Experiments searching for the electric dipole moment (EDM) of the electron de utilize atomic/molecular states with one or more uncompensated electron spins, and these paramagnetic systems have recently achieved remarkable sensitivity to de. If the source of CP violation resides entirely in the hadronic sector, the two-photon exchange processes between electrons and the nucleus induce CP-odd semileptonic interactions, parametrized by the Wilson coefficient CSP, and provide the dominant source of EDMs in paramagnetic systems instead of de. We evaluate the CSP coefficients induced by the leading hadronic sources of CP violation, namely, nucleon EDMs and CP-odd pion-nucleon couplings, by calculating the nucleon-number-enhanced CP-odd nuclear scalar polarizability, employing chiral perturbation theory at the nucleon level and the Fermi-gas model for the nucleus. This allows us to translate the ACME EDM limits from paramagnetic ThO into novel-independent constraints on the QCD theta term |θ¯|<3×10-8, proton EDM |dp|<2×10-23 e cm, isoscalar CP-odd pion-nucleon coupling |g¯πNN(1)|<4×10-10, and color EDMs of quarks |du-dd|<2×10-24 cm. We note that further experimental progress with EDM experiments in paramagnetic systems may allow them to rival the sensitivity of EDM experiments with neutrons and diamagnetic atoms to these quantities.
Bibliographical noteFunding Information:
M. P. is grateful to Dr. A. Dutt-Mazumder, his late friend for collaboration over a decade ago on unpublished work considering nucleon polarizabilities and EDMs. The authors also thank Dr. M. Voloshin for helpful discussions. The work of M. P. and A. R. was supported in part by NSERC, Canada. Research at the Perimeter Institute is supported in part by the Government of Canada through NSERC and by the Province of Ontario through the Ministry of Economic Development, Job Creation and Trade (MEDT). Y. V. S. was supported by a Humboldt Research Fellowship from the Alexander von Humboldt Foundation, by the World Premier International Research Center Initiative, MEXT, Japan, and by the JSPS KAKENHI Grant No. 20K14460.