Search For Electric Dipole Moment Research Articles

Search for electric dipole moments in storage rings

The JEDI collaboration aims at making use of storage ring to provide the most precise measurement of the electric dipole moments of hadrons. The method makes exploits a longitudinal polarized beam. The existence an electric dipole moment would generate a torque slowly twisting the particle spin out of plan of the storage ring into the vertical direction. The observation of non zero electric dipole moment would represent a clear sign of new physics beyond the Standard Model. Feasiblity tests are presently undergoing at the COSY storage ring Forschungszentrum Julich (Germany), to develop the novel techniques to be implemented in a future dedicated storage ring.

Recent Results and Progress on Leptonic and Storage Ring EDM Searches

The Standard Model is incomplete and unable to explain the matter-antimatter asymmetry in the universe. Many extensions of the Standard Model predict new particles and interactions with additional [Formula: see text]-violating phases that can explain this imbalance. Electric dipole moments (EDMs) of fundamental particles, which are generated by [Formula: see text]-violating interactions, can be enhanced by many orders of magnitude by contributions from this new physics to a magnitude within reach of current and planned experiments. New approaches to EDM searches using storage rings, and their sensitivity to new physics are presented.

Studies of Systematic Limitations in the EDM Searches at Storage Rings

Searches of the electric dipole moment (EDM) at a pure magnetic ring, like COSY, encounter strong background coming from magnetic dipole moment (MDM). The most troubling issue is the MDM spin rotation in the so-called imperfection, radial and longitudinal, B-fields. To study the systematic effects of the imperfection fields at COSY we proposed the original method which makes use of the two static solenoids acting as artificial imperfections. Perturbation of the spin tune caused by the spin kicks in the solenoids probes the systematic effect of cumulative spin rotation in the imperfection fields all over the ring. The spin tune is one of the most precise quantities measured presently at COSY at [Formula: see text] level. The method has been successfully tested in September 2014 run at COSY, unravelling strength of spin kicks in the ring’s imperfection fields at the level of [Formula: see text].

Polarimetry for Stored Polarized Hadron Beams

Feasibility studies using 0.97-GeV/c polarized deuterons to determine the suitability of storage rings in the search for intrinsic electric dipole moments have led to new developments in storage ring polarimeters. Efficiency has increased with the use of thick carbon targets. The calibration of the effects of geometric and rate-dependent errors has made possible the subtraction of these systematic errors, resulting in sensitivities at or below 10[Formula: see text] to polarization changes during the time of the store. Tagging polarimeter events with the clock time had made available the turn number for each event, making possible longitudinal profile and horizontal polarization measurements. These have been used to explore the correction of second-order contributions to decoherence using sextupole fields, yielding horizontal polarization lifetimes as long as 20 minutes. Such studies may be extended to protons and 3He.

Storage Ring Based EDM Search — Achievements and Goals

This paper summarizes the experimental achievements of the JEDI (Jülich Electric Dipole moment Investigations) Collaboration to exploit and demonstrate the feasibility of charged particle Electric Dipole Moment searches with storage rings at the Cooler Synchrotron COSY of the Forschungszentrum Jülich. Recent experimental results, design and optimization of critical accelerator elements, progress in beam and spin tracking, and future goals of the R & D program at COSY are presented.

Geometric phases in electric dipole searches with trapped spin-1/2 particles in general fields and measurement cells of arbitrary shape with smooth or rough walls

The important role of geometric phases in searches for a permanent electric dipole moment of the neutron, using Ramsey separated oscillatory field nuclear magnetic resonance, was first noted by Commins and investigated in detail by Pendlebury et al. Their analysis was based on the Bloch equations. In subsequent work using the spin density matrix Lamoreaux and Golub showed the relation between the frequency shifts and the correlation functions of the fields seen by trapped particles in general fields (Redfield theory). More recently we presented a solution of the Schr\"odinger equation for spin-$1/2$ particles in circular cylindrical traps with smooth walls and exposed to arbitrary fields [Steyerl et al.] Here we extend this work to show how the Redfield theory follows directly from the Schr\"odinger equation solution. This serves to highlight the conditions of validity of the Redfield theory, a subject of considerable discussion in the literature [e.g., Nicholas et al.] Our results can be applied where the Redfield result no longer holds, such as observation times on the order of or shorter than the correlation time and non-stochastic systems and thus we can illustrate the transient spin dynamics, i.e. the gradual development of the shift with increasing time subsequent to the start of the free precession. We consider systems with rough, diffuse reflecting walls, cylindrical trap geometry with arbitrary cross section, and field perturbations that do not, in the frame of the moving particles, average to zero in time. We show by direct, detailed, calculation the agreement of the results from the Schr\"odinger equation with the Redfield theory for the cases of a rectangular cell with specular walls and of a circular cell with diffuse reflecting walls.

New search for the neutron electric dipole moment with ultracold neutrons at ILL

The search for an electric dipole moment (EDM) of the neutron is a crucial test for theoretical particle physics models with violation of time and spatial invariance. A new experiment recently has been carried out at the High-Flux Reactor at Institut Laue-Langevin, using the upgraded double-chamber magnetic resonance spectrometer developed at Petersburg Nuclear Physics Institute. The result is interpreted as an upper limit on the value of the neutron EDM, $|{d}_{n}|l5.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}26}{e}_{}\phantom{\rule{4pt}{0ex}}\mathrm{cm}$ (90% C.L.). This article provides a detailed description of the setup and experimental procedures, along with a discussion of possibilities for further improvement of the experimental accuracy.

Colliding or co-rotating ion beams in storage rings for EDM search

A new approach to search for and measure the electric dipole moment (EDM) of the proton, deuteron and some other light nuclei is presented. The idea of the method is to store two ion beams, circulating with different velocities, in a storage ring with crossed electric and magnetic guiding fields. One beam is polarized and its EDM is measured using the so-called ‘frozen spin’ method. The second beam, which is unpolarized, is used as a co-magnetometer, sensitive to the radial component of the ring’s magnetic field. The particle’s magnetic dipole moment (MDM) couples to the radial magnetic field and mimics the EDM signal. Measuring the relative vertical orbit separation of the two beams, caused by the presence of the radial magnetic field, one can control the unwanted MDM spin precession. Examples of the parameters for EDM storage rings for protons and other species of ions are presented. The use of crossed electric and magnetic fields helps to reduce the size of the ring by a factor of 10–20. We show that the bending radius of such an EDM storage ring could be about 2–3 m. Finally, a new method of increasing the spin coherence time, the so-called ‘spin wheel’, is proposed and its applicability to the EDM search is discussed.

Low‐energy precision tests of the standard model: a snapshot

This brief review describes a class of uniquely crafted particle physics experiments that typically each tackle just one investigation—and they do that very well. The aim of these experiments is to both establish Standard Model parameters and also to provide unique tests in search of new physics. I provide a brief snapshot of many of the current activities, selected with a bias toward low‐energy and high precision. These include searches for permanent electric dipole moments, charged lepton flavor violation, tests of the weak interaction, and other broad searches for deviations from very precise Standard Model predictions, such as the muon's anomalous magnetic moment. I highlight what drives these efforts and how they might impact a new Standard Model. image

Ac Stark effect in ThOH3Δ1for the electron electric-dipole-moment search

A method and code for calculations of diatomic molecules in the external variable electromagnetic field have been developed. Code applied for calculation of systematics in the electron's electric dipole moment search experiment on ThO $H^3\Delta_1$ state related to geometric phases, including dependence on $\Omega$-doublet, rotational level, and external static electric field. It is found that systematics decrease cubically with respect to the frequency of the rotating transverse component of the electric field. Calculation confirms that experiment on ThO $H^3\Delta_1$ state is very robust against systematic errors related to geometric phases.

New experimental limit on the electric dipole moment of the electron in a paramagnetic insulator

We report results of an experimental search for the intrinsic Electric Dipole Moment (EDM) of the electron using a solid-state technique. The experiment employs a paramagnetic, insulating gadolinium gallium garnet (GGG) that has a large magnetic response at low temperatures. The presence of the eEDM would lead to a small but non-zero magnetization as the GGG sample is subject to a strong electric field. We search for the resulting Stark-induced magnetization with a sensitive magnetometer. Recent progress on the suppression of several sources of background allows the experiment to run free of spurious signals at the level of the statistical uncertainties. We report our first limit on the eEDM of $(-5.57 \pm 7.98 \pm 0.12)\times$10$^{-25}$e$\cdot$cm with 5 days of data averaging.

Mercury monohalides: suitability for electron electric dipole moment searches.

Heavy polar diatomic molecules are the primary tools for searching for the T-violating permanent electric dipole moment of the electron (eEDM). Valence electrons in some molecules experience extremely large effective electric fields due to relativistic interactions. These large effective electric fields are crucial to the success of polar-molecule-based eEDM search experiments. Here we report on the results of relativistic abinitio calculations of the effective electric fields in a series of molecules that are highly sensitive to an eEDM, the mercury monohalides (HgF, HgCl, HgBr, and HgI). We study the influence of the halide anions on E_{eff}, and identify HgBr and HgI as attractive candidates for future electric dipole moment search experiments.

Electric dipole moments: A global analysis

We perform a global analysis of searches for the permanent electric dipole moments (EDMs) of the neutron, neutral atoms, and molecules in terms of six leptonic, semileptonic, and nonleptonic interactions involving photons, electrons, pions, and nucleons. Translating the results into fundamental CP-violating effective interactions through dimension six involving Standard Model particles, we obtain rough lower bounds on the scale of beyond the Standard Model CP-violating interactions ranging from 1.5 TeV for the electron EDM to 1300 TeV for the nuclear spin-independent electron-quark interaction. We show that future measurements involving systems or combinations of systems with complementary sensitivities to the low-energy parameters may extend the mass reach by an order of magnitude or more.

Theoretical study of thorium monoxide for the electron electric dipole moment search: Electronic properties of H3Δ1 in ThO

Recently, improved limits on the electron electric dipole moment, and dimensionless constant, kT,P, characterizing the strength of the T,P-odd pseudoscalar–scalar electron–nucleus neutral current interaction in the H3Δ1 state of ThO molecule were obtained by the ACME collaboration [J. Baron et al., Science 343, 269 (2014)]. The interpretation of the experiment in terms of these fundamental quantities is based on the results of theoretical study of appropriate ThO characteristics, the effective electric field acting on electron, Eeff, and a parameter of the T,P-odd pseudoscalar–scalar interaction, WT,P, given in Skripnikov et al. [J. Chem. Phys. 139, 221103 (2013)] by St. Petersburg group. To reduce the uncertainties of the given limits, we report improved calculations of the molecular state–specific quantities Eeff, 81.5 GV/cm, and WT,P, 112 kHz, with the uncertainty within 7% of the magnitudes. Thus, the values recommended to use for the upper limits of the quantities are 75.8 GV/cm and 104 kHz, correspondingly. The hyperfine structure constant, molecule-frame dipole moment of the H3Δ1 state, and the H3Δ1 → X1Σ+ transition energy which, in general, can serve as a measure of reliability of the obtained Eeff and WT,P values are also calculated. In addition, we report the first calculation of g-factor for the H3Δ1 state of ThO. The results are compared to the earlier experimental and theoretical studies, and a detailed analysis of uncertainties of the calculations is given.

EDM measurement in 129Xe atom using dual active feedback nuclear spin maser

The technique of an active nuclear spin maser is adopted in the search for electric dipole moment in a diamagnetic atom 129Xe. In order to reduce systematic uncertainties arising from long-term drifts of the external magnetic field and from the contact interaction between longitudinal polarized Rb atoms and 129Xe spin, a 3He comagnetometer with a double-cell geometry was employed. The remaining shift, which turned out to show some correlation with the cell temperature, was mitigated by stabilizing the cell temperature. As a result, the frequency drift of the 129Xe maser was reduced from 12 mHz to 700 μHz, and the determination precision of frequency of 8.7 nHz was obtained for a 2×104 s measurement time using the double-cell geometry cell.

Experimental search for the electron electric dipole moment with laser cooled francium atoms

A laser cooled heavy atom is one of the candidates to search for the permanent electric dipole moment (EDM) of the electron due to the enhancement mechanism and its long coherence time. The laser cooled francium (Fr) factory has been constructed to perform the electron EDM search at the Cyclotron and Radioisotope Center, Tohoku University. The present status of Fr production and the EDM measurement system is presented.

A proposed method of efficient laser trapping of neutral radium atoms

We report theoretical studies of an efficient accumulation of 225Ra atoms in a magneto-optical trap (MOT) from an atomic beam. The number of atoms in the trap is limited due to the large leakage into metastable D states from the cooling transition and the loss mechanism from collisions with the background gases and with other elements in the atomic beam. We propose a setup consisting of an efficient Zeeman slower, an optical atomic beam deflector, and an Egg-MOT, which provides a large capture velocity, e.g. the Zeeman slower capture velocity of 581 ms−1 and the MOT capture velocity of 46 ms−1. Furthermore, the pure slow atomic beam produced by the optical atomic beam deflector can maximize the number of trapped atoms and their lifetime in a ultra high vacuum chamber by minimizing the collisional loss. Our proposed setup allows for the search for a permanent electric dipole moment based on laser-cooled and trapped radium atoms with improved sensitivity.

Alkali-vapor magnetic resonance driven by fictitious radiofrequency fields

We demonstrate an all-optical 133Cs scalar magnetometer, operating in nonzero magnetic field, in which the magnetic resonance is driven by an effective oscillating magnetic field provided by the AC Stark shift of an intensity-modulated laser beam. We achieve a projected shot-noise-limited sensitivity of 1.7fT/Hz and measure a technical noise floor of 40fT/Hz. These results are essentially identical to a coil-driven scalar magnetometer using the same setup. This all-optical scheme offers advantages over traditional coil-driven magnetometers for use in arrays and in magnetically sensitive fundamental physics experiments, e.g., searches for a permanent electric dipole moment of the neutron.

StrongPinvariance, neutron electric dipole moment, and minimal left-right parity at LHC

In the minimal left-right model the choice of left-right symmetry is twofold: either generalized parity $\mathcal{P}$ or charge conjugation $\mathcal{C}$. In the minimal model with spontaneously broken strict $\mathcal{P}$, a large tree-level contribution to strong $CP$ violation can be computed in terms of the spontaneous phase $\ensuremath{\alpha}$. Searches for the neutron electric dipole moments then constrain the size of $\ensuremath{\alpha}$. Following the latest update on indirect $CP$ violation in the kaon sector, a bound on ${W}_{R}$ mass at 20 TeV is set. Possible ways out of this bound require a further hypothesis, either a relaxation mechanism or explicit breaking of $\mathcal{P}$. To this end, the chiral loop of the neutron electric dipole moment at next-to-leading order is recomputed and provides an estimate of the weak contribution. Combining this constraint with other $CP$-violating observables in the kaon sector allows for ${M}_{{W}_{R}}\ensuremath{\gtrsim}3\text{ }\text{ }\mathrm{TeV}$. On the other hand, $\mathcal{C}$ symmetry is free from such constraints, leaving the right-handed scale within the experimental reach.

Absolute frequency measurement of the7s2 1S0–7s7p 1P1transition inRa225

Transition frequencies were determined for transitions in Ra in an atomic beam and for reference lines in Te$_2$ molecules in a vapor cell. The absolute frequencies were calibrated against a GPS stabilized Rb-clock by means of an optical frequency comb. The 7s$^2\,^1$S$_0$(F = 1/2)-7s7p$\,^1$P$_1$(F = 3/2) transition in $^{225}$Ra was determined to be $621\,042\,124(2)\,$MHz. The measurements provide input for designing efficient and robust laser cooling of Ra atoms in preparation of a search for a permanent electric dipole moment in Ra isotopes.