Hyperfine structure interval of the2sstate of hydrogenlike atoms and a constraint on a pseudovector boson with mass below 1 keV/c2

Abstract

A constraint on a spin-dependent interaction, induced by a pseudovector light boson, is presented. The interaction includes a Yukawa-type contribution $\ensuremath{\alpha}{}^{\ensuremath{''}}({\mathbf{s}}_{1}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathbf{s}}_{2}){e}^{\ensuremath{-}\ensuremath{\lambda}r}/r$ and a contact spin-spin term. To disentangle the long-range and contact terms we utilize experimental data on the $1s$ and $2s$ hyperfine intervals for light two-body atoms and construct a specific difference $8\ifmmode\times\else\texttimes\fi{}{E}_{\mathrm{hfs}}(2s)\ensuremath{-}{E}_{\mathrm{hfs}}(1s)$. That allows one to constrain the spin-dependent coupling constant $\ensuremath{\alpha}{}^{\ensuremath{''}}$ of an electron-nucleus Yukawa-type interaction in hydrogen, deuterium, and the helium-3 ion at the level below a part in ${10}^{16}$. The derived constraint is related to the range of masses below $4 \mathrm{keV}/{c}^{2}$. The combined constraint including the contact terms is also presented.