Parity-Even and Time-Reversal-Odd Neutron Optical Potential in Spinning Matter Induced by Gravitational Torsion

TL;DR

This paper proposes a new parity-even, time-reversal-odd optical potential for neutrons in spinning matter caused by gravitational torsion, suggesting experimental methods to detect it and constrain torsion fields.

Contribution

It introduces a novel optical potential effect induced by torsion in spinning matter and discusses experimental approaches to measure and constrain torsion fields.

Findings

Potential to detect torsion-induced optical effects in neutron experiments.

Estimated experimental sensitivity to torsion fields.

Identification of systematic errors in proposed measurements.

Abstract

Recent theoretical work has shown that spin $1/2$ particles moving through unpolarized matter which sources torsion fields experience a new type of parity-even and time-reversal-odd optical potential if the matter is spinning in the lab frame. This new type of optical potential can be sought experimentally using the helicity dependence of the total cross sections for longitudinally polarized neutrons moving through a rotating cylindrical target. In combination with recent experimental constraints on short-range P--odd, T--even torsion interactions derived from polarized neutron spin rotation in matter one can derive separate constraints on the time components of scalar and pseudoscalar torsion fields in matter. We estimate the sensitivity achievable in such an experiment and briefly outline some of the potential sources of systematic error to be considered in any future experimental search for this effect.