Dipole Moment Measurements Research Articles

Development of francium atomic beam for the search of the electron electric dipole moment

For the measurement of the electron electric dipole moment using Fr atoms, a Fr ion-atom conversion is one of the most critical process. An ion-atom converter based on the orthotropic type of Fr source has been developed. This converter is able to convert a few keV Fr ion beam to a thermal atomic beam using a cycle of the surface ionization and neutralization. In this article, the development of the converter is reported.

Stochastic multi-channel lock-in detection

High-precision measurements benefit from lock-in detection of small signals. Here we discuss the extension of lock-in detection to many channels, using mutually orthogonal modulation waveforms, and show how the choice of waveforms affects the information content of the signal. We also consider how well the detection scheme rejects noise, both random and correlated. We address the particular difficulty of rejecting a background drift that makes a reproducible offset in the output signal and we show how a systematic error can be avoided by changing the waveforms between runs and averaging over many runs. These advances made possible a recent measurement of the electron's electric dipole moment (Hudson et al 2011 Nature 473 493).

Infrastructure for Next Generation Experiments with Ultracold Neutrons

Abstract Next-generation experiments with ultracold neutrons are driven by the strength of the neutron sources as well as by the environmental conditions where the experiments are performed. Properly designed beam position infrastructure is therefore crucial to make use of new facilities, e.g. for the measurement of the electric dipole moment of the neutron. As an example for a next-generation effort, the beam position requirements at the FRM-II are discussed and the progress of the implementation of the non-magnetic facility is 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.

Measurement and modeling of thermal flow in an enclosed tube containing superfluid helium film

We describe measurements of the thermal conductivity of a vertical tube partially filled with superfluid liquid helium at saturated vapor pressure. The tube was heated from the top while the bottom was maintained at 0.3K. Thermal conduction through superfluid film creep and vapor reflux has been modeled in the literature and previously measured at T⩾0.9K. From our measurements we assess the validity of the model at the lower temperatures, where significant temperature gradients develop, and consider the effect of ancillary thermal conductances. The work is motivated by the cryogenic requirements for a proposed cryogenic measurement of the electric dipole moment of the neutron.

Molecular interaction studies in hydrogen bonded polar binary mixtures

The molecular interactions between the polar systems of propan-1-ol (1PN) with alkyl benzoates (methyl benzoate and ethyl benzoate) for various mole fractions at different temperatures are studied by determining the dielectric permittivity in radio, microwave and optic frequency regions, respectively. Dipole moment, excess dipole moment, excess Helmholtz free energy, excess permittivity, relaxation time, excess inverse relaxation time and excess thermodynamical values are calculated using experimental data. Hamiltonian quantum mechanical calculations are performed on both pure and equimolar binary systems of 1PN with alkyl benzoates for the measurement of dipole moment from the ab initio Hartree–Fock and density functional theory (B3LYP) methods with 6-31 + G* and 6-311 + G** basis sets using Spartan 08 modelling software and these theoretical values are in good agreement with the experimental values.

Creation of polarized ultracold neutrons and observation of Ramsey resonance for electric dipole moment measurement

Polarized UCNs have been created by selecting only one spin state passing through a magnetized Fe foil. Typical degree of polarization was about 90 %. The polarization relaxation time in the prototype Ramsey cell was \(T_1 =1100^{+800}_{-400}\) s. Clear Ramsey resonance spectra have been observed for two precession time settings, tc = 100 ms and 30 s. The transverse relaxation time T2 was about 50 s.

Measurement of permanent electric dipole moments of charged hadrons in storage rings

Permanent Electric Dipole Moments (EDMs) of elementary particles violate two fundamental symmetries: time reversal invariance ( $\mathcal{T}$ ) and parity ( $\mathcal{P}$ ). Assuming the $\mathcal{CPT}$ theorem this implies $\mathcal{CP}$ violation. The $\mathcal{CP}$ violation of the Standard Model is orders of magnitude too small to be observed experimentally in EDMs in the foreseeable future. It is also way too small to explain the asymmetry in abundance of matter and anti-matter in our universe. Hence, other mechanisms of $\mathcal{CP}$ violation outside the realm of the Standard Model are searched for and could result in measurable EDMs. Up to now most of the EDM measurements were done with neutral particles. With new techniques it is now possible to perform dedicated EDM experiments with charged hadrons at storage rings where polarized particles are exposed to an electric field. If an EDM exists the spin vector will experience a torque resulting in change of the original spin direction which can be determined with the help of a polarimeter. Although the principle of the measurement is simple, the smallness of the expected effect makes this a challenging experiment requiring new developments in various experimental areas. Complementary efforts to measure EDMs of proton, deuteron and light nuclei are pursued at Brookhaven National Laboratory and at Forschungszentrum Jülich with an ultimate goal to reach a sensitivity of 10 − 29 e·cm.

Magnetic and dielectric properties of multiferroic Eu0.5Ba0.25Sr0.25TiO3 ceramics

Dielectric and magnetic properties of Eu0.5Ba0.25Sr0.25TiO3 are investigated between 10 and 300 K in the frequency range 10 Hz–100 THz. A peak in permittivity revealed near 130 K and observed ferroelectric hysteresis loops prove the ferroelectric order below this temperature. The peak in permittivity is given mainly by softening of the lowest frequency polar phonon (soft mode revealed in THz and infrared (IR) spectra) that demonstrates displacive character of the phase transition. Room-temperature X-ray diffraction analysis reveals cubic structure, but the IR reflectivity spectra give evidence of a lower crystal structure, presumably tetragonal I4/mcm with tilted oxygen octahedra as it has been observed in EuTiO3. The magnetic measurements show that the antiferromagnetic order occurs below 1.8 K. Eu0.5Ba0.25Sr0.25TiO3 has three times lower coercive field than Eu0.5Ba0.5TiO3; therefore, we propose this system for measurements of electric dipole moment of electron.

Parity- and time-reversal-violating moments of light nuclei

I present the calculation of parity- and time-reversal-violating moments of the nucleon and light nuclei, originating from the QCD $\bar \theta$ term and effective dimension-six operators. By applying chiral effective field theory these calculations are performed in a unified framework. I argue that measurements of a few light-nuclear electric dipole moments would shed light on the mechanism of parity and time-reversal violation.

Discover potential in a search for time-reversal invariance violation in nuclei

Time reversal invariance violating (TRIV) effects in low energy physics could be very important in searching for new physics, being complementary to neutron and atomic electric dipole moment (EDM) measurements. In this relation, we discuss a sensitivity of some TRIV observables to different models of time-reversal (CP) violation and their dependencies on nuclear structure. As a measure of a sensitivity of TRIV effects to the value of TRIV nucleon coupling constant, we introduce a coefficient of a “discovery potential”, which shows a possible factor for improving the current limits of the EDM experiments by measuring nuclear TRIV effects.

Advanced cold molecule electron EDM

Measurement of a non-zero electric dipole moment (EDM) of the electron within a few orders of magnitude of the current best limit of |d_e| < 1.05 e -27 e cm would be an indication of physics beyond the Standard Model. The ACME Collaboration is searching for an electron EDM by performing a precision measurement of electron spin precession in the metastable H state of thorium monoxide (ThO) using a slow, cryogenic beam. We discuss the current status of the experiment. Based on a data set acquired from 14 hours of running time over a period of 2 days, we have achieved a 1-sigma statistical uncertainty of 1 e -28 e cm/T^(1/2), where T is the running time in days.

Using high resolution electronic spectroscopy to probe the effects of ring twist on charge transfer in 2-phenylindole and N-phenylcarbazole

High resolution electronic spectra of 2-phenylindole (PI) and N-phenylcarbazole (PC) have been recorded in the collision-free environment of a molecular beam. Inertial defects determined from fits of the spectra were used to determine the twist angles between the two chromophores and their attached benzene rings in the ground (S0) and excited (S1) electronic states. PI was found to be significantly more planar than PC, especially in the S1 state. Stark-effect measurements of the permanent electric dipole moments of both molecules in both states show that significantly more charge is transferred from the phenyl group to the chromophore in PI (0.13e) than in PC (0.076e) when the photon is absorbed. Thereby demonstrated for the first time is a direct connection between photo-induced geometry change and charge transfer on excitation of an isolated molecule by light.

Quantum Dynamics in Atomic-Fountain Experiments for Measuring the Electric Dipole Moment of the Electron with Improved Sensitivity

An improved measurement of the electron electric dipole moment (EDM) appears feasible using ground-state alkali atoms in an atomic fountain in which a strong electric field, which couples to a conceivable electron dipole moment (EDM), is applied perpendicular to the fountain axis. In a practical fountain, the ratio of the atomic tensor Stark shift to the Zeeman shift is a facto mu~100. We expand the complete time evolution operator in inverse powers of this ratio; complete results are presented for atoms of total spin F=3, 4, and 5. For a specific set of entangled hyperfine sublevels (coherent states), potential systematic errors enter only as even powers of 1/mu, making the expansion rapidly convergent. The remaining EDM mimicking effects are further suppressed in a proposed double-differential setup, where the final state is interrogated in a differential laser configuration, and the direction of the strong electric field also is inverted. Estimates of the signal available at existing accelerator facilities indicate that the proposed apparatus offers the potential for a drastic improvement in EDM limits over existing measurements, and for constraining the parameter space of supersymmetric (SUSY) extensions of the Standard Model.

Validation of a triangular quantum well model for GaN-based HEMTs used in pH and dipole moment sensing

Gallium nitride (GaN) is a relatively new semiconductor material that has the potential of replacing gallium arsenide (GaAs) in some of the more recent technological applications, for example chemical sensor applications. In this paper, we introduce a triangular quantum well model for an undoped AlGaN/GaN high electron mobility transistor (HEMT) structure used as a chemical and biological sensor for pH and dipole moment measurements of polar liquids. We have performed theoretical calculations related to the HEMT characteristics and we have compared them with experimental measurements carried out in many previous papers. These calculations include the current–voltage (I–V) characteristics of the device, the surface potential, the change in the drain current with the dipole moment and the drain current as a function of pH. The results exhibit good agreement with experimental measurements for different polar liquids and electrolyte solutions. It is also found that the drain current of the device exhibits a large linear variation with the dipole moment, and that the surface potential and the drain current depend strongly on the pH. Therefore, it can distinguish molecules with slightly different dipole moments and solutions with small variations in pH. The ability of the device to sense biomolecules (such as proteins) with very large dipole moments is investigated.

Measurement of the electron's electric dipole moment using YbF molecules: methods and data analysis

We recently reported a new measurement of the electron's electric dipole moment using YbF molecules (Hudson et al 2011 Nature473 493). Here, we give a more detailed description of the methods used to make this measurement, along with a fuller analysis of the data. We show how our methods isolate the electric dipole moment from imperfections in the experiment that might mimic it. We describe the systematic errors that we discovered, and the small corrections that we made to account for these. By making a set of additional measurements with greatly exaggerated experimental imperfections, we find upper bounds on possible uncorrected systematic errors which we use to determine the systematic uncertainty in the measurement. We also calculate the size of some systematic effects that have been important in previous electric dipole moment measurements, such as the motional magnetic field effect and the geometric phase, and show them to be negligibly small in the present experiment. Our result is consistent with an electric dipole moment of zero, so we provide upper bounds to its size at various confidence levels. Finally, we review the prospects for future improvements in the precision of the experiment.

Excess Dielectric and Thermodynamical Studies on Hydrogen Bonded Binary Mixtures of Propan-1-ol with Methyl and Ethyl Benzoates

The molecular interactions between the polar systems propan-1-ol with alkyl benzoates (methyl benzoate and ethyl benzoate) for various mole fractions at different temperatures were studied by determining the dielectric permittivity using - LF impedance analyzer, microwave bench and Abbe's refractometer in radio, microwave and optic frequency regions respectively. Dipole moment, excess dipole moment, excess Helmholtz free energy, excess permittivity, relaxation time, excess inverse relaxation time and excess thermodynamical values are calculated using experimental data. Hamiltonian quantum mechanical calculations are performed on both pure and equimolar binary systems of propan-1-ol with alkyl benzoates for the measurement of dipole moment using PC Spartan and Argus lab Modeling softwares and these theoretical values are in good agreement with the experimental values. These studies can give information on its structure and interaction.

Demonstration of focusing by a neutron accelerator

Space-time focusing was demonstrated by a neutron accelerator. Test experiments were performed by using very slow neutrons at High-Flux Reactor at Institut Laue-Langevin. Focusing of neutrons at the detector position through the accelerator was observed. Focusing neutrons enables us to transport the neutrons while maintaining density from source to experimental position. This will be a powerful technique for measurement of the permanent electric dipole moment of neutrons, which require a high density of neutrons.

Spin rotation by Earthʼs gravitational field in a “frozen-spin” ring

Detailed calculations of spin rotation by the Earthʼs gravitational field in a frozen-spin ring are presented in three different coordinate systems and used (a) to show that the systematic error caused by gravitation in a proposed electric dipole moment measurement can be unambiguously determined, and (b) to propose measuring the spin-gravity effect in a dedicated frozen-spin ring using electrons.

Broadband velocity modulation spectroscopy of HfF+: Towards a measurement of the electron electric dipole moment

Precision spectroscopy of trapped HfF+ will be used to search for the permanent electric dipole moment of the electron (eEDM). Prior to this study, spectroscopic information necessary for state preparation, readout, and analysis of systematic errors was not available. We have developed a powerful technique for broadband, high-resolution survey spectroscopy of molecular ions that combines cavity-enhanced direct frequency-comb spectroscopy with velocity-modulation spectroscopy (vms) and used this to measure four bands in HfF+ over a 1000cm−1 bandwidth near 800nm. Additionally, we performed targeted scans with cw-laser vms to find 15 additional bands from 9950 to 14600cm−1. We present a detailed analysis of these bands to obtain high-precision rovibrational constants, Λ-doublings, and isotope splittings for eight electronic states. We also use our results to improve theoretical predictions and discuss implications of our measurements to the eEDM experiments. These results demonstrate the application of frequency-comb and cw-vms for broadband, high-resolution spectroscopy of molecular ions.