Hadronic Electric Dipole Moments Research Articles

An ϵ′ improvement from right-handed currents

Recent lattice QCD calculations of direct CP violation in $K_L \to \pi \pi$ decays indicate tension with the experimental results. Assuming this tension to be real, we investigate a possible beyond-the-Standard Model explanation via right-handed charged currents. By using chiral perturbation theory in combination with lattice QCD results, we accurately calculate the modification of $\epsilon'/\epsilon$ induced by right-handed charged currents and extract values of the couplings that are necessary to explain the discrepancy, pointing to a scale around $10^2$ TeV. We find that couplings of this size are not in conflict with constraints from other precision experiments, but next-generation hadronic electric dipole moment searches (such as neutron and ${}^{225}$Ra) can falsify this scenario. We work out in detail a direct link, based on chiral perturbation theory, between CP violation in the kaon sector and electric dipole moments induced by right-handed currents which can be used in future analyses of left-right symmetric models.

Storage Ring EDM Experiments

Dedicated storage ring electric dipole moment (EDM) methods show great promise advancing the sensitivity level by a couple orders of magnitude over currently planned hadronic EDM experiments. We describe the present status and recent updates of the field.

Sensitivity to light weakly-coupled new physics at the precision frontier

Precision measurements of rare particle physics phenomena (flavor oscillations and decays, electric dipole moments, etc.) are often sensitive to the effects of new physics encoded in higher-dimensional operators with Wilson coefficients given by $\mathrm{C}/({\mathrm{\ensuremath{\Lambda}}}_{\mathrm{NP}}{)}^{n}$, where C is dimensionless, $n\ensuremath{\ge}1$, and ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{NP}}$ is an energy scale. Many extensions of the Standard Model predict that ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{NP}}$ should be at the electroweak scale or above, and the search for new short-distance physics is often stated as the primary goal of experiments at the precision frontier. In rather general terms, we investigate the alternative possibility---$\mathrm{C}\ensuremath{\ll}1$, and ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{NP}}\ensuremath{\ll}{m}_{W}$---to identify classes of precision measurements sensitive to light new physics (hidden sectors) that do not require an ultraviolet completion with additional states at or above the electroweak scale. We find that hadronic electric dipole moments, lepton number and flavor violation, nonuniversality, as well as lepton $g\ensuremath{-}2$ can be induced at interesting levels by hidden sectors with light degrees of freedom. In contrast, many hadronic flavor- and baryon number-violating observables, and precision probes of charged currents, typically require new physics with ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{NP}}\ensuremath{\gtrsim}{m}_{W}$. Among the leptonic observables, we find that a nonzero electron electric dipole moment near the current level of sensitivity would point to the existence of new physics at or above the electroweak scale.

Searching for t → c(u)h with dipole moments

A discovery of flavour-changing Higgs-boson decays would constitute an undeniable signal of new physics. We derive model-independent constraints on the tch and tuh couplings that arise from the bounds on hadronic electric dipole moments. Comparisons of the present and future sensitivities with both the direct LHC constraints and the indirect limits from D-meson physics are also presented.

QCD corrections to quark (chromo)electric dipole moments in high-scale supersymmetry

Recent results from the LHC experiments, both for the Higgs mass measurement and the direct search for supersymmetric (SUSY) particles, might indicate that the SUSY breaking scale is much higher than the electroweak scale. Although it is difficult to investigate such a scenario at collider experiments, the measurement of the hadronic electric dipole moments is one of promising ways to detect the effects of the SUSY particles. These effects are expressed in terms of the CP-violating effective operators defined at the SUSY breaking scale, which involve quarks, gluons, photons, and gluinos. In this paper, we discuss the QCD corrections to the effective operators in the high-scale SUSY scenario. To appropriately evaluate the radiative corrections in the presence of large mass hierarchy among the SUSY particles, we exploit an effective theoretical approach based on the renormalization-group equations. As a result, it is found that the low-energy quark electric and chromoelectric dipole moments may differ from those evaluated in previous works by $ \mathcal{O} $ (100) % and $ \mathcal{O} $ (10) %, respectively.

A lower bound on hadronic EDMs from CP violation in [formula omitted] mixing in SUSY alignment models

The SM predictions for CP violating effects in D meson systems are highly suppressed at the per mill level. Therefore, any experimental evidence for a sizable CP violation in D0–D¯0 mixing would unambiguously point towards a New Physics (NP) signal. Within supersymmetric scenarios, the popular alignment models can naturally account for large, non-standard effects in D0–D¯0 mixing. We demonstrate that, within alignment models, detectable CP violating effects in D0–D¯0 mixing would unambiguously imply a lower bound for the electric dipole moment (EDM) of hadronic systems, like the neutron EDM and the mercury EDM, in the reach of future experimental sensitivities. The simultaneous evidence of CP violation in D meson systems together with non-vanishing hadronic EDMs would strongly support the idea of SUSY alignment models and disfavour gauge-mediated SUSY breaking models, SUSY models with MFV and non-Abelian SUSY flavour models. As a byproduct of our analysis, we study the correlation between the time dependent CP asymmetry in decays to CP eigenstates Sf and the semileptonic asymmetry aSL both model independently and in SUSY alignment models.

Electric dipole moments from flavor-changing supersymmetric soft terms

The standard model predictions for the hadronic electric dipole moments (EDMs) are well far from the present experimental resolutions, thus, the EDMs represent very clean probes of New Physics (effects. Especially, within a minimal supersymmetric standard model framework with flavor-changing (but not necessarily $CP$-violating) soft terms, large and potentially visible effects to the EDMs are typically expected. In this paper we point out that, beyond-leading-order effects, so far neglected in the literature, dominate over the leading-order effects in large regions of the parameter space; hence, their inclusion in the evaluation of the hadronic EDMs is unavoidable.

New two-loop contributions to hadronic EDMs in the MSSM

Flavor-changing terms with CP-violating phases in the quark sector may contribute to the hadronic electric dipole moments (EDMs). However, within the Standard Model (SM), the source of CP violation comes from the unique CKM phase, and it turns out that the EDMs are strongly suppressed. This implies that the EDMs are very sensitive to non-minimal flavor violation structures of theories beyond the SM. In this paper, we discuss the quark EDMs and CEDMs (chromoelectric dipole moments) in the MSSM with general flavor-changing terms in the squark mass matrices. In particular, the charged-Higgs mediated contributions to the down-quark EDM and CEDM are evaluated at two-loop level. We point out that these two-loop contributions may dominate over the one-loop induced gluino or Higgsino contributions even when the squark and gluino masses are around few TeV and \tan\beta is moderate.

Hadronic electric dipole moments inR-parity violating supersymmetry

We calculate the electric dipole moments (EDM) of the neutral {sup 199}Hg atom, neutron and deuteron within a generic R-parity violating SUSY model (Re{sub p} SUSY) on the basis of a one-pion-exchange model with CP-odd pion-nucleon interactions. We consider two types of the Re{sub p} SUSY contributions to the above hadronic EDMs: via the quark chromoelectric dipole moments (CEDM) and CP-violating 4-quark interactions. We demonstrate that the former contributes to all the three studied EDMs while the latter appears only in the nuclear EDMs via the CP-odd nuclear forces. We find that the Re{sub p} SUSY induced 4-quark interactions arise at tree level through the sneutrino exchange and involve only s and b quarks. Therefore, their effect in hadronic EDMs is determined by the strange and bottom-quark sea of the nucleon. From the null experimental results on the hadronic EDMs we derive the limits on the imaginary parts of certain products Im({lambda}{sup '}{lambda}{sup '}*) of the trilinear Re{sub p}-couplings and show that the currently best limits come from the {sup 199}Hg EDM experiments. We demonstrate that some of these limits are better than those existing in the literature. We argue that future storage ring experiments on the deuteron EDM aremore » able to improve these limits by several orders of magnitude.« less

Hadronic EDM constraints on orbifold GUTs

We point out that the null results of the hadronic electric dipole moment (EDM) searches constrain orbifold grand unified theories (GUTs), where the GUT symmetry and supersymmetry (SUSY) are both broken by boundary conditions in extra dimensions and it leads to rich fermion and sfermion flavor structures. A marginal chromoelectric dipole moment (CEDM) of the up quark is induced by the misalignment between the CP violating left- and right-handed up-type squark mixings, in contrast to the conventional four-dimensional SUSY GUTs. The up quark CEDM constraint is found to be as strong as those from charged lepton flavor violation (LFV) searches. The interplay between future EDM and LFV experiments will probe the structures of the GUTs and the SUSY breaking mediation mechanism.

Electric dipole moments as probes of new physics

We review several aspects of flavour-diagonal CP-violation, focussing on the role played by the electric dipole moments (EDMs) of leptons, nucleons, atoms, and molecules, which constitute the source of several stringent constraints on new CP-violating physics. We dwell specifically on the calculational aspects of applying the hadronic EDM constraints, reviewing in detail the application of QCD sum-rules to the calculation of nucleon EDMs and CP-odd pion–nucleon couplings. We also consider the current status of EDMs in the Standard Model, and on the ensuing constraints on the underlying sources of CP-violation in physics beyond the Standard Model, focussing on weak-scale supersymmetry.

Hadronic electric dipole moments induced by strangeness and constraints on supersymmetricCPphases

We consider hadronic CP violation induced by chromoelectric dipolemoments (CEDMs) of light quarks and the QCD theta parameter ($?overline{?theta}$). We concentrate on the strange quark CEDM especially in this paper. Using effective CP violating nucleon interactions induced by the CEDMs and $?overline{?theta}$ with the SU(3) chiral Lagrangian technique, we calculate the EDMs for the $^{199}$Hg atom, neutron and deuteron. We also discuss supersymmetric contributions to the electric dipole moments with the mass insertion approximations and give stringent constraints on the CP phases of the flavor changing SUSY breaking terms.

Hadronic electric dipole moments, the Weinberg operator, and light gluinos

We reexamine questions concerning the contribution of the three-gluon Weinberg operator to the electric dipole moment of the neutron, and provide several QCD sum-rule-based arguments that the result is smaller than---but nevertheless consistent with---estimates which invoke naive dimensional analysis. We also point out a regime of the minimal supersymmetric standard model parameter space with light gluinos for which this operator provides the dominant contribution to the neutron electric dipole moment due to enhancement via the dimension five color electric dipole moment of the gluino.

Hadron electric dipole moments from CP-odd operators of dimension five via QCD sum rules: the vector meson

We present a complete analysis of the electric dipole moment (EDM) of the ρ-meson induced by CP violating operators of dimension 4 and 5 within the QCD sum rules approach. The set of CP-odd operators includes the theta term and the electric and chromoelectric dipole moments of the three light quarks. We find that the ρ-meson EDM induced purely by the EDMs of quarks is smaller than, but still in reasonable agreement with, the predictions of a naive constituent quark model. However, the chromoelectric dipole moments, including that of the strange quark, give comparable and sometimes larger contributions. We also consider the effect on the hadronic EDM of the existence of Peccei-Quinn symmetry. When this symmetry is active, chromoelectric dipole moments induce a linear term in the axion potential which leads to a numerically important vacuum contribution to the hadronic EDM.