Search For Electric Dipole Moment Research Articles

Sterile neutrino dark matter within the νSMEFT

Sterile neutrinos with masses at the keV scale and mixing to the active neutrinos offer an elegant explanation of the observed dark matter (DM) density. However, the very same mixing inevitably leads to radiative photon emission and the non-observation of such peaked X-ray lines rules out this minimal sterile neutrino DM hypothesis. We show that in the context of the Standard Model effective field theory with sterile neutrinos (νSMEFT), higher dimensional operators can produce sterile neutrino DM in a broad range of parameter space. In particular, νSMEFT interactions can open the large mixing parameter space due to their destructive interference, through operator mixing or matching, in the X-ray emission. We also find that, even in the zero mixing limit, the DM density can always be explained by νSMEFT operators. The testability of the studied νSMEFT operators in searches for electric dipole moments, neutrinoless double beta decay, and pion decay measurements is discussed.

Spin-precession method for sensitive electric dipole moment searches

Spin-precession method for sensitive electric dipole moment searches

Electric charging effects on insulating surfaces in cryogenic liquids.

This paper presents a new technique to study the adsorption and desorption of ions and electrons on insulating surfaces in the presence of strong electric fields in cryoliquids. The experimental design consists of a compact cryostat coupled with a sensitive electro-optical Kerr device to monitor the stability of the electric fields. The behavior of nitrogen and helium ions on a poly(methyl methacrylate) (PMMA) surface was compared to a PMMA surface coated with a mixture of deuterated polystyrene and deuterated polybutadiene. Ion accumulation and removal on these surfaces were unambiguously observed. Within the precision of the data, both surfaces behave similarly for the physisorbed ions. The setup was also used to measure the (quasi-)static dielectric constant of PMMA at T ≈ 70K. The impact of the ion adsorption on the search for a neutron permanent electric dipole moment in a cryogenic environment, such as the nEDM@SNS experiment, is discussed.

Anomalous spin precession systematic effects in the search for a muon EDM using the frozen-spin technique

At the Paul Scherrer Institut (PSI), we are developing a high-precision apparatus with the aim of searching for the muon electric dipole moment (EDM) with unprecedented sensitivity. The underpinning principle of this experiment is the frozen-spin technique, a method that suppresses the spin precession due to the anomalous magnetic moment, thereby enhancing the signal-to-noise ratio for EDM signals. This increased sensitivity enables measurements that would be difficult to achieve with conventional g-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g - 2$$\\end{document} muon storage rings. Given the availability of the 125MeV/c\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${125}\\,{\ extrm{MeV}/\ extit{c}}$$\\end{document} muon beam at PSI, the anticipated statistical sensitivity for the EDM after a year of data collection is 6×10-23e·cm.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${6\ imes 10^{-23}}\\,{e\\!\\cdot \\!\ extrm{cm}}.$$\\end{document} To achieve this goal, it is imperative to do a detailed analysis of any potential spurious effects that could mimic EDM signals. In this study, we present a quantitative methodology to evaluate the systematic effects that might arise in the context of the frozen-spin technique utilised within a compact storage ring. Our approach involves the analytical derivation of equations governing the motion of the muon spin in the electromagnetic (EM) fields intrinsic to the experimental setup, validated through numerical simulations. We also illustrate a method to calculate the cumulative geometric (Berry’s) phase. This work complements ongoing experimental efforts to detect a muon EDM at PSI and contributes to a broader understanding of spin-precession systematic effects.

Implementation of the frozen-spin technique for the search for a muon electric dipole moment

Applying the frozen-spin technique in a compact 3 T solenoid will enable a search for the muon electric dipole moment (EDM) with unprecedented sensitivity, improving upon the current direct limit by approximately a factor of 1000. After injection of a selected muon, a pulsed magnetic field will reduce its longitudinal momentum sufficiently to be confined within a static weakly-focusing magnetic field and maintain a closed circular orbit. A precisely tuned radial electric field will cancel the spin precession induced by the muon's anomalous magnetic moment, a = (g - 2)/2, relative to the orientation of the momentum. In this configuration, the EDM becomes the only remaining inherent source of relative precession. Asymmetry in the direction and energy of positrons emitted from muon decay provides an experimental signature of such precession.In the first of two phases, 28 MeV/c muons from the πE1 beamline at PSI will be used to demonstrate the systems necessary for injecting and trapping muons, tuning fields to the frozen-spin condition and reconstructing positron trajectories. Designs for the coils producing the pulsed magnetic field and the electrodes applying the frozen-spin electric field are currently being evaluated with simulations and prototypes. These systems must be designed in parallel, especially due to the impact of eddy-currents induced in the electrodes by the pulsed magnetic field. The electrode design must minimise eddy-currents to preserve the field strength of the pulsed field responsible for muon trapping, while maintaining the electric field uniformity necessary to achieve the sensitivity goal. This article summarises some of the efforts underway to address these design challenges.

Status of the search for a muon EDM using the frozen-spin technique

Despite the many successes of the Standard Model of particle physics, there are still several physical observations that it cannot explain, such as the matter-antimatter asymmetry, non-zero neutrino masses, and the microscopic nature of dark matter. To address these limitations, extensions to the standard model are necessary, and searches for electric dipole moments (EDMs) of leptons are valuable test. The search for a muon EDM is the only search on a bare lepton of the second generation, complementing the searches for an EDM of the electron using polar molecules. A non-zero EDM of the muon would indicate Charge-Parity symmetry violation beyond the standard model. A dedicated experimental search for the muon EDM is being set up at PSI using the frozen-spin technique. In this technique, the anomalous spin precession of the muons in a storage ring is suppressed by applying an electric field in the radial direction. The muon EDM experiment will take place in two phases: the first phase will demonstrate the frozen-spin technique using a precursor experiment with 28 MeV/c muons, while the second phase will make use of 125 MeV/c muons, which could search for the muon EDM with a sensitivity of 6 × 10-23 e·cm. In this talk, we describe the precursor experiment at PSI and provide an update on the status of the experiment.

Systematic effects in the search for a muon electric dipole moment using the frozen-spin technique

At the Paul Scherrer Institute we are developing a high precision instrument to measure the electric dipole moment (EDM) of the muon. The salient feature of the experiment is the use of the frozen-spin technique to suppress the anomalous precession of the muon spin, allowing for a sensitivity that cannot be achieved with conventional g-2 muon storage rings. With this technique, the expected statistical sensitivity for the EDM after one year of data taking is 6 × 10-23 e · cm with a p = 125 MeV/c muon beam available at PSI.Reaching this goal necessitates a comprehensive analysis on spurious effects that mimic the EDM signal. This work discusses a quantitative approach to study systematic effects for the frozen-spin technique when searching for the muon EDM with a focus on the kinematics of decay positrons in the context of this experiment, which operates at muon momenta well below the ultrarelativistic limit.

Hyperfine and P, T odd properties in BiO: comparison between coupled-cluster method and multi-reference perturbation method based on a Dirac Hamiltonian

Polar diatomic molecules are attractive in the search for the electron electric dipole moment (eEDM) and the scalar-pseudoscalar (S-PS) interaction, both of which violate time-reversal and parity symmetries. In this study, we examined the electronic ground state of BiO and evaluated the effective electric field (E eff) of eEDM and the W s coefficients of the S-PS interaction. BiO forms a complex chemical bond due to the open-shell configurations of Bi (6p) and O (2p). Consequently, we performed four-component relativistic calculations using complete-active-space second-order perturbation theory (CASPT2), as well as coupled-cluster singles and doubles (CCSD) and CCSD perturbative triples (CCSD(T)) methods. Our analysis revealed that BiO exhibited a multiconfigurational character, as the Hartree-Fock configuration accounted for only 68% of the reference wave function for CASPT2. Nevertheless, for the hyperfine coupling constant (A//), CCSD and CCSD(T) reproduced the experimental value better than CASPT2, indicating that CC methods can capture important excited configurations, rendering multireference treatment unnecessary. The deficiency of CASPT2 in reproducing A// could be attributed to the inadequate treatment of orbital relaxation effects. Our proposed values of E eff and W s for BiO (17 GV/cm and −36 kHz, respectively), derived at the CCSD level, were moderately large for the parity, time-odd experiment.

Atomic Comagnetometer with a Closed-Loop Optically Aligned 87 Rb Dual-Frequency Oscillator

Comagnetometers have been widely used in fundamental research, such as tests of spin-gravity coupling and searches for permanent electric dipole moments (EDMs). Here, we report a comagnetometer that consists of simultaneous closed-loop oscillation of the $F=1$ and $F=2$ hyperfine Zeeman transitions of optically aligned ${}^{87}$$\mathrm{Rb}$ atoms. The Allan deviation of the $F=2$ and $F=1$ oscillation-frequency ratio reaches $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ after running continuously for 2 days, corresponding to a sensitivity of approximately $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}\phantom{\rule{0.2em}{0ex}}\mathrm{eV}$ for the measurement of the hypothetical spin-dependent gravitational energy of the proton. The long-term stability of the comagnetometer can be further improved by system-level thermal control and optimization of the experimental parameters.

RETRACTED: Investigation of polarized proton spin coherence time at storage rings

The idea of the Electric Dipole Moment (EDM) search using the storage ring with polarized beam demands long Spin Coherence Time (SCT). It is the time during which the RMS spread of the orientation of spins of all particles in the bunch reaches one radian. Long SCT is needed to observe a coherent effect on polarization induced by the EDM. The possibility of getting a 1000 s SCT for deuterons has been shown experimentally at COoler SYnchrotron (COSY), accelerator at FZJ Jülich, Germany. Reaching high values of SCT for protons is more challenging due to a higher anomalous magnetic moment. Obtaining sufficient proton SCT is obligatory for planned EDM search experiments at COSY and the ProtoType EDM Ring (PTR). It has been shown that the second order momentum compaction factor (α 1) has to be optimized along with chromaticities (ξx, y ) to get high SCT. Three families of sextupoles have to be used. The optimal values of chromaticities and α 1 are discussed. The racetrack option of PTR is investigated.

Electric dipole moment of charged particles using storage rings

The Standard Model (SM) of Particle Physics cannot explain the matter-antimatter asymmetry in the Universe. Especially, new sources of CP-violation are necessary, and this is why physics beyond the SM is being explored. The search for permanent Electric Dipole Moments (EDMs) of elementary particles has the potential to provide a powerful tool to discover new sources of CP-violation. Finding an EDM would be a convincing indication for physics beyond the SM. Moreover, a rotating polarized beam used in EDM searches is sensitive to oscillating EDM caused by axions or axion-like particles (ALPs), the candidates for the dark matter. Storage rings are promising devices to measure EDMs of charged particles by observing the effect of the EDM on the spin motion in the ring. The Cooler Synchrotron COSY at the Forschungszentrum Jülich provides polarized protons and deuterons with momenta up to 3.7 GeV/c and it constitutes an suitable testing ground and starting point for an experimental program to search for EDMs of charged particles. This report provides an overview of the current status of the JEDI project for the first direct measurement of the deuteron EDM at COSY. The analysis is currently ongoing. Due to the complexity of storage rings, this study combines high precision measurements and thorough understanding of the systematic uncertainties involved.

Systematic effects in the search for the muon electric dipole moment using the frozen-spin technique

At the Paul Scherrer Institute (PSI) we are developing a high precision instrument to measure the muon electric dipole moment (EDM). The experiment is based on the frozen-spin method in which the spin precession induced by the anomalous magnetic moment is suppressed, thus increasing the signal-to-noise ratio for EDM signals to achieve a sensitivity otherwise unattainable using conventional g - 2 muon storage rings. The expected statistical sensitivity for the EDM after a year of data taking is 6 10−23e cm with the p = 125 MeV/c muon beam available at the PSI. Reaching this goal necessitates a comprehensive analysis on spurious effects that mimic the EDM signal. This work discusses a quantitative approach to study systematic effects for the frozen-spin method when searching for the muon EDM. Equations for the motion of the muon spin in the electromagnetic fields of the experimental system are analytically derived and validated by simulation.

Estimated performance of the TRIUMF ultracold neutron source and electric dipole moment apparatus

Searches for the permanent electric dipole moment of the neutron (nEDM) provide strong constraints on theories beyond the Standard Model of particle physics. The TUCAN collaboration is constructing a source for ultra-cold neutrons (UCN) and an apparatus to search for the nEDM at TRIUMF, Vancouver, Canada. In this work, we estimate that the spallation-driven UCN source based on a superfluid helium converter will provide (1.38 ± 0.02) 107 polarized UCN at a density of 217 ± 3 UCN/cm3 to a room-temperature EDM experiment per fill. With (1.43 ± 0.02) 106 neutrons detected after the Ramsey cycle, the statistical sensitivity for an nEDM search per storage cycle will be (1.94 ± 0.06) × 10−25 ecm (1σ). The goal sensitivity of 10−27 ecm (1σ) can be reached within 281 ± 16 measurement days.

Perspectives on electric dipole moments of atoms and molecules

Searches for a permanent electric dipole moment (EDM) of a fundamental particle started with the key idea by Ramsey and Purcell of exploitation of discrete symmetries, such as parity, more than seven decades ago. These searches provide a model-independent test of theoretical frameworks, in particular, the Standard Model of particle physics. Over time, a large number of experimentally suitable systems, also atoms and molecules, provided more stringent limits on possible EDMs. We discuss some perspectives on such experiments in the context of statistics, systematics, and sensitivities to beyond the Standard Model physics.

SiPM module for the ACME III electron EDM search

This report shows the design and performance of a large area Silicon Photomultiplier (SiPM) module developed for the detection of fluorescent light emitted from a ∼1 liter scale volume. The module was optimized for the planned ACME III electron electric dipole moment (eEDM) search, which will be a ∼10 TeV probe for the existence of physics beyond the Standard Model of particle physics. The ACME experiment searched for the eEDM with the world’s highest sensitivity using cold ThO polar molecules (ACME II (Andreev et al., 2018 )). In ACME III, SiPMs will be used for detection of fluorescent photons (the fundamental signal of the experiment) instead of PMTs, which were used in the previous measurement. We have developed an optimized SiPM module, based on a 16-channel SiPM array. Key operational parameters are characterized, including gain and noise. The SiPM dark count rate, background light sensitivity, and optical crosstalk are found to all be well suppressed and more than sufficient for the ACME III application.

Magnetic field mapping of inaccessible regions using physics-informed neural networks

A difficult problem concerns the determination of magnetic field components within an experimentally inaccessible region when direct field measurements are not feasible. In this paper, we propose a new method of accessing magnetic field components using non-disruptive magnetic field measurements on a surface enclosing the experimental region. Magnetic field components in the experimental region are predicted by solving a set of partial differential equations (Ampere’s law and Gauss’ law for magnetism) numerically with the aid of physics-informed neural networks (PINNs). Prediction errors due to noisy magnetic field measurements and small number of magnetic field measurements are regularized by the physics information term in the loss function. We benchmark our model by comparing it with an older method. The new method we present will be of broad interest to experiments requiring precise determination of magnetic field components, such as searches for the neutron electric dipole moment.

CP-violating axion interactions in effective field theory

Axions are introduced to explain the observed smallness of the overline{theta} term of QCD. Standard Model extensions typically contain new sources of CP violation, for instance to account for the baryon asymmetry of the universe. In the presence of additional CP-violating sources a Peccei-Quinn mechanism does not remove all CP violation, leading to CP-odd interactions among axions and Standard Model fields. In this work, we use effective field theory to parametrize generic sources of beyond-the-Standard-Model CP violation. We systematically compute the resulting CP-odd couplings of axions to leptons and hadrons by using chiral perturbation theory. We discuss in detail the phenomenology of the CP-odd axion couplings and compare limits from axion searches, such as fifth force and monopole-dipole searches and astrophysics, to direct limits on the CP-violating operators from electric dipole moment experiments. While limits from electric dipole moment searches are tight, the proposed ARIADNE experiment can potentially improve the existing constraints in a window of axion masses.

Sensitivity of the YbOH molecule to PT -odd effects in an external electric field

An electron electric dipole moment (eEDM) search using laser-coolable triatomics such as YbOH is one of the most sensitive probes for physics beyond the standard model. The eEDM-induced energy shift is proportional to the polarization ($P$) of the molecule. Similarly to diatomics with an $\mathrm{\ensuremath{\Omega}}$-doubling structure, it was assumed that for triatomics with an $l$-doubling structure, related to the vibrational angular momentum, $P$ can be easily saturated to almost 100% with a moderate external electric field. We developed a method for the calculation of the properties of triatomic molecules and applied it to a calculation of $P$ of $^{174}\mathrm{YbOH}$ in the first excited $v=1$ bending mode. Calculations showed that most of the levels reach less than 50% efficiency. We showed that this fact is related to the Hund's case $b$ coupling scheme of YbOH. As the coupling scheme (for $\mathrm{\ensuremath{\Omega}}=1/2$ molecules) approaches the $a$ (or $c$) case, polarization increases up to 100%. The results of our calculations should be used for the correct extracting of the eEDM value from YbOH experiments and similar calculations are required for other molecules.

Muon electric dipole moment as a probe of flavor-diagonal CP violation

Electric dipole moments (EDMs) of elementary particles are powerful probes of new physics with flavor-diagonal CP violation. The reported discrepancy in the muon anomalous magnetic moment motivates us to explore to what extent new physics with flavor-diagonal CP violation to address the discrepancy is probed by searches for the muon EDM. As a benchmark, we focus on a CP-violating two-Higgs-doublet model to explain the muon g−2 anomaly where the muon exclusively couples to one Higgs doublet. Since contributions to flavor violating processes as well as the electron EDM are suppressed, the muon EDM becomes an essential probe of the model. Our result shows that some viable parameter space leads to the muon EDM of around dμ≃6×10−23e cm probed by the PSI experiment and most of the parameter space is covered by the proposed J-PARC experiment.

Development of a Laser Frequency Stabilization and an Optical Transmission System for the Francium Electric Dipole Moment Search

Abstract We developed a laser frequency stabilization and an optical fiber transmission system for the the francium electric dipole moment search. The absolute accuracy of a laser frequency stabilization scheme using a state-of-the-art commercial wavelength meter was 0.48 MHz at ±2 nm and -1.33 MHz at ±200 nm from calibration wavelength, respectively, and the frequency instability is below 10-9 with a standard deviation of 0.56 MHz over 60 hours. We also demonstrated that a 400 m long fiber laid between laboratories can transmit 30 mW of trapping laser light, which is sufficient for a magneto-optical trapping of francium. The polarization crosstalk in the fiber was stable at -25 dB over 12 hours of measurement.