Thursday·April 23, 2020

[Submitted on 22 Apr 2020] (cross-list from hep-ph)

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

V. V. Flambaum🇦🇺 · I. B. Samsonov🇦🇺 · H. B. Tran Tan🇦🇺

Experiments with paramagnetic ground or metastable excited states of molecules (ThO, HfF${}^{+}$, YbF, YbOH, BaF, PbO, etc.) provide strong constraints on electron electric dipole moment (EDM) and coupling constant $C_{SP}$ of contact semileptonic interaction. We compute new contributions to $C_{SP}$ arising from the nucleon EDMs due to 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, $|d_p|<1.1\times 10^{-23}e\cdot$cm, the QCD vacuum angle, $|\bar{\theta }|<1.4\times 10^{-8}$, as well as the quark chromo-EDMs and $\pi$-meson-nucleon couplings. Our results may also be used to search for the axion dark matter which produces oscillating $\bar{\theta }$.