Axion-mediated monopole-dipole nucleon force at submillimeter range

For the monopole-dipole potential $V(r) = g_s^{N} g_p^{N} (\hbar^2/(8 \pi m_N)) (\sigma . r_{\mathrm{hat}}) (1/(\lambda r) + 1/r^2) \exp(-r/\lambda)$ between an unpolarized nucleon and a polarized nucleon (Moody-Wilczek form), with range $\lambda$ from $10\,\text{micron}\ \text{to}\ 1\,\mathrm{mm}$, determine whether $g_s^{N} g_p^{N}$ is nonzero down to the value expected for a QCD axion with a small CP-violating scalar coupling, using polarized He-3 or other nuclear-spin sensors near a modulated source mass (Arvanitaki and Geraci 2014).

A resonant nuclear-spin measurement near a modulated source mass that reaches the QCD-axion band in $g_{s}^{N} g_{p}^{N}$ over this range, or detects a signal with the predicted distance dependence.