Improving Limits on Anomalous Pseudoscalar Interactions using Few Body Calculations

Exotic long-range spin-dependent interactions between nucleons can be generated by many possible sources beyond the Standard Model. Anomalous interactions arising from exchange of ultralight bosons with pseudoscalar couplings g$_{P}$ between free fermions are highly suppressed in the nonrelativistic limit due to their spin dependence and suppression factors associated with the parity change at the vertex. As a consequence the experimental limits on such interactions are several orders of magnitude weaker than limits on spin-independent Yukawa interactions. We call attention to a physical process in the interaction between nucleons in separate nuclei exchanging a light pseudoscalar first identified by Krause and Fischbach\footnote{Krause, D., et. al. (1993). Proceedings of the XXVIIIth Rencontre De Moriond. p.455.} which can lead to a spin independent effect and, in combination with existing experimental constraints on exotic Yukawa interactions, can improve constraints on g$_{P}$ for interaction ranges of atomic and mesoscopic scales. Similar nuclei models can also be used to improve constraints on P and T odd long-range interactions between scalar and pseudoscalar vertices.The theoretical evaluations of this effect will require knowledge of parity-odd matrix elements in nuclei.