Nuclear spin content and constraints on exotic spin-dependent couplings

TL;DR

This paper re-evaluates nuclear spin content using detailed models to improve interpretation of experimental constraints on exotic spin-dependent couplings, leading to revisions of previous limits.

Contribution

It provides a comprehensive analysis of nuclear spin content with advanced models, improving the accuracy of constraints on exotic spin couplings compared to earlier semi-empirical approaches.

Findings

Semi-empirical models are unreliable for non-valence nucleon spin predictions.

Re-analysis leads to significant revisions of existing experimental constraints.

Detailed nuclear models provide more accurate spin content data for exotic coupling searches.

Abstract

There are numerous recent and ongoing experiments employing a variety of atomic species to search for couplings of atomic spins to exotic fields. In order to meaningfully compare these experimental results, the coupling of the exotic field to the atomic spin must be interpreted in terms of the coupling to electron, proton, and neutron spins. Traditionally, constraints from atomic experiments on exotic couplings to neutron and proton spins have been derived using the single-particle Schmidt model for nuclear spin. In this model, particular atomic species are sensitive to either neutron or proton spin couplings, but not both. More recently, semi-empirical models employing nuclear magnetic moment data have been used to derive new constraints for non-valence nucleons. However, comparison of such semi-empirical models to detailed large-scale nuclear shell model calculations and analysis of known physical effects in nuclei show that existing semi-empirical models cannot reliably be used to predict the spin polarization of non-valence nucleons. The results of our re-analysis of nuclear spin content are applied to searches for exotic long-range monopole-dipole and dipole-dipole couplings of nuclei leading to significant revisions of some published constraints.