Tensor Coupling Constants Research Articles

Vector transition form factors of the [formula omitted] and [formula omitted] in the [formula omitted] chiral quark–soliton model

We investigate the vector transition form factors of the nucleon and vector meson K ∗ to the pentaquark baryon Θ + within the framework of the SU ( 3 ) chiral quark–soliton model. We take into account the rotational 1 / N c and linear m s corrections, assuming isospin symmetry and employing the symmetry-conserving quantization. It turns out that the leading-order contributions to the form factors are almost cancelled by the rotational corrections. Because of this, the flavor SU ( 3 ) symmetry-breaking terms yield sizeable effects on the vector transition form factors. In particular, the main contribution to the electric-like transition form factor comes from the wave-function corrections, which is a consequence of the generalized Ademollo–Gatto theorem derived in the present work. We estimate with the help of the vector meson dominance the K ∗ vector and tensor coupling constants for the Θ + : g K ∗ N Θ = 0.74 – 0.87 and f K ∗ N Θ = 0.53 – 1.16 . We argue that the outcome of the present work is consistent with the null results of the CLAS experiments in the reactions γ n → K − Θ + and γ p → K ¯ 0 Θ + . The results of the present work are also consistent with the recent experiments at KEK. In addition, we present the results of the Σ 10 ¯ → N K ¯ ∗ transition form factors and its K ¯ ∗ N Σ 10 ¯ coupling constants.

Spin-orbit and tensor mean-field effects on spin-orbit splitting including self-consistent core polarizations

A new strategy of fitting the coupling constants of the nuclear energy density functional is proposed, which shifts attention from ground-state bulk to single-particle properties. The latter are analyzed in terms of the bare single-particle energies and mass, shape, and spin core-polarization effects. Fit of the isoscalar spin-orbit and both isoscalar and isovector tensor coupling constants directly to the ${f}_{5/2}\text{\ensuremath{-}}{f}_{7/2}$ spin-orbit splittings in $^{40}\mathrm{Ca}$, $^{56}\mathrm{Ni}$, and $^{48}\mathrm{Ca}$ is proposed as a practical realization of this new program. It is shown that this fit requires drastic changes in the isoscalar spin-orbit strength and the tensor coupling constants as compared to the commonly accepted values, but it considerably and systematically improves basic single-particle properties including spin-orbit splittings and magic-gap energies. Impact of these changes on nuclear binding energies is also discussed.

Dispersion analysis of the nucleon form factors including meson continua

Dispersion relations provide a powerful tool to analyze the electromagnetic form factors of the nucleon for all momentum transfers. Constraints from meson-nucleon scattering data, unitarity, and perturbative quantum chromodynamics (QCD) can be included in a straightforward way. In particular, we include the $2\ensuremath{\pi},\ensuremath{\rho}\ensuremath{\pi}$, and $K\overline{K}$ continua as independent input in our analysis and provide an error band for our results. Moreover, we discuss two different methods to include the asymptotic constraints from perturbative QCD. We simultaneously analyze the world data for all four form factors in both the spacelike and timelike regions and generally find good agreement with the data. We also extract the nucleon radii and the $\ensuremath{\omega}\mathit{NN}$ coupling constants. For the radii, we generally find good agreement with other determinations with the exception of the electric charge radius of the proton, which comes out smaller. The $\ensuremath{\omega}\mathit{NN}$ vector coupling constant is determined relatively well by the fits, but for the tensor coupling constant even the sign cannot be determined.

A local non-Abelian gauge invariant action stemming from the nonlocal operator FmuN(D²)-1FmuN

We report on the nonlocal gauge invariant operator of dimension two, FµN (D²)-1 FµN. We are able to localize this operator by introducing a suitable set of (anti)commuting antisymmetric tensor fields. Starting from this, we succeed in constructing a local gauge invariant action containing a mass parameter, and we prove the renormalizability to all orders of perturbation theory of this action in the linear covariant gauges using the algebraic renormalization technique. We point out the existence of a nilpotent BRST symmetry. Despite the additional (anti)commuting tensor fields and coupling constants, we prove that our model in the limit of vanishing mass is equivalent with ordinary massless Yang-Mills theories by making use of an extra symmetry in the massless case. We also present explicit renormalization group functions at two loop order in the ${\overline{\mbox{MS}}}$ scheme.

Phonon–phason coupling in decagonal quasicrystals

Phonon–phason coupling in decagonal quasicrystals has been discussed in terms of phonon strains induced in crystal approximants. Elastically, decagonal quasicrystals can be classified into two groups having different symmetries in the coupling constant tensor; one has only one independent coupling constant, K 4, and the other has two such constants, K 4 and K 5. It has been shown that the orthorhombic and monoclinic approximants formed in various alloy systems can be interpreted as resulting from the two different types of decagonal quasicrystals and that a slight distortion in the unit cell of the monoclinic phases is attributable to the effect of one of the coupling constants, K 5. Phonon strains induced in monoclinic approximants of the Al–Co system have been calculated from their lattice constants and the coupling constants K 4 and K 5 have been evaluated.

An experiment for the measurement of the bound- β-decay of the free neutron

The hyperfine-state population of hydrogen after the bound-beta decay of the neutron directly yields the neutrino left-handedness or a possible right-handed admixture and possible small scalar and tensor contributions to the weak force. Using the through-going beam tube of a high-flux reactor, a background free hydrogen rate of ca. 3 s$^{-1}$ can be obtained. The detection of the neutral hydrogen atoms and the analysis of the hyperfine states is accomplished by Lamb shift source type quenching and subsequent ionization. The constraints on the neutrino helicity and the scalar and tensor coupling constants of weak interaction can be improved by a factor of ten.

Quantum properties of a non-Abelian gauge invariant action with a mass parameter

We continue the study of a local, gauge invariant Yang-Mills action containing a mass parameter, which we constructed in a previous paper starting from the nonlocal gauge invariant mass dimension two operator ${F}_{\ensuremath{\mu}\ensuremath{\nu}}({D}^{2}{)}^{\ensuremath{-}1}{F}_{\ensuremath{\mu}\ensuremath{\nu}}$. We return briefly to the renormalizability of the model, which can be proven to all orders of perturbation theory by embedding it in a more general model with a larger symmetry content. We point out the existence of a nilpotent Becchi-Rouet-Stora-Tyutin (BRST) symmetry. Although our action contains extra (anti)commuting tensor fields and coupling constants, we prove that our model in the limit of vanishing mass is equivalent with ordinary massless Yang-Mills theories. The full theory is renormalized explicitly at two loops in the $\overline{\mathrm{MS}}$ scheme and all the renormalization group functions are presented. We end with some comments on the potential relevance of this gauge model for the issue of a dynamical gluon mass generation.

General classification and analysis of neutronβ-decay experiments

A method for the general analysis of the sensitivities of neutron beta-decay experiments to manifestations of possible deviations from the Standard model is proposed. In a consistent fashion, we take into account all known (radiative and recoil) corrections which are incorporated within the Standard Model to provide a description of angular correlations in neutron decay in the first order of approximation, or down to the level of $\sim 10^{-5}$. The contributions from models beyond the Standard model are, for low energy neutron decay, parameterized in terms of vector, axial-vector, scalar and tensor coupling constants and in terms of parameters related to specific models. For the present analysis we derive the exact expressions for the neutron beta decay probability which includes all possible manifestations models beyond the Standard Model down to level of $\sim 10^{-5}$ without time-reversal violation. Based on the general expressions for manifestation of the deviations from the standard model, we present analysis of the sensitivities for selected neutron decay experiments.

Associative photoproduction of Roper resonance and ω meson

Associative photoproduction of $\ensuremath{\omega}$ meson and ${N}^{*}(1440)$ on nucleons, $\ensuremath{\gamma}+\stackrel{\ensuremath{\rightarrow}}{N}\ensuremath{\omega}{+N}^{*}(1440),$ in the near threshold region is investigated in a framework employing effective Lagrangians. Besides $\ensuremath{\pi}$ exchange in the t channel, baryon exchanges, i.e., N and ${N}^{*}$ exchanges, in the s and u channels are also taken into account in calculations of differential cross section and beam asymmetry. Important inputs of this model are the vector and tensor coupling constants of $\ensuremath{\omega}{\mathrm{NN}}^{*}(1440)$ vertex, which are assumed to be equal to the values of these couplings for $\ensuremath{\omega}\mathrm{NN}$ vertex. Using our previous estimation of $\ensuremath{\omega}\mathrm{NN}$ coupling constants obtained from a fit to available experimental data on photoproduction of $\ensuremath{\omega}$ meson in the near threshold region, we produce the necessary numerical predictions for different observables in $\ensuremath{\gamma}+\stackrel{\ensuremath{\rightarrow}}{N}\ensuremath{\omega}{+N}^{*}(1440).$ Numerical results show that at low $|t|$ dominant contribution comes from t channel $\ensuremath{\pi}$ exchange while the effects of nucleon and ${N}^{*}(1440)$ pole terms can be seen at large $|t|.$ Our predictions for the differential cross section and beam asymmetry for the processes $\ensuremath{\gamma}+\stackrel{\ensuremath{\rightarrow}}{N}\ensuremath{\omega}{+N}^{*}(1440),$ where N is proton and neutron, at ${E}_{\ensuremath{\gamma}}=2.5\mathrm{GeV}$ are presented with zero width approximation and also with the inclusion of width effects of ${N}^{*}(1440).$

Modified Derivative Scalar Coupling Model in Semi-infinite Nuclear Matter**The project supported in part by National Natural Science Foundation of China, and Major State Basic Research Developing Program with Grant No. G2000077400

Semi-infinite nuclear matter has been investigated in relativistic Thomas–Fermi and Hartree approximations based on the modified derivative scalar coupling model. Our results show that the spin-orbit potential has been improved by the tensor coupling. However, the surface tension and the surface thickness become considerably small with increasing of the tensor coupling constant. The effects of the -meson mass on the spin-orbit potential, on the surface tension, and on the surface thickness have also been discussed.

An investigation of the Lorentz structure in tau decays

This paper describes a measurement of the Michel parameters, η, ϱ, Ξ, Ξδ, the average ν τ helicity, h ν τ , and the anomolous tensor coupling constant, κ τ W , in τ lepton decays using the DELPHI detector. The τ + τ − pairs were produced at the LEP e + e − collider at CERN between 1992 and 1995. The Michel parameters, together with a measurement of the τ polarisation, P τ, were extracted in a simultaneous fit to the two dimensional momentum spectra of leptonic and semi-leptonic τ decays. The anomalous tensor coupling constant, κ τ W , was measured using the same selected data.

Measurement of the Energy Spectrum ofνefrom Muon Decay and Implications for the Lorentz Structure of the Weak Interaction

The KARMEN experiment uses the reaction 12C(\nu_e,e-)12N to measure the energy distribution of \nu_e emitted in muon decay at rest. The \nu_e analog \omega_l of the famous Michel parameter \rho has been derived from a maximum-likelihood analysis of events near the kinematic end point, E_max. The result, \omega_l = (2.7^{+3.8}_{-3.3}\pm 3.1) * 10^{-2}, is in good agreement with the standard model prediction \omega_l= 0. We deduce a 90% confidence upper limit of \omega_l <= 0.113, which corresponds to a limit of |g^S_RL + 2 g^T_RL| <= 0.78 on the interference term between scalar and tensor coupling constants.

Meson substructure and the ϱNN and ωNN couplings

Estimates are made of the ϱNN and ωNN vector and tensor coupling constants and form factors by consideration of vector qq correlations as producted by a quark model nucleon source. Attention is paid to the finite extent of the qq correlations and to their departure from true bound state form at space-like momenta.

Hydrogen-bonded structure and NMR parameters of oxygen-17 labeled poly(L-alanine)s as studied by solid state oxygen-17 NMR spectroscopy

17O-labeled poly(L-alanine)s with different degrees of polymerization were synthesized. These poly(L-alanine)s take an α-helix form and a β-sheet form. Solid state 17O NMR spectra of these polymers were measured at different frequencies. By comparing the obtained spectrum and theoretical simulation, the NMR parameters, such as the quadrupolar coupling constant and chemical shift tensor components, were determined. The relationship between the hydrogen-bonded structure and the NMR parameters was elucidated in relation to the main-chain conformation. In addition, these results were compared with those of polyglycine as reported previously, and the feature of 17O NMR behavior of these polypeptides, associated with the hydrogen-bonded structure, was discussed.

Nmr Study in Sodium-Hydrogen-C60 Superconductor

ABSTRACT23Na and 1H NMR studies have been carried out for a NaxHyC60 superconductor The peak position of the 23Na NMR spectrum exhibits discontinuous upfield shift of 30 ppm at about 250 K, indicates a first order phase transition From the line shape of the 23Na spectrum obtained at 7 K, the quadrupole coupling constant tensor is evaluated to be |e2Qq/h|=3.7 MHz with the asymmetry parameter η = 0.95. The 1H NMR spectrum suggests an anionic hydrogen state with weakly delocalized nature.

A Method for Improving the Constraint on the Tensor Coupling Constant in Radiative Pion Decay

The possibility exists for improving the present experimental constraint on the tensor coupling constant in radiative pion decay by at least a factor of six. The method emphasizes relative decay probabilities rather than absolute rates.

Microwave spectra of monohalogenated allenes. Chloroallene and iodoallene

The microwave spectra of chloroallene, ClHCCCH2 and ClDCCCH2(35/37Cl), and iodoallene, IHCCCH2 and IDCCCH2, have been studied from 7 to 40 GHz. A least-squares analysis of the observed a- and b-type transition frequencies gave rotational constants and components of the halogen nuclear quadrupole coupling constant tensor in the principal axes systems. The structural parameters for chloroallene and iodoallene are calculated from the rotational constants. The C—X bond lengths in chloroallene and iodoallene were found to be a little longer than those in chloroethene and iodoethene, respectively, in accordance with a slightly lower π character for the carbon–halogen bonds in the haloallenes than those in the haloethenes.

Microwave spectrum, structure, internal rotation, and nuclear quadrupole coupling constant tensor of acetyl chloride

The microwave spectra of acetyl chloride and its 11 isotopic species were measured. A least-squares analysis of the observed frequencies gave the rotational, quartic centrifugal distortion constants, the diagonal components of the nuclear quadrupole coupling constant tensor χ, the barrier to methyl internal rotation, and the direction cosines of the internal rotation axis in the inertial axes system, simultaneously. The r s structure was well established from the moments of inertia calculated from the observed rotational constants. The molecular structure of acetyl chloride was compared with those of analogous molecules.

Microwave Spectrum, Structure, and Nuclear Quadrupole Coupling Constant Tensor of Iodomethyl Methyl Ether

Microwave spectra of iodomethyl methyl ether and its 10 isotopic species have been measured. A least-squares analysis of the observed frequencies gave rotational and quartic centrifugal distortion constants and all the components of the nuclear quadrupole coupling constant tensor. The rs structure has been well established from the moments of inertia calculated from the observed rotational constants. The observed nuclear quadrupole coupling constant tensor in the inertial principal axes system could be transformed into that in its own principal axes system. The directions of the χ principal axes in the molecule were found to be closely related to the signs of three off-diagonal χ components in the inertial principal axes system which could not be determined by the least-squares fit of the observed frequencies. The signs of the three off-diagonal χ components were concluded to be (+, +, −) for χab, χac, and χbc, respectively. The z axis of the principal χ system is roughly along the CI bond, while the x axis is no longer in the OCI plane but is inclined by about 6°30′ toward the side where the CH3 group exists. The molecular structure and nuclear quadrupole coupling constant tensor of the present molecule were compared with those of the other halomethyl ethers, alkyl halides, and alkyl ethers.

ESR Studies of Monosulfide Radicals in Irradiated N-Acetyl-L-cysteine Single Crystals

Electron spin resonance studies of three monosulfide radicals in N-acetyl-L-cysteine single crystals have been performed at 4 K. These radicals are characterized by very large g-tensor anisotropies; one is believed to have the largest g anisotropy ever reported for an organic free radical (1.9 ≤ g ≤ 2.5). Sulfur 3 d-orbital spin density is largely responsible for the unusual g tensor in at least two of these radicals. While these three radicals are almost identical in structure, their ESR parameters, such as g tensor and 33S hyperfine coupling constants, are affected by the environments of the radicals trapped in the crystal structure. Hydrogen bonding to the sulfur atom appears to play an important role.