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Register a new userBounds on new physics from electric dipole moments
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Authors
Martin Jung
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Electric dipole moments are extremely sensitive probes for additional sources of CP violation in new physics models. The multi-scale problem of relating the high-precision measurements with neutrons, atoms and molecules to fundamental parameters can be approached model-independently to a large extent; however, care must be taken to include the uncertainties from especially nuclear and QCD calculations properly. The resulting bounds on fundamental parameters are illustrated in the context of Two-Higgs-Doublet models.
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We examine the sensitivity of electric dipole moments (EDMs) to new $CP$-violating physics in a hidden (or dark) sector, neutral under the Standard Model (SM) gauge groups, and coupled via renormalizable portals. In the absence of weak sector interactions, we show that the electron EDM can be induced purely through the gauge kinetic mixing portal, but requires five loops, and four powers of the kinetic mixing parameter $epsilon$. Allowing weak interactions, and incorporating the Higgs and neutrino portals, we show that the leading contributions to $d_e$ arise at two-loop order, with the main source of $CP$-violating being in the interaction of dark Higgs and heavy singlet neutrinos. In such models, EDMs can provide new sensitivity to portal couplings that is complementary to direct probes at the intensity frontier or high energy colliders.
We consider a model in which baryogenesis occurs at low scale, at a temperature below the electroweak phase transition. This model involves new diquark-type scalars which carry baryon number. Baryon number violation is introduced in the scalar potential, permitting $Delta B=2$ violating process involving Standard Model quarks while avoiding stringent proton decay constraints. Depending on their quantum number assignment, the diquark-type scalars can couple to either right or left handed quarks, or to both. We show that this model can provide a viable explanation of the baryon asymmetry of the universe provided that the coupling to left handed quarks are present. However, the coexistence of couplings to left and right handed quarks introduces important phenomenological constraints on the model, such as radiative contributions to quark masses and the generation of electric dipole moments for nuclei, which probe the CP even and CP odd products of the relevant couplings constants, respectively. We demonstrate that the strongest such constraints arise from electric dipole moment measurements of the neutron and $^{199}$Hg. These constraints are sufficiently strong that, in the absence of an intricate flavor structure, baryogenesis must be dominated by the couplings of the new scalars to left handed quarks.
The electric dipole moments (EDMs) of nucleons are sensitive probes of additional $cal CP$ 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 $cal CP$ violation sources from new physics beyond the electroweak scale. We obtain the current limits on quark EDMs as $1.27times10^{-24},ecdot{rm cm}$ for the up quark and $1.17times10^{-24},ecdot{rm cm}$ for the down quark at the scale of $4,rm GeV^2$. 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 three orders of magnitude leading to a much more sensitive probe of new physics models.
Searches for permanent electric dipole moments of fundamental particles and systems with spin are the experiments most sensitive to new CP violating physics and a top priority of a growing international community. We briefly review the current status of the field emphasizing on the charged leptons and lightest baryons.
We analyze the implications of CP-violating scalar leptoquark (LQ) interactions for experimental probes of parity- and time-reversal violating properties of polar molecules. These systems are predominantly sensitive to the electric dipole moment (EDM) of the electron and nuclear-spin-independent (NSID) electron-nucleon interaction. The LQ model can generate both a tree-level NSID interaction as well as the electron EDM at one-loop order. Including both interactions, we find that the NSID interaction can dominate the molecular response. For moderate values of couplings, the current experimental results give roughly two orders of magnitude stronger limits on the electron EDM than one would otherwise infer from a sole-source analysis.
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