Tensor Coupling Constants Research Articles

Spin density wave in the strongly dimerized quasi-one-dimensional organic conductor (DMET-TTF) 2AuBr2

At ambient pressure, studies of resistivity, magnetic susceptibility, and carbon-13 nuclear magnetic resonance (NMR) were conducted on the quasi-one-dimensional organic conductor ${(\text{DMET-}\mathrm{TTF})}_{2}{\mathrm{AuBr}}_{2}$. Resistivity measurements showed a broad minimum at approximately 160 K, and the insulator behavior below this temperature and magnetic susceptibility results revealed a dip structure at 22 K. At the same temperature, a sharp peak in the temperature dependence of ${T}_{1}^{\ensuremath{-}1}$ associated with the antiferromagnetic (AFM). transition was found, along with drastic splitting of the NMR spectra, indicating a commensurate AFM structure. The amplitude of the magnetic moments was determined to be $0.06{\ensuremath{\mu}}_{B}$/molecule from the hyperfine coupling constant tensor and the angular dependence of the internal field in the AFM phase. The small magnetic moment signifies the AFM nesting type, i.e., commensurate spin density wave. An antiferromagnetic ordering of $(\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\downarrow}\ensuremath{\downarrow})$ along the one-dimensional chain is expected from the $2{k}_{\mathrm{F}}$ instability. This behavior can be explained by the strong dimerization of the one-dimensional DMET-TTF chain.

Trapping sites of Li atom in the rare gas crystals Ar, Kr, and Xe: Analysis of stability and manifestation in the EPR spectra

The classical model of an ideal crystal, parametrized according to non-empirical calculations, is used to determine the structure and geometry of the atomic lithium trapping sites in solid inert gases RG = Ar, Kr, and Xe, and to define their thermodynamic stability. The diversity of the observed stable sites reduces to four highly symmetric structures corresponding to the interstitial introduction of an Li atom, its substitution of an inert gas atom, or its incorporation into tetrahedral and octahedral vacancies formed by the removal of four and six inert gas atoms from the crystal lattice. The non-empirically calculated dependences of the isotropic hyperfine coupling constant tensor on the distance in the diatomic Li@RG complex are used to estimate the shifts of the electron paramagnetic resonance signals in the predicted thermodynamically stable sites. A comparison with published data does not contradict the assignment of the observed multiple signals to certain types of stable sites, taking into account the spectral features of samples that were prepared by thermal deposition and laser ablation in three different inert gases.

Neutron dark matter decays and correlation coefficients of neutron β−-decays

As we have pointed out in (arXiv:1806.10107 [hep-ph]), the existence of neutron dark matter decay modes n→χ+anything, where χ is a dark matter fermion, for the solution of the neutron lifetime problem changes priorities and demands to describe the neutron lifetime τn=888.0(2.0)s, measured in beam experiments and defined by the decay modes n→p+anything, in the Standard Model (SM). The latter requires the axial coupling constant λ to be equal to λ=−1.2690 (arXiv:1806.10107 [hep-ph]). Since such an axial coupling constant is excluded by experimental data reported by the PERKEO II and UCNA Collaborations, the neutron lifetime τn=888.0(2.0)s can be explained only by virtue of interactions beyond the SM, namely, by the Fierz interference term of order b∼−10−2 dependent on scalar and tensor coupling constants. We give a complete analysis of all correlation coefficients of the neutron β−-decays with polarized neutron, taking into account the contributions of scalar and tensor interactions beyond the SM with the Fierz interference term b∼−10−2. We show that the obtained results agree well with contemporary experimental data that does not prevent the neutron with the rate of the decay modes n→p+anything, measured in beam experiments, to have dark matter decay modes n→χ+anything.

Tests of the standard model in neutron β decay with a polarized neutron and electron and an unpolarized proton

We analyse the electron--energy and angular distribution of the neutron beta decay with polarized neutron and electron and unpolarized proton, calculated in Phys. Rev. C 95, 055502 (2017) within the Standard Model (SM), by taking into account the contributions of interactions beyond the SM. After the absorption of vector and axial vector contributions by the axial coupling constant and Cabibbo-Kobayashi-Maskawa (CKM) matrix element (Bhattacharya et al., Phys. Rev. D 85, 054512 (2012) and so on) these are the contributions of scalar and tensor interactions only. The neutron lifetime, correlation coefficients and their averaged values, and asymmetries of the neutron beta decay with polarized neutron and electron are adapted to the analysis of experimental data on searches of contributions of interactions beyond the SM. Using the obtained results we propose some estimates of the values of the scalar and tensor coupling constants of interactions beyond the SM. We use the estimate of the Fierz interference term "b_F = - 0.0028 +/- 0.0026" by Hardy and Towner (Phys. Rev. C 91, 025501 (2015)), the neutron lifetime "tau_n = 880.2(1.0)s"(Particle Data Group, Chin. Phys. C 40, 100001 (2016)) and the experimental data "N_{\exp} = 0.067 +/- 0.011_{\rm stat.} +/- 0.004_{\rm syst.}" for the averaged value of the correlation coefficient of the neutron-electron spin-spin correlations, measured by Kozela et al. (Phys. Ref. C 85, 045501 (2012)). The contributions of G-odd correlations are calculated and found at the level of 10^{-5} in agreement with the results obtained by Gardner and Plaster (Phys. Rev. C 87, 065504 (2013)).

The \u03c1-meson light-cone distribution amplitudes from lattice QCD

We present the results of a lattice study of the normalization constants and second moments of the light-cone distribution amplitudes of longitudinally and transversely polarized ρ mesons. The calculation is performed using two flavors of dynamical clover fermions at lattice spacings between 0.060 fm and 0.081 fm, different lattice volumes up to mπL = 6.7 and pion masses down to mπ = 150 MeV. Bare lattice results are renormalized non-perturbatively using a variant of the RI′-MOM scheme and converted to the overline{mathrm{MS}} scheme. The necessary conversion coefficients, which are not available in the literature, are calculated. The chiral extrapolation for the relevant decay constants is worked out in detail. We obtain for the ratio of the tensor and vector coupling constants fρT/fρ = 0.629(8) and the values of the second Gegenbauer moments a2‖ = 0.132(27) and a2⊥ = 0.101(22) at the scale μ = 2 GeV for the longitudinally and transversely polarized ρ mesons, respectively. The errors include the statistical uncertainty and estimates of the systematics arising from renormalization. Discretization errors cannot be estimated reliably and are not included. In this calculation the possibility of ρ → ππ decay at the smaller pion masses is not taken into account.

The Microwave Spectrum and Molecular Structure of (E)-1-Chloro-2-Fluoroethylene-HF: Revealing the Balance among Electrostatics, Sterics, and Resonance in Intermolecular Interactions.

The structure of the gas-phase bimolecular complex formed between (E)-1-chloro-2-fluoroethylene and hydrogen fluoride is determined via Fourier transform microwave spectroscopy from 6.9-21.6 GHz. Although the complex adopts a geometry very similar to that of previously studied dihalosubstituted ethylene-HF species, trends observed in the values of structural parameters such as bond lengths, bond angles, and deviations of the primary hydrogen-bonding interaction from linearity provide information regarding the balance among electrostatic, steric, and resonance effects in the structures of these complexes. Consideration of the ab initio interaction potential between (E)-1-chloro-2-fluoroethylene and hydrogen fluoride suggests that it is the strength of the intermolecular bond formed between the hydrogen atom of HF and the fluorine atom of the substituted ethylene that plays the significant role in determining the geometry. In addition to determining the complete nuclear quadrupole coupling constant tensor for the (E)-1-chloro-2-fluoroethylene-HF complex, the corresponding tensor for (E)-1-chloro-2-fluoroethylene itself was measured with greater precision than previously availabe, including the first reported determination of the single, nonzero off-diagonal element, χab.

Uses of tensor-induced spin–orbit splitting to locate spherical doubly-magic SHE

Using optimized iso-scalar and iso-vector tensor coupling constants in Skyrme Hartree–Fock calculation which reproduces the splitting of spin–orbit partners 1f7/2–1f5/2 in 40,48Ca and 56Ni, the evolution of shells in the nuclear chart have been studied through developments in spin–orbit splitting. Signatures for all the magic numbers have been generated without any exception. The procedure when extended to superheavy region indicates the element with Z = 114 and N = 184 to be a doubly-magic spherical nucleus.

VIVO Versus VIV Complex Formation by Tridentate (O, Narom, O) Ligands: Prediction of Geometry, EPR 51V Hyperfine Coupling Constants, and UV–Vis Spectra

Systems formed using the V(IV)O(2+) ion with tridentate ligands containing a (O, N(arom), O) donor set were described. Examined ligands were 3,5-bis(2-hydroxyphenyl)-1-phenyl-1H-1,2,4-triazole (H2hyph(Ph)), 4-[3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazol-1-yl]benzoic acid (H3hyph(C)), 4-[3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazol-1-yl]benzenesulfonic acid (H3hyph(S)), and 2,6-bis(2-hydroxyphenyl)pyridine (H2bhpp), with H3hyph(C) being an orally active iron chelator that is commercially available under the name Exjade (Novartis) for treatment of chronic iron overload arising from blood transfusions. The systems were studied using EPR, UV-Vis, and IR spectroscopies, pH potentiometry, and DFT methods. The ligands bind vanadium with the two terminal deprotonated phenol groups and the central aromatic nitrogen to give six-membered chelate rings. In aqueous solution the main species were the mono- and bis-chelated V(IV)O complexes, whereas in the solid state neutral non-oxido V(IV) compounds were formed. [V(hyph(Ph))2] and [V(bhpp)2] are hexacoordinated, with a geometry close to the octahedral and a meridional arrangement of the ligands. DFT calculations allow distinguishing V(IV)O and V(IV) species and predicting their structure, the (51)V hyperfine coupling constant tensor A, and the electronic absorption spectra. Finally, EPR spectra of several non-oxido V(IV) species were compared using relevant geometrical parameters to demonstrate that in the case of tridentate ligands the (51)V hyperfine coupling constant is related to the geometric isomerism (meridional or facial) rather than the twist angle Φ, which measures the distortion of the hexacoordinated structure toward a trigonal prism.

Tensor Effects in Dipole Excitations at Finite Temperature

Tensor e ects in the dipole excitation of neutron-rich Ni nucleus are investigated in the framework of Skyrme Hartree Fock plus random phase approximation at nite temperature. We calculate isovector giant and pygmy dipole strengths with nite temperature random phase approximation by using di erent tensor correlations. The e ect of both tensor and nite temperature on the giant dipole resonance pygmy dipole resonance energy region is analysed. Pygmy dipole resonance calculations with di erent proton neutron tensor coupling constants are also compared with the experimental results.

Vector and Tensor Coupling Constants of SU(3) Baryons in a Chiral Soliton Model

We report in the present talk a recent investigation on the vector properties of SU(3) baryons, based on a chiral soliton model. All relevant parameters from the model are adjusted to the experimental data of the masses and magnetic moments of the baryon octet. We compute the electromagnetic transitions for the baryon octet, the decuplet, and the antidecuplet. The numerical predictions for transition magnetic moments and radiative partial decay widths are in a very good agreement with all data of existing experiment and the vector meson dominance being used, the coupling constants for the vector mesons and antidecuplet baryon vertices are determined from the calculated transition magnetic moments.

Tensor part of the Skyrme energy density functional. III. Time-odd terms at high spin

This article extends previous studies on the effect of tensor terms in the Skyrme energy density functional by breaking of time-reversal invariance. We have systematically probed the impact of tensor terms on properties of superdeformed rotational bands calculated within the cranked Hartree-Fock-Bogoliubov approach for different parameterizations covering a wide range of values for the isoscalar and isovector tensor coupling constants. We analyze in detail the contribution of the tensor terms to the energies and dynamical moments of inertia and study their impact on quasi-particle spectra. Special attention is devoted to the time-odd tensor terms, the effect of variations of their coupling constants and finite-size instabilities.

TENSOR EFFECTS IN PYGMY DIPOLE EXCITATION

We investigate tensor effects in pygmy dipole excitations for the case of neutron-rich nuclei 68 Ni and 124 Sn using effective nucleon–nucleon Skyrme interaction. We use the Hartree–Fock–Bogoliubov (HFB) theory and employ the quasiparticle random phase approximation (QRPA). We calculate and compare the PDR and also GDR strength in the PDR–GDR energy region for QRPA calculations with and without tensor correlations. The most obvious results for the dipole excitations calculations are strongly dependent on the tensor terms. We see that the tensor correlations are more active at around 14–20 MeV , especially for the neutron-rich nuclei 68 Ni . We also compare the PDR calculations with their experimental results for the different proton–neutron tensor coupling constants.

Possible Mass Enhancement by Multipole Fluctuations Excited via the Singlet–Triplet Crystal Electric Field States in PrOs4Sb12: Sb-NMR Studies Using a Single Crystal

121,123 Sb nuclear magnetic resonance (NMR) measurements of a high-quality single crystalline PrOs 4 Sb 12 have been carried out in magnetic fields up to 98 kOe and in the temperature range of 0.4–30 K. From the analysis of the 121 Sb Knight shift ( K ) and magnetic susceptibility at H ≈90 kOe, the transferred hyperfine coupling constants ( A THF ) are obtained. The Sb isotropic hyperfine coupling constant and anisotropic hyperfine coupling tensor are determined as ≈27.6 Oe/µ B and ≈(149.9,42.3,-192.2) Oe/µ B , respectively. The anisotropic part originates from the spin–dipolar field due to the local spin density at Sb 5 p orbital transferred through the hybridization with 4 f electrons. The results are consistent with the Sb 12 5 p molecular orbital with a u symmetry predicted from the band structure calculation. A THF for H ∥[001] is dependent on the magnetic field, suggesting the coupling of the Sb nuclear dipole moment with not only dipole moments but also octupole moments of the Pr 4 f electrons with the same time reversal. The NMR relaxation rate depends both on magnetic field and temperature, and the temperature dependence of 1/ T 1 is explained by the phenomenological expression 1/( T 1 T A THF 2 )∝(1/ T ) exp [-Δ NMR ( H )/ T ] with excitation gap Δ NMR ( H ). Here, we found that Δ NMR ( H ) is proportional to the largest excitation gap between Γ 1 and Γ t - of the triplet Γ 4 (2) state under the magnetic field. These results indicate that the crystal electric field (CEF) excitation and the degeneracy of the triplet state are important for understanding Sb-NMR results. It is strongly indicated that the mass enhancement in PrOs 4 Sb 12 is caused by the scattering conduction electrons with multipole fluctuations via the singlet–triplet CEF excitation.

Calculating the Response of NMR Shielding Tensor σ(31P) and 2J(31P,13C) Coupling Constants in Nucleic Acid Phosphate to Coordination of the Mg2+ Cation

Dependence of NMR (31)P shielding tensor and (2)J(P,C) coupling constants on solvation of nucleic acid phosphate by Mg(2+) and water was studied using methods of bioinformatic structural analyses of crystallographic data and DFT B3LYP calculations of NMR parameters. The effect of solvent dynamics on NMR parameters was calculated using molecular dynamic. The NMR calculations for representative solvation patterns determined in crystals of B-DNA and A-RNA molecules pointed out the crucial importance of local Mg(2+) coordination geometry, including hydration by explicit water molecules and necessity of dynamical averaging over the solvent reorientation. The dynamically averaged (31)P chemical shift decreased by 2-9.5 ppm upon Mg(2+) coordination, the chemical shielding anisotropy increased by 0-20 ppm, and the (2)J(P,C5') coupling magnitude decreased by 0.2-1.8 Hz upon Mg(2+) coordination. The calculated decrease of the (31)P chemical shift is in excellent agreement with the 1.5-10 ppm decrease of the phosphorothioate (31)P chemical shift upon Cd(2+) coordination probed experimentally in hammerhead ribozyme (Suzumura; et al. J. Am. Chem. Soc. 2002, 124, 8230-8236; Osborne; et al., Biochemistry 2009, 48, 10654-10664). None of the dynamically averaged NMR parameters unequivocally distinguishes the site-specific Mg(2+) coordination to one of the two nonesterified phosphate oxygen atoms of the phosphate determined by bioinformatic analyses. By comparing the limit cases of static and dynamically averaged solvation, we propose that mobility of the solvent has a dramatic impact on NMR parameters of nucleic acid phosphate and must be taken into account for their accurate modeling.

BAYESIAN MODEL SELECTION FOR ELECTROMAGNETIC KAON PRODUCTION ON THE NUCLEON

We present the results of a Bayesian analysis of a Regge model for K+Λ photoproduction. The model is based on the exchange of K+(494) and K*+(892) trajectories in the t-channel. For different prior widths, we find decisive Bayesian evidence (Δ ln Ƶ ≈ 24) for a K+Λ photoproduction Regge model with a positive vector coupling and a negative tensor coupling constant for the K*+(892) trajectory, and a rotating phase factor for both trajectories. Using the χ2 minimization method, one could not draw this conclusion from the same dataset.

Bayesian model selection for electromagnetic kaon production on the nucleon

We present the results of a Bayesian analysis of a Regge model to describe the background contribution for K+Λ and K+Σ0 photoproduction. The model is based on the exchange of K+(494) and K*+(892) trajectories in the t-channel. We utilise the Bayesian evidence Z to determine the best model variant for each channel. The Bayesian evidence integrals were calculated using the Nested Sampling algorithm. For different prior widths, we find decisive Bayesian evidence (ΔlnZ≈24) for a K+Λ photoproduction Regge model with a positive vector coupling and a negative tensor coupling constant for the K*+(892) trajectory, and a rotating phase factor for both trajectories. Using the χ2 minimisation method, one could not draw this conclusion from the same dataset. For the K+Σ0 photoproduction Regge model, on the other hand, the difference between the evidence integrals is insufficient to pinpoint one model variant.

Global nuclear structure effects of the tensor interaction

A direct fit of the isoscalar spin-orbit (SO) and both isoscalar and isovector tensor coupling constants to the f(5/2)-f(7/2) SO splittings in Ca-40, Ni-56, and Ca-48 nuclei requires a drastic redu ...

An experiment to measure the bound-β- decay of the free neutron

The two-body neutron β-decay into a hydrogen atom and an electron antineutrino is investigated. The hyperfine-state population of the monoenergetic hydrogen atoms (326.5 eV) yields the neutrino left-handedness or a possible right-handed admixture and possible small scalar and tensor contributions to the weak force. The constraints on the neutrino helicity and the scalar and tensor coupling constants of weak interaction can be improved considerably.

GLOBAL NUCLEAR STRUCTURE ASPECTS OF TENSOR INTERACTION

A direct fit of the isoscalar spin-orbit and both isoscalar and isovector tensor coupling constants to the f5/2 - f7/2 SO splittings in 40 Ca , 56 Ni , and 48 Ca requires (i) a significant reduction of the standard isoscalar spin-orbit strength and (ii) strong attractive tensor coupling constants. The aim of this paper is to address the consequences of these strong attractive tensor and weak spin-orbit fields on total binding energies, two-neutron separation energies and nuclear deformability.

VECTOR AND AXIAL-VECTOR STRUCTURES OF THE Θ+

We present in this talk recent results of the vector and axial-vector transitions of the nucleon to the pentaquark baryon Θ+, based on the SU(3) chiral quark-soliton model. The results are summarized as follows: K*NΘ vector and tensor coupling constants turn out to be gK*NΘ ≃ 0.81 and fK*NΘ ≃ 0.84, respectively, and the KNΘ axial-vector coupling constant to be [Formula: see text]. As a result, the total decay width for Θ+ → NK becomes very small: ΓΘ→NK ≃ 0.71 MeV , which is consistent with the DIANA result ΓΘ→NK = 0.36 ± 0.11 MeV .