Short-Range, Spin-Dependent Interactions of Electrons: A Probe for Exotic Pseudo-Goldstone Bosons

Abstract

We used a torsion pendulum and rotating attractor with 20-pole electron-spin distributions to probe dipole-dipole interactions mediated by exotic pseudo-Goldstone bosons with ${m}_{b}{c}^{2}\ensuremath{\le}500\text{ }\text{ }\ensuremath{\mu}\mathrm{eV}$ and coupling strengths up to 14 orders of magnitude weaker than electromagnetism. This corresponds to symmetry-breaking scales $F\ensuremath{\le}70\text{ }\text{ }\mathrm{TeV}$, the highest reached in any laboratory experiment. We used an attractor with a 20-pole unpolarized mass distribution to improve laboratory bounds on $CP$-violating monopole-dipole forces with $1.5\text{ }\text{ }\ensuremath{\mu}\mathrm{eV}<{m}_{b}{c}^{2}<400\text{ }\text{ }\ensuremath{\mu}\mathrm{eV}$ by up to a factor of 1000.