Ivan Kozyryev

Order of Magnitude Smaller Limit on the Electric Dipole Moment of the Electron

Stubbornly Spherical The shape of the electrons charge distribution reflects the degree to which switching the direction of time impacts the basic ingredients of the universe. The Standard Model (SM) of particle physics predicts a very slight asphericity of the charge distribution, whereas SM extensions such as supersymmetry posit bigger and potentially measurable, but still tiny, deviations from a perfect sphere. Polar molecules have been identified as ideal settings for measuring this asymmetry, which should be reflected in a finite electric dipole moment (EDM) because of the extremely large effective electric fields that act on an electron inside such molecules. Using electron spin precession in the molecule ThO, Baron et al. (p. 269, published online 19 December; see the cover; see the Perspective by Brown) measured the EDM of the electron as consistent with zero. This excludes some of the extensions to the SM and sets a bound to the search for a nonzero EDM in other facilities, such as the Large Hadron Collider. Spin precession measurements in the polar molecule thorium monoxide indicate a nearly spherical charge distribution of an electron. [Also see Perspective by Brown] The Standard Model of particle physics is known to be incomplete. Extensions to the Standard Model, such as weak-scale supersymmetry, posit the existence of new particles and interactions that are asymmetric under time reversal (T) and nearly always predict a small yet potentially measurable electron electric dipole moment (EDM), de, in the range of 10−27 to 10−30 e·cm. The EDM is an asymmetric charge distribution along the electron spin (S→) that is also asymmetric under T. Using the polar molecule thorium monoxide, we measured de = (–2.1 ± 3.7stat ± 2.5syst) × 10−29 e·cm. This corresponds to an upper limit of | de | < 8.7 × 10−29 e·cm with 90% confidence, an order of magnitude improvement in sensitivity relative to the previous best limit. Our result constrains T-violating physics at the TeV energy scale.

Methods, Analysis, and the Treatment of Systematic Errors for the Electron Electric Dipole Moment Search in Thorium Monoxide

We recently set a new limit on the electric dipole moment of the electron (eEDM) (J Baron et al and ACME collaboration 2014 Science 343 269–272), which represented an order-of-magnitude improvement on the previous limit and placed more stringent constraints on many charge-parity-violating extensions to the standard model. In this paper we discuss the measurement in detail. The experimental method and associated apparatus are described, together with the techniques used to isolate the eEDM signal. In particular, we detail the way experimental switches were used to suppress effects that can mimic the signal of interest. The methods used to search for systematic errors, and models explaining observed systematic errors, are also described. We briefly discuss possible improvements to the experiment.

Precision Measurement of Time-Reversal Symmetry Violation with Laser-Cooled Polyatomic Molecules

Precision searches for time-reversal symmetry violating interactions in polar molecules are extremely sensitive probes of high energy physics beyond the standard model. To extend the reach of these probes into the PeV regime, long coherence times and large count rates are necessary. Recent advances in laser cooling of polar molecules offer one important tool-optical trapping. However, the types of molecules that have been laser cooled so far do not have the highly desirable combination of features for new physics searches, such as the ability to fully polarize and the existence of internal comagnetometer states. We show that by utilizing the internal degrees of freedom present only in molecules with at least three atoms, these features can be attained simultaneously with molecules that have simple structure and are amenable to laser cooling and trapping.

Proposal for laser cooling of complex polyatomic molecules

An experimentally feasible strategy for direct laser cooling of polyatomic molecules with six or more atoms is presented. Our approach relies on the attachment of a metal atom to a complex molecule, where it acts as an active photon cycling site. We describe a laser cooling scheme for alkaline earth monoalkoxide free radicals taking advantage of the phase space compression of a cryogenic buffer-gas beam. Possible applications are presented including laser cooling of chiral molecules and slowing of molecular beams using coherent photon processes.

Collisional relaxation of vibrational states of SrOH with He at 2 K

Vibrational relaxation of strontium monohydroxide (SrOH) molecules in collisions with helium (He) at 2 K is studied. We find the diffusion cross section of SrOH at 2.2 K to be and the vibrational quenching cross section for the (100) Sr–O stretching mode to be . The resulting ratio is more than an order of magnitude smaller than for previously studied few-atom radicals (Au et al 2014 Phys. Rev. A 90 032703 ). We also determine the Franck–Condon factor for SrOH () to be .

Fluorescence branching ratios and magnetic tuning of the visible spectrum of SrOH

Abstract The magnetic tuning of the low rotational levels in the X 2 Σ + (0,0,0), A 2 Π r (0,0,0), and B 2 Σ + (0,0,0) electronic states of strontium hydroxide, SrOH, have been experimentally investigated using high resolution optical field-free and Zeeman spectroscopy of a cold molecular beam sample. The observed Zeeman shifts and splittings are successfully modeled using a traditional effective Hamiltonian approach to account for the interaction between the A 2 Π r and B 2 Σ + states. The determined magnetic g-factors for the X 2 Σ + , A 2 Π r , and B 2 Σ + states are compared to those predicted by perturbation theory. The dispersed fluorescence resulting from laser excitation of rotationally resolved branch features of the 0 0 0 B 2 Σ + ← X 2 Σ + , 0 0 0 A 2 Π 3 / 2 ← X 2 Σ + and 0 0 0 A 2 Π 1 / 2 ← X 2 Σ + transitions have been recorded and analyzed. The measured fluorescence branching ratios are compared with Franck-Condon calculations. The required bending motion wave functions are derived using a discrete variable representation (DVR) method. Implications for laser slowing and magneto-optical trapping experiments for SrOH are described.

Clinical Assessment of Disease Risk Factors Using SNP Data and Bayesian Methods

Recent groundbreaking technological and scientific achievements impelled the field of personalized medicine (PM), which promises to start a new era in clinical disease treatment. However, the degree of success of PM strongly depends on the establishment of a vast resource library containing the connections between many common complex diseases and specific genetic signatures. Particularly, these connections can be discovered performing whole-genome association studies, which attempt to link diseases to their genetic origins. Such large-scale surveys, combined with modern advanced statistical methods, have already identified many disease-related genetic variants. In this review, we describe in detail novel statistical methods based on Bayesian data analysis ideas—Bayesian modeling, Bayesian variable partitioning, and Bayesian graphs and networks—which are promising to help shine light on complex biological processes involved in disease formation and development. Particularly, we outline how to use Bayesian approaches in the context of clinical applications to perform epistasis analysis while accounting for the block-type genome structure.