Constraining CP Violating Nucleon-Nucleon Long-Range Interactions in Diatomic eEDM Searches.

The searches for CP violating effects in diatomic molecules, such as HfF^{+} and ThO, are typically interpreted as a probe of the electron's electric dipole moment (eEDM), a new electron-nucleon interaction, and a new electron-electron interaction. However, in the case of a nonvanishing nuclear spin, a new CP violating nucleon-nucleon long-range force will also affect the measurement, providing a new interpretation of the eEDM experimental results. Here, we use the HfF^{+} eEDM search and derive a new bound on this hypothetical interaction, which is the most stringent from terrestrial experiments in the 1 eV-10 keV mass range.