Electron Electric Dipole Moment Research Articles

Adiabatic electroweak baryogenesis driven by an axionlike particle

An axion-like particle (ALP) offers a new direction in electroweak baryogenesis because the periodic nature enables it to trigger a strong first-order phase transition insensitively to the decay constant $f$. For $f$ much above TeV, the ALP-induced electroweak phase transition is approximately described by adiabatic processes, distinguishing our scenario for electroweak baryogenesis from the conventional ones. We show that, coupled to the electroweak anomaly, the ALP can naturally realize spontaneous electroweak baryogenesis to solve the matter-antimatter asymmetry problem for $f$ in the range between about $10^5$ GeV and $10^7$ GeV. In such an ALP window, the $CP$ violation for baryogenesis is totally free from the experimental constraints, especially from the recently improved limit on the electron electric dipole moment. Future searches for ALPs could probe our scenario while revealing the connection between electroweak symmetry breaking and baryogenesis.

Second-Scale Coherence Measured at the Quantum Projection Noise Limit with Hundreds of Molecular Ions.

Cold molecules provide an excellent platform for quantum information, cold chemistry, and precision measurement. Certain molecules have enhanced sensitivity to beyond standard model physics, such as the electron's electric dipole moment (eEDM). Molecular ions are easily trappable and are therefore particularly attractive for precision measurements where sensitivity scales with interrogation time. Here, we demonstrate a spin precession measurement with second-scale coherence at the quantum projection noise (QPN) limit with hundreds of trapped molecular ions, chosen for their sensitivity to the eEDM rather than their amenability to state control and readout. Orientation-resolved resonant photodissociation allows us to simultaneously measure two quantum states with opposite eEDM sensitivity, reaching the QPN limit and fully exploiting the high count rate and long coherence.

Enhanced molecular yield from a cryogenic buffer gas beam source via excited state chemistry

We use narrow-band laser excitation of Yb atoms to substantially enhance the brightness of a cold beam of YbOH, a polyatomic molecule with high sensitivity to physics beyond the standard model (BSM). By exciting atomic Yb to the metastable 3P1 state in a cryogenic environment, we significantly increase the chemical reaction cross-section for collisions of Yb with reactants. We characterize the dependence of the enhancement on the properties of the laser light, and study the final state distribution of the YbOH products. The resulting bright, cold YbOH beam can be used to increase the statistical sensitivity in searches for new physics utilizing YbOH, such as electron electric dipole moment and nuclear magnetic quadrupole moment experiments. We also perform new quantum chemical calculations that confirm the enhanced reactivity observed in our experiment and compare reaction pathways of Yb(3P) with the reactants H2O and H2O2. More generally, our work presents a broad approach for improving experiments that use cryogenic molecular beams for laser cooling and precision measurement searches of BSM physics.

Laser-cooled polyatomic molecules for improved electron electric dipole moment searches

Doppler and Sisyphus cooling of 174YbOH are achieved and studied. This polyatomic molecule has high sensitivity to physics beyond the Standard Model and represents a new class of species for future high-precision probes of new T-violating physics. The transverse temperature of the YbOH beam is reduced by nearly two orders of magnitude to < 600 μK and the phase-space density is increased by a factor of > 6 via Sisyphus cooling. We develop a full numerical model of the laser cooling of YbOH and find excellent agreement with the data. We project that laser cooling and magneto-optical trapping of long-lived samples of YbOH molecules are within reach and these will allow a high sensitivity probe of the electric dipole moment of the electron. The approach demonstrated here is easily generalized to other isotopologues of YbOH that have enhanced sensitivity to other symmetry-violating electromagnetic moments.

The metastable Q 3Δ2 state of ThO: a new resource for the ACME electron EDM search

The best upper limit for the electron electric dipole moment was recently set by the ACME collaboration. This experiment measures an electron spin-precession in a cold beam of ThO molecules in their metastable state. Improvement in the statistical and systematic uncertainties is possible with more efficient use of molecules from the source and better magnetometry in the experiment, respectively. Here, we report measurements of several relevant properties of the long-lived state of ThO, and show that this state is a very useful resource for both these purposes. The Q state lifetime is long enough that its decay during the time of flight in the ACME beam experiment is negligible. The large electric dipole moment measured for the Q state, giving rise to a large linear Stark shift, is ideal for an electrostatic lens that increases the fraction of molecules detected downstream. The measured magnetic moment of the Q state is also large enough to be used as a sensitive co-magnetometer in ACME. Finally, we show that the Q state has a large transition dipole moment to the state, which allows for efficient population transfer between the ground state and the Q state via Stimulated Raman Adiabatic Passage (STIRAP). We demonstrate 90 % STIRAP transfer efficiency. In the course of these measurements, we also determine the magnetic moment of C state, the transition dipole moment, and branching ratios of decays from the C state.

Cancellation mechanism for the electron electric dipole moment connected with the baryon asymmetry of the Universe

We elucidate a cancellation mechanism for the electric dipole moment of the electron in the general two Higgs doublet model. The impressive improvement by the ACME Collaboration in 2018 suggests the presence of a new electron Yukawa coupling that brings in exquisite cancellations among dangerous diagrams, broadening the solution space for electroweak baryogenesis driven by an extra top Yukawa coupling. The cancellation mechanism calls for the new Yukawa couplings to have hierarchical structures that echo the observed pattern of the Standard Model Yukawa couplings.

Effects of external electric field and internuclear length on effective electric field for measurement of electron electric dipole moment

This paper studies factors which may affect the effective electric field of observation experiments of the electron electric dipole moment. Particularly, the external electric field used in experiments and the internuclear length between two atoms in polar molecules are paid attention to. YbF and ThO are chosen for polar molecules used in observational experiments of the electron electric dipole moment. For the study of the effect of the external electric field, we confirm that this external electric field is negligible in computations of the effective electric field, since this external electric field is much smaller than the internal electric field in the molecules. The effect of the internuclear length is investigated in a viewpoint of the relation with the molecular electric dipole moment.

Attaining the shot-noise-limit in the ACME measurement of the electron electric dipole moment

Experimental searches for the electron electric dipole moment, de, probe new physics beyond the Standard Model. Recently, the ACME Collaboration set a new limit of (ACME Collaboration 2018 Nature 562 355–60), constraining time reversal symmetry (T) violating physics in the 3–100 TeV energy scale. ACME extracts de from the measurement of electron spin precession due to the thorium monoxide (ThO) molecule’s internal electric field. This recent ACME II measurement achieved an order of magnitude increased sensitivity over ACME I by reducing both statistical and systematic uncertainties in the measurement of the electric dipole precession frequency. The ACME II statistical uncertainty was a factor of 1.7 above the ideal shot-noise limit. We have since traced this excess noise to timing imperfections. When the experimental imperfections are eliminated, we show that shot noise limit is attained by acquiring noise-free data in the same configuration as ACME II.

Electric dipole moments from dark sectors

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 $\ensuremath{\epsilon}$. 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.

Electroweak baryogenesis with vector-like leptons and scalar singlets

We investigate the viability of electroweak baryogenesis in a model with a first order electroweak phase transition induced by the addition of two gauge singlet scalars. A vector-like lepton doublet is introduced in order to provide CP violating interactions with the singlets and Standard Model leptons, and the asymmetry generation dynamics are examined using the vacuum expectation value insertion approximation. We find that such a model is readily capable of generating sufficient baryon asymmetry while satisfying electron electric dipole moment and collider phenomenology constraints.

Constraining CP-violating electron-gluonic operators

We present an analysis of constraints on two types of CP-odd electron-gluonic operators (ēiγ5e)GμνaGaμν and left(overline{e}eright){G}_{mu nu}^a{overset{sim }{G}}^{amu nu } from current and future electric dipole moment (EDM) experiments. The recent result from the ACME experiment using ThO molecules is used to derive an impressive lower bound on the effective scale for (ēiγ5e)GμνaGaμν at 8 TeV, assuming a QCD one-loop factor and no helicity suppression from new physics. One interesting aspect is that (ēiγ5e)GμνaGaμν contributes to the observable EDM in ThO experiment mainly through CP-odd electron-nucleon interaction rather than direct electron EDM which arises from three-loop running and matching. For left(overline{e}eright){G}_{mu nu}^a{overset{sim }{G}}^{amu nu } the current bound is much weaker and suffers from large uncertainties. We also discuss the QCD running and matching for the CP-odd electron-gluonic operators and give an estimate of the relevant nucleon matrix elements and uncertainties that are needed in the calculation.

Optical Rotation Approach to Search for the Electric Dipole Moment of the Electron

The P , T -odd Faraday effect (i.e., rotation of the polarization plane of light propagating through a medium in presence of the external electric field due to P , T symmetry violating interactions) is considered for several atomic species: Ra, Pb, Tl, Hg, Cs, and Xe. Corresponding theoretical simulation of P , T -odd Faraday experiment, with already achieved intracavity absorption spectroscopy characteristics and parameters, is performed. The results show that the magnetic dipole transitions in the Tl and Pb atoms as well as the electric dipole transitions in the Ra, Hg and Cs atoms are favorable for the observation of the P , T -odd Faraday optical rotation. The estimation of the rotation angle of the light polarization plane demonstrates that recently existing boundaries for the electron electric dipole moment can be improved by one-two orders of magnitude.

Enhanced sensitivity of the electron electric dipole moment from YbOH: The role of theory

The prospect of laser cooling of polyatomic molecules has opened a new avenue in the search for the electric dipole moment of the electron (eEDM). An upper bound on the eEDM would probe new physics arising from beyond the Standard Model of elementary particles. In this work, we report the first theoretical results for the effective electric field experienced by the electron in YbOH, and its molecular electric dipole moment, using a relativistic coupled cluster theory. We compare these two properties of YbOH with YbF, which also has a singly unoccupied orbital on the Yb ion. We also present the results of the effective electric field for different bond angles, which sheds light on the sensitivity that can be expected from an eEDM experiment with YbOH.

RaH as a potential candidate for electron electric-dipole-moment searches

Diatomic polar molecules have been the focus of research in the recent past as candidates for electron electric dipole moment (eEDM), de, measurements. In the present work, we focus on RaH molecule and have calculated three of its properties (in the X2Σ+ state) the effective electric field (Eeff), the scalar-pseudoscalar (S-PS) interaction coefficient (Ws,A), and permanent electric dipole moment (PDM) that play crucial roles in probing fundamental symmetry violations. The calculations were based on the relativistic coupled-cluster singles and doubles (RCCSD) frame work. Our results for Eeff, Ws,A, and PDM are 80.31 GV/cm, 216.82 kHz, and 4.44 D respectively. In addition to possessing high magnitudes of Eeff and Ws,A, RaH also has a large PDM, which is a highly desirable criterion for eEDM experiments. The analysis of our results clearly indicates the spectacular role of electron correlation in enhancing their magnitudes ≈16% for PDM and ≈31% for Eeff and Ws,A. The ratio of Eeff to Ws,A for RaH is 89.56×1018e−1 cm−1. Based on our results and other experimental considerations, we propose RaH as a future candidate for experiments in this field.

Enhancement factor for the electric dipole moment of the electron in the BaOH and YbOH molecules

Polyatomic polar molecules are promising systems for future experiments that search for violation of time-reversal and parity symmetries due to their advantageous electronic and vibrational structure, which allows laser cooling, full polarisation of the molecule, and reduction of systematic effects [I. Kozyryev and N.R. Hutzler, Phys, Rev. Lett. {\bf 119}, 133002 (2017)]. In this work we investigate the enhancement factor of the electric dipole moment of the electron ($E_\text{eff}$) in the triatomic monohydroxide molecules BaOH and YbOH within the high-accuracy relativistic coupled cluster method. The recommended $E_\text{eff}$ values of the two systems are 6.65 $\pm$ 0.15 GV/cm and 23.4 $\pm$ 1.0 GV/cm, respectively. We compare our results with similar calculations for the isoelectronic diatomic molecules BaF and YbF, which are currently used in experimental search for $P,T$-odd effects in molecules. The $E_\text{eff}$ values prove to be very close, within about 1.5 $\%$ difference in magnitude between the diatomic and the triatomic compounds. Thus, BaOH and YbOH have a similar enhancement of the electron electric dipole moment, while benefiting from experimental advantages, and can serve as excellent candidates for next-generation experiments.

Interference between the E1 and M1 Amplitudes of the Transition from the H State to C of a ThO Molecule

The systematic error in experiments concerning searching for the electric dipole moment of an electron due to the Stark interference between the E1 and M1 amplitudes of the transition from the $${{H}^{3}}{{\Delta }_{1}}$$ state to $${{C}^{1}}\Pi $$ of a ThO molecule has been calculated. The calculations show that the error is about three orders of magnitude lower than the current limitation on the electric dipole moment of electron.

Development of a Dual Isotope Co-Magnetometer Using Laser Cooled Rubidium Toward Electron Electric Dipole Moment Measurement Using Francium

We have developed a dual-rubidium-isotope magneto-optical tap (MOT) for a dual species co-magnetometer used in measurements of the electron electric dipole moment (EDM) using laser-cooled francium atoms. The EDM measurement using atoms in an optical dipole force trap exhibits the advantage of less Doppler effects and longer interaction time compared to atomic and molecular beam experiments. In EDM experiments, the fluctuation of the magnetic field and the vector light shift induced by an optical dipole force can cause systematic errors. The dual species co-magnetometer is being developed to simultaneously monitor the fluctuations of both the magnetic field and the vector light shift. We demonstrated the dual-rubidium-isotope MOT for the development of the dual species co-magnetometer.

EFT approach to the electron electric dipole moment at the two-loop level

The ACME collaboration has recently reported a new bound on the electric dipole moment (EDM) of the electron, |de| < 1.1 × 10−29 e · cm at 90% confidence level, reaching an unprecedented accuracy level. This can translate into new relevant constraints on theories beyond the SM laying at the TeV scale, even when they contribute to the electron EDM at the two-loop level. We use the EFT approach to classify these corrections, presenting the contributions to the anomalous dimension of the CP-violating dipole operators of the electron up to the two-loop level. Selection rules based on helicity and CP play an important role to simplify this analysis. We use this result to provide new bounds on BSM with leptoquarks, extra Higgs, or constraints in sectors of the MSSM and composite Higgs models. The new ACME bound pushes natural theories significantly more into fine-tune territory, unless they have a way to accidentally preserve CP.

Nuclear parity- and time-reversal-symmetry violation in the HgH201 molecule

Investigation of the nuclear magnetic quadrupole moment (MQM) is an excellent way to reveal the new physics in the hadron sector of matter. Therefore, we investigate the violation of parity ($\mathcal{P}$) and time-reversal ($\mathcal{T}$) invariance induced by the MQM of the $^{201}\mathrm{Hg}$ nucleus in the HgH molecule, which has been proposed as a very promising candidate for the experimental search of the electric dipole moment of electron [M. G. Kozlov and A. Derevianko, Phys. Rev. Lett. 97, 063001 (2006)]. We report the precise value of the molecular parameter, ${W}_{\text{M}}$, associated with the $\mathcal{P},\mathcal{T}$-odd nuclear MQM-electron interaction in $^{201}\mathrm{HgH}$ using the four-component relativistic coupled-cluster method. This parameter is required to interpret the experimental $\mathcal{P},\mathcal{T}$-odd frequency shift in terms of the MQM of nuclei. Furthermore, the magnetic hyperfine structure (HFS) constants of the molecule are computed at the same level of theory. We also study the role of core-correlating functions and the virtual energy functions in the calculations of the HFS constant and ${W}_{\text{M}}$. The most reliable value of ${W}_{\text{M}}$ in HgH is obtained as $3.22\ifmmode\times\else\texttimes\fi{}{10}^{33}$ Hz/$e$ ${\mathrm{cm}}^{2}$ with an uncertainty of around 6%.

Current status and future prospects of the singlet-doublet dark matter model with CP violation

We discuss the singlet-doublet fermion dark matter model with CP-violation. In this model, the CP-violation generates a pseudo-scalar interaction of dark matter with the SM-Higgs boson. Thanks to the pseudo-scalar interaction, the model can evade the strong constraint from the dark matter direct detection experiments while keeping the success of the thermal relic scenario. The CP-violation also predicts signals in dark matter indirect detection experiments and electric dipole moments (EDM) that can be as large as the current upper bound. We investigate the constraints and prospects of the direct detection experiments, the indirect detection experiment, and the electron EDM. We also investigate the stability of the Higgs potential. Combining these observables, we find that heavy dark matter is disfavored. We also find it is possible to probe the Higgs funnel region by the combination of the direct detection experiments and the measurements of the electron EDM if experiments for the electron EDM reach to $O(10^{ -32})$ e cm in future.