Neutron Electric Dipole Moment Research Articles

MASS TERMS OF CP-VIOLATING WEINBERG THREE-HIGGS-DOUBLET MODEL AT A CHARGE-BREAKING VACUUM

Weinberg three-Higgs-doublet model attracts interest in many aspects including the study of CP-violation as well as calculating the muon transverse polarization and neutron electric dipole moment. In the present work, we calculate the mass terms of CP-violating Weinberg 3HDM at a charge-breaking vacuum using an elaboratre basis.

Neutron electric dipole moment constraint on scale of minimal left-right symmetric model

Using an effective field theory approach, we calculate the neutron electric dipole moment (nEDM) in the minimal left-right symmetric model with both explicit and spontaneous CP violations. We integrate out heavy particles to obtain flavor-neutral CPviolating effective Lagrangian. We run the Wilson coefficients from the electroweak scale to the hadronic scale using one-loop renormalization group equations. Using the state-of-theart hadronic matrix elements, we obtain the nEDM as a function of right-handed W-boson mass and CP-violating parameters. We use the current limit on nEDM combined with the kaon-decay parameter ϵ to provide the most stringent constraint yet on the left-right symmetric scale $$M_{w_{R}}> (10 \pm 3) {\rm TeV} $$ .

P-odd and CP-odd four-quark contributions to neutron EDM

In a class of beyond-standard-model theories, CP-odd observables, such as the neutron electric dipole moment, receive significant contributions from flavor-neutral P-odd and CP-odd four-quark operators. However, considerable uncertainties exist in the hadronic matrix elements of these operators strongly affecting the experimental constraints on CP-violating parameters in the theories. Here we study their hadronic matrix elements in combined chiral perturbation theory and nucleon models. We first classify the operators in chiral representations and present the leading-order QCD evolutions. We then match the four-quark operators to the corresponding ones in chiral hadronic theory, finding symmetry relations among the matrix elements. Although this makes lattice QCD calculations feasible, we choose to estimate the non-perturbative matching coefficients in simple quark models. We finally compare the results for the neutron electric dipole moment and P-odd and CP-odd pion-nucleon couplings with the previous studies using naive factorization and QCD sum rules. Our study shall provide valuable insights on the present hadronic physics uncertainties in these observables.

The2H Electric Dipole Moment in a Separable Potential Approach

Measurement of the electric dipole moment (EDM) of 2 H or of 3 He may well come prior to the cov- eted measurement of the neutron EDM. Exact model calculations for the deuteron are feasible, and we explore here the model dependence of such deuteron EDM calculations. We investigate in a separable potential approach the relationship of the full model calculation to the plane wave approximation, correct an error in an early poten- tial model result, and examine the tensor force aspects of the model results as well as the e ect of the short range repulsion found in the realistic, contemporary potential model calculations of Liu and Timmermans. We conclude that, because one-pion exchange dominates the EDM calculation, separable potential model calculations should provide an adequate picture of the 2 H EDM until better than 10% measurements are achieved.

Neutron electric dipole moment in the gauge-Higgs unification

We study the neutron electric dipole moment (EDM) in a five-dimensional $SU(3)$ gauge-Higgs unification compactified on ${M}^{4}\ifmmode\times\else\texttimes\fi{}{S}^{1}/{Z}_{2}$ space-time including a massive fermion. We point out that to realize the $CP$ violation is a nontrivial task in the gauge-Higgs unification scenario and argue how the $CP$ symmetry is broken spontaneously by the vacuum expectation value of the Higgs, the extra space component of the gauge field. We emphasize the importance of the interplay between the vacuum expectation value of the Higgs and the ${Z}_{2}$-odd bulk mass term to get physically the $CP$ violation. We then calculate the one-loop contributions to the neutron EDM as the typical example of the $CP$ violating observable and find that the EDM appears already at the one-loop level, without invoking the three-generation scheme. We then derive a lower bound for the compactification scale, which is around 2.6 TeV, by comparing the contribution due to the nonzero Kaluza-Klein modes with the experimental data.

Neutron diffraction test on spin-dependent short range interaction

The direct constraint on the parameters of short range pseudomagnetic interaction of free neutron with matter is obtained from the recent test experiment on a search for neutron EDM by crystal-diffraction method. It is shown that this constraint on a product of scalar to pseudo-scalar coupling constants $g_s g_p$ is better than that of any other method for the range $\lambda < 10^{-5}$cm.

NEUTRON ELECTRIC DIPOLE MOMENT AT FIXED TOPOLOGY

We describe the finite volume effects of CP-odd quantities, such as the neutron electric dipole moment and the anapole moment in the θ-vacuum, under different topological sectors. We evaluate the three-point Green's functions for the electromagnetic current in a fixed nontrivial topological sector in order to extract these CP-odd observables. We discuss the role of zero modes in the CP-odd Green's function and show that, in the quenched approximation, there is a power divergence in the quark mass for CP-odd quantities at finite volume.

Measurement of the neutron electric dipole moment by crystal diffraction

An experiment using a prototype setup to search for the neutron electric dipole moment by measuring spin rotation in a non-centrosymmetric crystal (quartz) was carried out to investigate statistical sensitivity and systematic effects of the method. It has been demonstrated that the concept of the method works. The preliminary result of the experiment is d n = ( 2.5 ± 6.5 ) × 10 - 24 e cm . The experiment showed that an accuracy of ~ 2.5 × 10 - 26 e cm can be obtained in 100 days data taking, using available quartz crystals and neutron beams.

Relaxation of spin-polarizedH3ein mixtures ofH3eandH4eat about 330 mK

We report the measurements of depolarization probabilities of polarized $^3$He in a rectangular acrylic cell with a deuterated tetraphenyl butadiene-doped deuterated polystyrene coating filled with superfluid $^4$He at $\sim$330 mk with a magnetic holding field of $\sim$7.3 G. We achieve a wall depolarization probability of $\sim1.0\times10^{-7}$. Such a surface will find application in a new experiment searching for the neutron electric dipole moment and other applications.

Towards a new measurement of the neutron electric dipole moment

The effort towards a new measurement of the neutron electric dipole moment (nEDM) at the Paul Scherrer Institut's (PSI) new high intensity source of ultracold neutrons (UCN) is described. The experimental technique relies on Ramsey's method of separated oscillatory fields, using UCN in vacuum with the apparatus at ambient temperature. In the first phase, R&D towards the upgrade of the RAL/Sussex/ILL apparatus is being performed at the Institut Laue-Langevin (ILL). In the second phase the apparatus, moved from ILL to PSI, will allow an improvement in experimental sensitivity by a factor of 5. In the third phase, a new spectrometer should gain another order of magnitude in sensitivity. The improvements will be mainly due to (1) much higher UCN intensity, (2) improved magnetometry and magnetic field control, and (3) a double chamber configuration with opposite electric field directions.

Ultracold-neutron infrastructure for the PNPI/ILL neutron EDM experiment

A PNPI/ILL experiment to measure the neutron electric dipole moment (EDM) is currently being prepared at the facility PF2 for ultracold neutrons (UCN) at the Institut Laue-Langevin in Grenoble. To enable an improvement of sensitivity, one of PF2's beam positions has been equipped with new components for UCN transport, polarization and beam characterization, comprised of a superconducting solenoid-polarizer with magnetic field 4 T, a neutron guide system with diameter 136 mm prepared in replica technology, and a novel beam chopper for time-of-flight analysis. The whole EDM apparatus is set up on a non-magnetic platform. The total flux of polarized UCN with velocities less than 6.8 m/s along the guide axis is 1.5×10 5 n/s, corresponding to a flux density of 10 3 cm −2 s −1. The density of polarized UCN at the experimental position is about 5 cm −3, which shall lead to an EDM measurement with a counting statistical accuracy of 1.5×10 −26 ecm during 200 days of operation at PF2.

CryoEDM: A cryogenic experiment to measure the neutron electric dipole moment

CryoEDM is an experiment that aims to measure the electric dipole moment (EDM) of the neutron to a precision of 10 −28 e cm. A description of CryoEDM, the apparatus, technologies and commissioning is presented.

Perspectives for nEDM Search by Crystal Diffraction. Test Experiment and Results

An experiment searching for the neutron electric dipole moment by measuring spin-rotations in a non-centrosymmetric crystal was carried out to investigate the statistical sensitivity and systematic effects of the method. The preliminary result of this experiment is d n = ( 2.5 ± 6.5 ) ⋅ 10 − 24 e ⋅ cm . The performance was essentially limited by the low luminosity of the prototype setup. With a dedicated setup and a large quartz crystal, the expected accuracy is ∼ 2 ⋅ 10 − 26 e ⋅ cm for 100 days of data collection.

Upper limits on electric dipole moments of τ-lepton and W-boson

We discuss new upper limits on the electric dipole moments (EDM) of the τ-lepton and W-boson, which follow from the precision measurements of the electron and neutron EDM.

Neutron electric dipole moment measurements at the ILL

The origin of the CP violation which created the matter in the universe is one of the enduring mysteries of fundamental physics. Particle electric dipole moments provide a sensitive probe of CP violation from new physics. The article describes past and future work being done at the ILL in Grenoble to search for an electric dipole moment of the neutron.

Universality of mixed action extrapolation formulae

Mixed action theories with chirally symmetric valence fermions exhibit very desirable features both at the level of the lattice calculations as well as in the construction and implementation of the low energy mixed action effective field theory. In this work we show that when such a mixed action effective field theory is projected onto the valence sector, both the Lagrangian and the extrapolation formulae become universal in form through next to leading order, for all variants of discretization methods used for the sea fermions. Our conclusion relies on the chiral nature of the valence quarks. The result implies that for all sea quark methods which are in the same universality class as QCD, the numerical values of the physical coefficients in the various mixed action chiral Lagrangians will be the same up to lattice spacing dependent corrections. This allows us to construct a prescription to determine the mixed action extrapolation formulae for a large class of hadronic correlation functions computed in partially quenched chiral perturbation theory at the one-loop level. For specific examples, we apply this prescription to the nucleon twist--2 matrix elements and the nucleon--nucleon system. In addition, we determine the mixed action extrapolation formula for the neutron EDM as this provides a nice example of a theta-dependent observable; these observables are exceptions to our prescription.

The effective theory of the light stop scenario

Electroweak baryogenesis in the minimal supersymmetric extension of the Standard Model may be realized within the light stop scenario, where the right-handed stop mass remains close to the top-quark mass to allow for a sufficiently strong first order electroweak phase transition. All other supersymmetric scalars are much heavier to comply with the present bounds on the Higgs mass and the electron and neutron electric dipole moments. Heavy third generation scalars render it necessary to resum large logarithm contributions to perform a trustable Higgs mass calculation. We have studied the one-loop RGE improved effective theory below the heavy scalar mass scale and obtained reliable values of the Higgs mass. Moreover, assuming a common mass for all heavy scalar particles, and values of all gaugino masses and the Higgsino mass parameter about the weak scale, and imposing gauge coupling unification, a two-loop calculation yields values of the mass in the interval between three TeV and six hundred TeV. Furthermore for a stop mass around the top quark mass, this translates into an upper bound on the Higgs mass of about 150 GeV. The Higgs mass bound becomes even stronger, of about 129 GeV, for the range of stop and gaugino masses consistent with electroweak baryogenesis. The collider phenomenology implications of this scenario are discussed in some detail.

Electric dipole moments in the MSSM reloaded

We present a detailed study of the Thallium, neutron, Mercury and deuteron electric dipole moments (EDMs) in the CP-violating Minimal Supersymmetric extension of the Standard Model (MSSM). We take into account the complete set of one-loop graphs, the dominant Higgs-mediated two-loop diagrams, the complete CP-odd dimension-six Weinberg operator and the Higgs-mediated four-fermion operators. We improve upon earlier calculations by including the resummation effects due to CP-violating Higgs-boson mixing and to threshold corrections to the Yukawa couplings of all up- and down-type quarks and charged leptons. As an application of our study, we analyse the EDM constraints on the CPX, trimixing and Maximally CP- and Minimally Flavour-Violating (MCPMFV) scenarios. Cancellations may occur among the CP-violating contributions to the three measured EDMs arising from the 6 CP-violating phases in the MCPMFV scenario, leaving open the possibility of relatively large contributions to other CP-violating observables. The analytic expressions for the EDMs are implemented in an updated version of the code CPsuperH2.0.

Low energy probes of CP violation in a flavor blind MSSM

We analyze the low energy implications of a flavor blind supersymmetric scenario (where the CKM matrix is the only source of flavor violation) in the presence of new CP violating but flavor conserving phases in the soft sector. We find that the best probes of this rather restricted scenario are (i) the electric dipole moments (EDMs) of the electron (de) and the neutron (dn) and (ii) flavor changing and CP violating processes in B systems, like the CP asymmetries in b→sγ and B→ϕ(η′)KS, i.e. ACP(b→sγ) and Sϕ(η′)KS, respectively. The non-standard values for Sϕ(η′)KS, measured at the B factories, can find a natural explanation within our scenario and this would unambiguously imply (i) positive and often large (non-standard) values for ACP(b→sγ) and (ii) a lower bound for the electron and neutron EDMs at the level of de,n≳10−28ecm. Moreover, we predict positive New Physics (NP) contributions to ϵK which could be welcomed in view of the recently lowered Standard Model value for ϵK. Interestingly, an explanation for the non-standard values for Sϕ(η′)KS can also naturally lead to an explanation for the anomaly of the muon anomalous magnetic moment. Finally, we outline the role and the interplay of the direct NP searches at the LHC with the indirect searches performed by low energy flavor physics observables.

Storage of ultracold neutrons in high resistivity, non-magnetic materials with high Fermi potential

We report the use of deuterated polystyrene (dPS) and deuterated polyethylene (dPE) for the storage of ultracold neutrons (UCN) in an experiment to search for a finite neutron electric dipole moment (nEDM). The Fermi potential of thin film coatings on silicon was measured by cold neutron reflectometry as V(dPS)=(161±10) neV and V(dPE)=(214±10) neV. The UCN loss factor at room temperature of a dPS-coated polystyrene insulator is η=(3±1)×10 −4.