Limits on CP-violating hadronic interactions and proton EDM from paramagnetic molecules

Abstract

Abstract Experiments with paramagnetic ground or metastable excited states of molecules (ThO, HfF+, YbF, YbOH, BaF, PbO, etc.) provide strong constraints on the electron electric dipole moment (EDM) and the coupling constant C SP of contact semileptonic interaction. We compute new contributions to C SP arising from the nucleon EDMs due to the combined electric and magnetic electron-nucleon interaction. This allows us to improve limits from the experiments with paramagnetic molecules on the CP-violating parameters, such as the proton EDM, |d p | < 1.1 × 10 −23 e·cm, the QCD vacuum angle, θ ¯ $$ \left|\overline{\theta}\right| $$ < 1.4 × 10 −8, as well as the quark chromo-EDMs and the π-meson-nucleon couplings. Our results may also be used to search for the axion dark matter which produces oscillating θ ¯ $$ \overline{\theta} $$ .

Keywords

• Beyond Standard Model
• CP violation