1 boson in the millimeter range.

Findings

Upper limit of $g_A^2$ at $6\times10^{-13}$ (95% C.L.) for 1 mm range

Set constraints on new force mediated by light bosons

Used Ramsey's technique with cold neutrons

Abstract

We report on a neutron particle physics experiment, which provides for the first time an upper limit on the strength of an axial coupling constant for a new light spin 1 boson in the millimeter range. Such a new boson would mediate a new force between ordinary fermions, like neutrons and protons. The experiment was set up at the cold neutron reflectometer Narziss at the Paul Scherrer Institute and uses Ramsey's technique of separated oscillating fields to search for a pseudomagnetic neutron spin precession induced by this new interaction. For the axial coupling constant $g_A^2$, an upper limit of $6\times10^{-13}$ (95% C.L.) was determined for an interaction range of 1 mm.