  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 $m_{\rm b}\leq 500 \; \mu$eV and coupling
strengths up to 14 orders of magnitude weaker than electromagnetism. This
corresponds to symmetry-breaking scales $F \leq 70$ 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
interactions with $1.5\:\mu$eV$<m_{\rm b}<400\:\mu$eV by a factor of up to
1000.

High Energy Physics - Experiment;Instrumentation and Detectors