Neutron Moment Research Articles

Erratum: Neutron and electron electric dipole moment inN=1supergravity unification [Phys. Rev. D 57, 478 (1998)

Erratum: Neutron and electron electric dipole moment in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>1</mml:mn><mml:mn /></mml:math>supergravity unification [Phys. Rev. D 57, 478 (1998)

Electron and neutron electric dipole moments in the constrained MSSM

We analyze the effects of CP-violating phases on the electric dipole moment (EDM) of electron and neutron in the constrained minimal supersymmetric model. We find that the phases phi_{\mu} and phi_{A_0} have to be strongly correlated, in particular for small values of the SUSY mass parameters. We calculate the neutron EDM in two different models, the Quark-Parton Model and the Chiral Quark Model. It turns out that the predictions are quite sensitive to the model used. We show parameter regions in the M_0-M_1/2 plane which are excluded by considering simultaneously the experimental bounds of both electron and neutron EDM, assuming specific values for the phases phi_{\mu} and phi_{A_0}.

CP-odd tadpole renormalization of Higgs scalar-pseudoscalar mixing

We consider an Abelian model with a CP-conserving Higgs potential spanned by two complex Higgs fields. The CP invariance of the Higgs potential is then broken explicitly beyond the Born approximation by introducing soft-CP-violating Yukawa interactions. Based on the non-renormalization theorem, we derive the consistency conditions under which a CP-odd counterterm exists and, at the same time, renders the one-loop-induced mixing of a CP-even Higgs boson with a CP-odd Higgs scalar ultra-violet finite. The novel CP-odd tadpole renormalization may then be determined from the minimization constraints on the Higgs potential. Finally, we discuss the phenomenological consequences of the so-generated CP-violating scalar-pseudoscalar mixing for the electric dipole moments of neutron, electron and muon.

CPviolation in theμ→3eprocess and supersymmetric grand unified theory

A triple vector correlation in the $\mu^{+} \to e^{+} e^{+} e^{-}$ decay with polarized muons is investigated as a probe to CP violating coupling constants in supersymmetric models. A sizable triple correlation can be induced due to a complex phase in the supersymmetric soft-breaking terms in the SU(5) grand unified theory. Correlation with the electric dipole moments of electron and neutron are investigated and it is shown that these quantities give independent information on possible CP violating sources.

Erratum: Neutron and electron electric dipole moment inN=1supergravity unification [Phys. Rev. D57, 478 (1998)

Erratum: Neutron and electron electric dipole moment in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>1</mml:mn><mml:mn /></mml:math>supergravity unification [Phys. Rev. D<b>57</b>, 478 (1998)

Solving the supersymmetric CP problem with Abelian horizontal symmetries

Models that combine Abelian horizontal symmetries and spontaneous CP violation can (i) explain the smallness and hierarchy in quark parameters; (ii) satisfactorily suppress supersymmetric contributions to flavor changing neutral current processes; (iii) solve the μ-problem; and (iv) suppress supersymmetric contributions to CP violating observables to an acceptable level. The CKM phase is O (1) and responsible, through Standard Model box diagrams, to ϵ K . The supersymmetric CP violating phases are suppressed, φ A ∼ λ 6 and φ B ∼ λ 8 (λ ∼ 0.2), leading to an electric dipole moment of neutron that is about 2–3 orders of magnitude below the experimental bound.

Gd isotope systematics with Skyrme and delta -pairing forces.

Assuming axial symmetry of the nuclear shape and the Skyrme force SIII updated on the pairing interaction {ital V}{sub 0}{delta}({ital r}{searrow}{sub 12}) we performed constrained Hartree-Fock calculations of well deformed even gadolinium {sub 64}Gd isotopes with neutron numbers {ital N}=86{endash}106. The mass spectrum, nuclear radii, neutron skin thickness, quadrupole moments (deformations), and low-spin rotational levels are calculated. In all the cases viewed the angular momentum projection after variation was performed. This was achieved by explicit inclusion of the rotational energy {minus}{l_angle}{cflx {sq_bullet}}{sup 2}{r_angle}/2J. The procedure corrects the ground state deformations and gives deformations and energies of low excited states as well. The results found have all been compared to experimental data. {copyright} {ital 1996 The American Physical Society.}

Vacuum structure, chiral symmetry breaking and electric dipole moment of neutron

Considering a CP-violating QCD interaction, the electric dipole moment of neutron (EDMN) is estimated in a quark model of light mesons with a dynamical breaking of chiral symmetry through a non-trivial vacuum structure. Pion and kaon, being treated consistently within the model, yield to the constituent quark wave functions as well as the dynamical quark masses and thus determine the constituent quark field operators with respect to light quark flavors. Using the translationally invariant hadronic states and these constituent quark field operators, the EDMN estimated here remains well within the recent experimental bound ofD n<11 × 10−26 e-cm with the CP-violation parameter |ϑ|=10−8, which in fact accounts for a strong CP-violation.

Explicit CP violation of the Higgs sector in the next-to-minimal supersymmetric standard model.

We study the explicit $CP$ violation of the Higgs sector in the minimal supersymmetric standard model with a gauge singlet Higgs field. The magnitude of $CP$ violation is discussed in the limiting cases of $x\gg v_1,\ v_2$ and $x\ll v_1,\ v_2$, where $x$ and $v_{1,2}$ denote VEV of singlet and doublet Higgs scalars, respectively. Our numerical predictions of the electric dipole moments of electron and neutron lie around the present experimental upper limits. It is found that the large $CP$ violation effect reduces the magnitude of the lightest Higgs boson mass in the order of a few ten GeV.

Electric dipole moments of neutron and electron in two-Higgs-doublet model with maximal CP violation

We study the electric dipole moments (EDM) of the neutron and the electron in the two-Higgs-doublet model, in the case that CP symmetry is violated maximally in the neutral Higgs sector. We take account of the Weinberg's operator O 38 = GG barG as well as the operator O q8 = qσ Gq for the neutron, and the Barr-Zee diagrams for the electron. It is found that the predicted neutron EDM could be considerably reduced by the destructive contribution of the two Higgs scalars to get the lower value than the experimental bound. As to the electron EDM, the predicted value is smaller in one order than the experimental one.

CP violation in a multi higgs doublet model

We study CP violation in a multi-Higgs doublet model based on a $S_3 \times Z_3$ horizontal symmetry. We consider two mechanisms for CP violation in this model: a) CP violation due to complex Yukawa couplings; and b) CP violation due to scalar-pseudoscalar mixings. We find that the predictions for $\epsilon'/\epsilon$, CP violation in B decays and the electric dipole moments of neutron and electron are different between these two mechanisms. These predictions are also dramatically different from the minimal Standard Model predictions.

ELECTRIC DIPOLE MOMENT OF NEUTRON IN A FIELD THEORETIC QUARK MODEL

Electric Dipole Moment of Neutron (EDMN) is considered in a field theoretic quark model of composite hadrons. For this purpose CP-violating QCD interaction is used and the calculation is based on the second order perturbation. With harmonic oscillator radius of neutron as a free parameter, the theoretical analysis is observed to agree reasonably well with the experiment.

An estimate of the uncertainty due to counting statistics in a novel type of neutron EDM experiment

A novel type of EDM experiment using ultracold neutrons produced in a superthermal source, coupled with the dressed neutron technique has been proposed. Here an estimate is made of the uncertainty in the electric dipole moment of neutron that would arise from neutron counting statistics an experiment.

Polarized neutron reflectometry

Polarized neutron reflectometry is a powerful technique for studying the microscopic magnetic structures in thin films and multilayers. The corresponding analysis of spin-dependent reflectivity data is discussed and illustrated with a number of specific examples. The measurement of the precession of the neutron moment within a nonmagnetic medium, but in the presence of an applied field, as a means of determining the nuclear density profile is also considered.

Light WR and the Spontaneous CP Violation. II

In our previous paper, we examined a possibility of light WR in the framework of the SU(2)L ×SU(2)R ×U(1) model with spontaneous CP violation, by assuming a special form of the right-handed KM matrix KR in the CP conserving limit. Here we examine another possibility of KR. We show that the model allows MWR ≃400 ∼800 GeV depending on mt. In this model, the CP violations in K meson decays are due to the right-handed interaction. The model predicts both positive and negative values of ε'/ε, but its magnitude is smaller than 0.6 ×10-3 for MWR ≪ 1 TeV. The electric dipole moment of neutron is predicted to be of order 10-27 e·cm. CP violating asymmetries in B meson decays are too small to be detected.

Exotic fermions and electric dipole moments.

The contributions of mirror fermions to the electric dipole moments (EDM's) of leptons and neutrons are studied using the available limits on the mixing of the relevant fermions to their mirror partners. These limits imply EDM's several orders of magnitude larger than the current experimental bounds in the case of the electron and the neutron if the relevant $\mathrm{CP}$-violating phases are not unnaturally small. If these phases are large, then the bounds on the EDM's can be used to improve upon the limits on mixing between the ordinary ($f$) and the mirror ($F$) fermions. In the specific case of the latter mixing angle being given by ${(\frac{{m}_{f}}{{M}_{F}})}^{\frac{1}{2}}$, one can obtain the electron and the neutron EDM's close to experimental bounds.

Neutron electric dipole moment in left-right-symmetric models.

We show that in a left-right-symmetric gauge theory, when the left-right mixing is nonzero the leading contribution to the electric dipole moment of neutron may be due to the two-loop, purely gluonic mechanism of Weinberg.

Light WR and the Spontaneous CP Violation

In the framework of the SU(2)L ×SU(2)R ×U(1) model with spontaneous CP violation, a possibility of light WR is examined. We constructed a model which allows MWR ∼400 GeV. This model shows quite different features from the standard model : (i) The CP violation in K →ππ decay is mainly from the right-handed interaction. (ii) The CP violations in Bd- \barBd mixing and the direct decays of Bd are small. In contrast, for the Bs meson the large CP asymmetries for both nonleptonic (20%) and semileptonic (20%) decays may appear through Bs-Bs mixing in some domain of MWR and mt. (iii) The electric dipole moment of neutron is as large as 10-26e ·cm .

Fermion electric dipole moments, muon polarization inη→μμ¯,KL0→μμ¯ decays, and the scalar-pseudoscalar mixing mechanism

We construct extended Higgs-boson models of soft CP-invariance violation arising from scalar-pseudoscalar mixing. Using the electric dipole moment of neutron as input, we find that the charged-lepton electric dipole moments scale as (mass${)}^{3}$. They are estimated to be 2.1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}28}$, 4.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}22}$, and 1.8\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}19}$ e cm for electron, muon, and \ensuremath{\tau}, respectively. An important test of this source of CP violation lies in the longitudinal polarizations of muon in \ensuremath{\eta}\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\mu}\ifmmode\bar\else\textasciimacron\fi{} and ${K}_{L}^{0}$\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\mu}\ifmmode\bar\else\textasciimacron\fi{}, which we estimate to be of the order of ${10}^{\mathrm{\ensuremath{-}}2}$ and ${10}^{\mathrm{\ensuremath{-}}1}$, respectively.

Texture Investigations by Neutron Time‐of‐Flight Diffraction

For the majority of isotopes the thermal neutron absorption cross section is two or more orders lower than that for X‐rays. This makes neutron diffraction well‐suited for bulk texture investigations. Some characteristics of neutron diffraction are discussed. The principles of neutron time‐of‐flight diffraction are described. The pole figure determination by means of TOF technique is considered. The main parameters of the present Dubna texture facility are given. Further developments of the experimental technique are considered. The application of the TOF technique for inverse pole figure measurement is discussed as an approach to direct observation of the texture forming process. The magnetic moments of neutrons can be used to study magnetic textures. Two different techniques are discussed.