New insights into the neutron electric dipole moment

We analyze the CP-violating electric dipole form factor of the nucleon in the framework of covariant baryon chiral perturbation theory. We give a new upper bound on the vacuum angle, |θ₀|?2.5×¹⁰⁻¹⁰$|{\theta }_0|?2.5\times {10}^{-10}$. The quark mass dependence of the electric dipole moment is discussed and compared to lattice QCD data. We also perform the matching between its representations in the three- and two-flavor theories.     

Search for the neutron EDM by crystal-diffraction method. Test experiment and future progress

Possible future progress of the crystal-diffraction neutron electric dipole moment search experiment is discussed. A storage modification of the experiment is proposed. It is demonstrated that sensitivity of the method can be a few 10⁻²⁷ e cm for the BSO crystal with the size 10×10×10 cm³ and expected luminosity of European Spallation Source (ESS).     

Towards a new measurement of the neutron electric dipole moment

Precision measurements of particle electric dipole moments (EDMs) provide extremely sensitive means to search for non-standard mechanisms of T (or CP) violation. For the neutron EDM, the upper limit has been reduced by eight orders of magnitude in 50 years thereby excluding several CP violation scenarios. We report here on a new effort aiming at improving the neutron EDM limit by two orders of magnitude, down to a level of 3 × 10⁻²⁸ e·cm. The two central elements of the approach are the use of the higher densities which will be available at the new dedicated spallation UCN source at the Paul Scherrer Institute, and the optimization of the in-vacuum Ramsey resonance technique, with storage chambers at room temperature, to reach new limits of sensitivity.     

Detection of 3He spins with ultra-low field nuclear magnetic resonance employing SQUIDs for application to a neutron electric dipole moment experiment

The precession of ³He spins is detected with ultra-low field NMR. The absolute strength of the NMR signal is accurately measured and agrees closely with theoretical calculations. The sensitivity is analyzed for applications to a neutron electric dipole moment (nEDM) fundamental symmetry experiment under development.     

Electric dipole moment of Dirac fermionic dark matter

The direct limit of electric dipole moment and direct searches for dark matter by electric dipole interaction are investigated with including the electromagnetic nuclear form factor, in case that the dark matter candidate is a Dirac particle. The electric dipole moment of dark matter constrained by direct searches must be lower than 7×¹⁰−22e cm for dark matter mass of 100 GeV to satisfy the current experimental exclusion limits at XENON10 and CDMS II. The CP violation of electric dipole moment and the dark matter discovery by electric dipole interaction in the future are considered.     

Analytic solution of the wave equation for an electron in the field of a molecule with an electric dipole moment

We relax the usual diagonal constraint on the matrix representation of the eigenvalue wave equation by allowing it to be tridiagonal. This results in a larger representation space that incorporates an analytic solution for the non-central electric dipole potential cosθ/r², which was believed not to belong to the class of exactly solvable potentials. Therefore, we were able to obtain a closed form solution of the three-dimensional time-independent Schrödinger equation for a charged particle in the field of a point electric dipole that could carry a nonzero net charge. This problem models the interaction of an electron with a molecule (neutral or ionized) that has a permanent electric dipole moment. The solution is written as a series in a basis composed of special functions that support a tridiagonal matrix representation for the angular and radial components of the wave operator. Moreover, this solution is for all energies, the discrete (for bound states) as well as the continuous (for scattering states). The expansion coefficients of the radial and angular components of the wavefunction are written in terms of orthogonal polynomials satisfying three-term recursion relations. For the Coulomb-free case, where the molecule is neutral, we calculate critical values for its dipole moment below which no electron capture is allowed. These critical values are obtained not only for the ground state, where it agrees with already known results, but also for excited states as well.     

铯原子里德堡态Stark能量及电偶极矩的测量和理论计算

里德堡原子由于具有体积大、寿命长、易极化及在外电场中能级易于操控等特点, 已经成为了目前物理学领域研究的热点之一. 本文在磁光阱中实验测量了铯原子15P_3/2和16P_3/2态的Stark光谱,根据光谱给出了15P_3/2和16P_3/2|m|=1/2 Stark态在0-1400 V/cm场强范围适用的Stark 能量和偶极矩的经验性解析表达式; 用数值方法求解薛定谔方程获得了这些态的Stark能量、偶极矩和电子几率密度分布. 电子几率密度分布定性说明了计算的偶极矩矢量的方向是正确的. 计算的Stark能量、偶极矩与实验结果相一致.     

Electric dipole moment of the neutron in the electric field of a crystal

The effect of the weak interaction on the diffraction measurement of the electric dipole moment of neutrons moving in crystal electric fields has been analyzed. It has been shown that the interference of the Schwinger interaction with the weak interaction field imposes restrictions on the measured electric dipole moment of the neutron.     

Self-force on an electric dipole in the spacetime of a cosmic string

We calculate the electrostatic self-force on an electric dipole in the spacetime generated by a static, thin, infinite and straight cosmic string. The electric dipole is held fixed in different configurations, namely, parallel, perpendicular to the cosmic string and oriented along the azimuthal direction around this topological defect, which is stretched along the z$z$ axis. We show that the self-force is equivalent to an interaction of the electric dipole with an effective dipole moment which depends on the linear mass density of the cosmic string and on the configuration. The plots of the self-forces as functions of the parameter which determines the angular deficit of the cosmic string are shown for those different configurations.     

On the effects on a Landau-type system for an atom with no permanent electric dipole moment due to a Coulomb-type potential

We analyse the bound states for a Landau-type system for an atom with no permanent electric dipole moment subject to a Coulomb-type potential. By comparing the energy levels for bound states of the system with the Landau quantization for an atom with no permanent electric dipole moment (Furtado et al., 2006), we show that the energy levels of the Landau-type system are modified, where the degeneracy of the energy levels is broken. Another quantum effect investigated is a dependence of the angular frequency of the system on the quantum numbers associated with the radial modes and the angular momentum. As examples, we obtain the angular frequency and the energy levels associated with the ground state and the first excited state of the system.     

CP-violating dipole form factors of the top quark and tau lepton in scalar leptoquark models

We calculate the CP-violating electric and weak dipole form factors of the top quark and the tau lepton in models with scalar leptoquarks coupling only to the third generation of quarks and leptons. We obtain numerical values of the real and imaginary parts of these form factors at various energies for different values of leptoquark masses and couplings. The existing limits on the tau electric and weak dipole form factors allow us to put a limit on the masses and couplings of such leptoquarks and therefore on the top electric and weak dipole form factors. We also discuss constraints on the form factors coming from indirect limits on leptoquark masses and couplings deduced from LEP results on Z properties.     

The effect of a permanent dipole moment on the polar molecule cavity quantum electrodynamics

A dressed-state perturbation theory beyond the rotating wave approximation(RWA) is presented to investigate the interaction between a two-level electronic transition of polar molecules and a quantized cavity field. Analytical expressions can be explicitly derived for both the ground- and excited-state-energy spectrums and wave functions of the system, where the contribution of permanent dipole moments(PDM) and the counter-rotating wave term(CRT) can be shown separately.The validity of these explicit results is discussed by comparison with the direct numerical simulation. Compared to the CRT coupling, PDM results in the coupling of more dressed states and the energy shift is proportional to the square of the normalized permanent dipole difference, and a greater Bloch–Siegert shift can be produced in the giant dipole molecule cavity QED. In addition, our method can also be extended to the solution of the two-level atom Rabi model Hamiltonian beyond the RWA.     

Taking into account the Earth’s rotation in experiments on the search of the electric dipole moment of the neutron

The problem of taking into account the Earth’s rotation in the search of the electric dipole moment of the neutron in experiments with ultracold neutrons and in the diffraction experiment is analyzed. For the precision reached up to the present moment in the diffraction experiment, the account of the Earth’s rotation yields a negligible (exactly calculated) correction. In experiments with ultracold neutrons, this correction exceeds the systematic error of measurement of the electric dipole moment of the neutron, and its exact calculation requires additional investigations. In this regard, further development of the diffraction method should considerably promote the progress in the search of the electric dipole moment of the neutron.     

New measurements and global analysis of rotational spectra of Cl-, Br-, and I-benzene: Spectroscopic constants and electric dipole moments

The data available from rotational spectroscopy for chlorobenzene, bromobenzene, and iodobenzene have been extended by new measurements in the mm-wave region and in supersonic expansion in the cm-wave region. All available ground state measurements have been combined in global fits to derive precise rotational, centrifugal, and nuclear quadrupole coupling constants for the molecules. Rotational transitions in first excited states of the lowest frequency normal modes in bromobenzene and iodobenzene have been assigned and fitted. The values of electric dipole moments for ³⁵Cl-, ⁷⁹Br-, ⁸¹Br-, and I-benzene have been determined from Stark effect measurements on selected hyperfine components in the supersonic expansion spectrum, and are compared with values for several other series of monohalogen molecules.     

Redoubled effect of a neutron spin rotation in deformed noncentrosymmetric crystal for the Bragg diffraction scheme

JETP Letters - A doubled effect of a neutron spin rotation in a noncentrosymmetric quartz crystal for the Bragg reflected neutrons from the deformed exit crystal side is first observed. The effect...     

原子自发辐射中偶极矩的涨落与最大纠缠态的保持

研究了二能级原子与电磁场相互作用体系的自发辐射与量子纠缠态.在原子的自发辐射过程中,其偶极矩的期待值总是零,但偶极矩的涨落恒等于一个不为零的常量,因此原子的自发辐射是由真空起伏导致偶极矩的涨落引起的.Jaynes-Cummings模型是产生量子纠缠态的重要体系,研究发现,原子与场纠缠态的信息熵和纠缠度随时间作周期性的振荡,量子态在非纠缠与纠缠态之间变化.更为重要的是,在失谐量适当时,量子态将长时间停留在最大纠缠态.     

Ab initio dipole moment and theoretical rovibrational intensities in the electronic ground state of PH3

We report a six-dimensional CCSD(T)/aug-cc-pVTZ dipole moment surface for the electronic ground state of PH₃ computed ab initio on a large grid of 10 080 molecular geometries. Parameterized, analytical functions are fitted through the ab initio data, and the resulting dipole moment functions are used, together with a potential energy function determined by refining an existing ab initio surface in fittings to experimental wavenumber data, for simulating absorption spectra of the first three polyads of PH₃, i.e., (ν₂, ν₄), (ν₁, ν₃, 2ν₂, 2ν₄, ν₂ + ν₄), and (ν₁ + ν₂, ν₃ + ν₂, ν₁ + ν₄, ν₃ + ν₄, 2ν₂ + ν₄, ν₂ + 2ν₄, 3ν₂, 3ν₄). The resulting theoretical transition moments show excellent agreement with experiment. A line-by-line comparison of the simulated intensities of the ν₂/ν₄ band system with 955 experimental intensity values reported by Brown et al. [L.R. Brown, R.L. Sams, I. Kleiner, C. Cottaz, L. Sagui, J. Mol. Spectrosc. 215 (2002) 178-203] gives an average absolute percentage deviation of 8.7% (and a root-mean-square deviation of 0.94 cm⁻¹ for the transition wavenumbers). This is very remarkable since the calculations rely entirely on ab initio dipole moment surfaces and do not involve any adjustment of these surfaces to reproduce the experimental intensities. Finally, we predict the line strengths for transitions between so-called cluster levels (near-degenerate levels formed at high rotational excitation) for J up to 60.     

Theory of the polarization of highly charged ions in storage rings: Production, preservation, observation and application to the search for a violation of the fundamental symmetries

Theoretical concepts for the production, preservation and control of polarized highly charged ion beams in storage rings are investigated. It is argued that hydrogen-like ions can be polarized efficiently by optical pumping of the Zeeman sublevels of ground state hyperfine levels and that the maximum achievable nuclear polarization exceeds 90%. In order to study the preservation of the polarization during the ion motion through the magnetic system of the ring, the concept of the instantaneous quantization axis is introduced. It is suggested that the employment of “Siberian snakes” may help to preserve the ion beam polarization in the ring. The control of the beam polarization can be achieved by different methods: by measuring the Stokes parameters for the emitted photons or by observing the angular dependence of the transition rates for polarized ions. The important motivation for the production of polarized ion beams is the possibility to observe parity nonconservation effects in the hyperfine-quenched transitions in helium-like highly charged ions, where these effects can reach an unprecedented high value for atomic physics. The possible observation of parity nonconservation effects connected with the nuclear anapole moment is also discussed. A method for the observation of the electric dipole moment of an electron in a storage ring with a polarized highly charged ion beam is proposed. This method allows, in principle, to improve the existing boundaries for the electric dipole moment of an electron. However, the requirements of the corresponding experiment are very stringent.