Abstract
The electric dipole moments (EDMs) of nucleons are sensitive probes of additional $CP$ violation sources beyond the standard model to account for the baryon number asymmetry of the universe. As a fundamental quantity of the nucleon structure, tensor charge is also a bridge that relates nucleon EDMs to quark EDMs. With a combination of nucleon EDM measurements and tensor charge extractions, we investigate the experimental constraint on quark EDMs, and its sensitivity to $CP$ violation sources from new physics beyond the electroweak scale. We obtain the current limits on quark EDMs as $1.27\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}\text{ }\text{ }e\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{cm}$ for the up quark and $1.17\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}\text{ }\text{ }e\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{cm}$ for the down quark at the scale of $4\text{ }\text{ }{\mathrm{GeV}}^{2}$. We also study the impact of future nucleon EDM and tensor charge measurements, and show that upcoming new experiments will improve the constraint on quark EDMs by about 3 orders of magnitude leading to a much more sensitive probe of new physics models.
Highlights
Symmetries play a central role in physics
With a combination of nucleon electric dipole moments (EDMs) measurements and tensor charge extractions, we investigate the experimental constraint on quark EDMs, and its sensitivity to CP violation sources from new physics beyond the electroweak scale
We investigate the experimental constraint on quark EDMs by combining nucleon EDM measurements and tensor charge extractions
Summary
Charge conjugate (C), parity (P), and time reversal (T), were believed to be conserved until the discovery of parity violation in weak interactions suggested by Lee and Yang [1] and confirmed in nuclear beta decays [2] and successive meson decays [3] It is a cornerstone of the standard model (SM) of particle physics. The first term, a dimension-four operator, is allowed in the standard model as the QCD θ-term, where the overall phase of the quark mass matrix is absorbed into θ It could in principle generate large hadronic EDMs, but the upper limit on the neutron EDM constrains the coefficient to jθj ≤ 10−10.
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