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

5 pages, 5 figures submitted to PRL