Cubic harmonic analysis of magnetic anisotropy measurements on single crystal HoxTb1−xFe2 laves phase compounds

Room temperature magnetic anisotropy measurements have been made on a series of low anisotropy Ho_xTb_1?xFe₂ compounds, with 0.826 < x < 0.908, using torque magnetometry techniques. An analysis of the data using the conventional expansion of anisotropy energy in terms of the direction cosines proved inadequate because of the presence of higher order contributions to the anisotropy. When these contributions were included in the expansion, non unique anisotropy constants were obtained which were not consistent with the predictions of the single ion model. An analysis of the data using an expansion of the anisotropy in terms of an orthonormal set of functions, namely the cubic harmonics developed by Mueller and Priestly, proved more successful. The results showed that the two lowest order anisotropy constants, κ₄ and κ₆, both varied linearly with holmium concentrations as predicted by the single ion model; however, κ₈, the next higher order term, was not consistent with the predicted behavior. The origin of this contribution is believed to be related to the magnetostriction.     

Three-body force and the tetraquark interpretation of light scalar mesons

We study the possible tetraquark interpretation of light scalar meson states a0(980), f0(980), κ,σ within the framework of the non-relativistic potential model. The wave functions of tetraquark states are obtained in a space spanned by multiple Gaussian functions. We find that the mass spectra of the light scalar mesons can be well accommodated in the tetraquark picture if we introduce a three-body quark interaction in the quark model. Using the obtained multiple Gaussian wave functions, the decay constants of tetraquarks are also calculated within the "fall apart" mechanism.     

Non-Perturbative Propagators in QCD

We have derived the gluon and quark complete propagators under chain approximation in the presence of gluon condensation <Ω│G²│Ω> and quark condensation <Ω│ψψ│Ω>.The nonvanishing vacuum average value for gluon composite operator <Ω│Aαμ(x)Abv(y)│Ω> is expanded into a series in terms of two point distance (x—y) in Lorentz gauge condition.The series is of translation invariance as compared with the series in fixed gauge condition.<Ω│G²│Ω> is introduced as the series coefficient when we take into account the correction of <Ω│Aαμ(x)Abv(y)│Ω> to quark propagator.     

Investigation of quark distributions in a family of pentaquarks using the Thomas-Fermi quark model

Using the Thomas-Fermi quark model,a collective,spherically symmetric density of states is created to represent a gas of interacting fermions with various degeneracies at zero temperature.Over a family of pentaquarks,uudcc,color interaction probabilities were obtained after averaging over all the possible configurations.Three different functions are developed for light,charm,and anti-charm quarks and are assumed to be linearly related by some proportionality constants.Interesting patterns of quark distributions are observed while analyzing the quark function consistency conditions for such constants.     

On a Class of World Surfaces for the Linear String Model of a Baryon

For the linear string model of a baryon where three material points (three quarks) are connected in series by relativistic strings, a class of physically realizable world surfaces has been found which admit parametrization such that the equations of motion and the boundary conditions are linear due to the proportionality of the parameter associated with the quark trajectories to the natural parameter. The surfaces of this class are represented as a Fourier series of the eigenfunctions of some boundary-value problem. It is shown that the series generating such surfaces contains a finite number of terms. In particular, in the 3+1-dimensional Minkowski space, one and only one surface of the class under consideration is realizable, namely, the helicoid.     

Calculating the Cabibbo angle

Within a gauge theory based on the gauge group SU₂ × SU₂ × U₁ and on the four quark flavours u, d, s, and c the Cabibbo angle is calculated in terms of the quark mass ratios. The u and d quark masses are zero in the absence of weak interaction mixing due to the existence of a discrete symmetry R. The calculated value of the Cabibbo angle is in agreement with the observed value.     

Exclusive electroproduction and the quark structure of the nucleon

The natural interpretation of deep inelastic scattering is in terms of hard scattering on QCD constituents of the target. We examine the relation between amplitudes measured in exclusive lepto-production and the quark content of the nucleon. We show that in the Bjorken limit, the natural interpretation of amplitudes measured in these hard exclusive processes is in terms of the quark content of the meson cloud and not the target itself. In this limit, the most efficient representation of these exclusive processes is in terms of leading Regge amplitudes.     

Axial charges of N (1535) and N (1650) in two-flavor lattice QCD

We show the lattice QCD results on the axial charge g~(N~*N~*)_A of negative parity nucleon resonances, N~*(1535) and N~*(1650), which are key clues to the chiral structure in baryon sector. The measurements are performed with up and down dynamical quarks employing the renormalization-group improved gauge action at β=1.95 and the ο(a) improved clover quark action with the hopping parameters, κ=0.1375, 0.1390 and 0.1400. In order to properly separate signals of N~*(1535) and N~*(1650), we construct 2×2 correlation matrices and diagonalize them. Wraparound contributions in the correlator, which can be another source of signal contaminations, are eliminated by imposing the Dirichlet boundary condition in the temporal direction. We find that the axial charge of N~* (1535) takes small values as g~(N~*N~*)～ο(0.1), whereas that of N~*(1650) is about 0.5, which is found independent of quark masses and consistent with the predictions by the naive nonrelativistic quark model.     

Long-range intensity correlation and the approach to localization

Abstract

The influence of internal surface reflectivity is incorporated into a heuristic model of long-range intensity correlation. This allows us to identify the spatial intensity correlation function in a sample of randomly positioned polystyrene spheres as the sum of a first-order term in the correlation parameter κ, which falls linearly with detector separation, and a constant term, which is of order κ². κ is a measure of the proximity to the localization threshold. In a sample which is a mixture of metallic and dielectric spheres and in which κ becomes large, the probability of large intensity fluctuations increases. The distribution of intensities is then found to be stretched exponential even for sample lengths which are comparable to the wavelength of the radiation.     

Cabibbo current and CP violation in a six quark gauge model

The extended Cabibbo current with CP-violation in a six quark gauge model is obtained in terms of quark mass ratios and phases in the quark mass matrices. The model predicts a long-lived heavy quark and its selection rule.     

QCD非微扰和能量丢失效应对夸克分布影响

在非常数性K因子的情况下,根据核Drell-Yan过程的高能强子h同原子核A碰撞和高能轻子l同原子核A深度非弹性碰撞的实验数据,在考虑QCD非微扰效应对深度非弹性散射部分子分布的影响及Drell-Yan过程中的能量丢失效应,计算确定价夸克分布和海夸克分布核效应函数RAυ(x₂),RAS(x₂)的变化,深化了对原子核内夸克分布受核效应影响的认识     

Flux confinement in the leading logarithm model

We study the statics of quasi-abelian quark and antiquark source charges in the approximation in which leading logarithm radiative corrections are retained in the gauge gluon effective action functional. We show that the partial differential equation for the flux function is of degenerating elliptic type, leading to flux confinement within a free boundary which is a characteristic. The static potential increases linearly for large source separations, with a logarithmic subdominant term.     

Minimally doubled fermions at one loop

Minimally doubled fermions have been proposed as a cost-effective realization of chiral symmetry at non-zero lattice spacing. Using lattice perturbation theory at one loop, we study their renormalization properties. Specifically, we investigate the consequences of the breaking of hyper-cubic symmetry, which is a typical feature of this class of fermionic discretizations. Our results for the quark self-energy indicate that the four-momentum undergoes a renormalization which is linearly divergent. We also compute renormalization factors for quark bilinears, construct the conserved vector and axial-vector currents and verify that at one loop the renormalization factors of the latter are equal to one.     

Electromagnetic mass shift of pions in unified gauge field theories and the light-cone

The electromagnetic mass shift of pions is discussed in unified gauge field theories of weak and electromagnetic interactions to second order of the electric charge and the pion mass, respectively. We calculate the contributions of the next to leading light-cone singularities (quark mass terms) and it is found that these do not contribute to the divergences in the mass shift provided the masses of the bare proton quark and neutron quark are equal. γ, Z, W, φ exchanges are taken into account. Different bare quark masses in general make the mass shift divergent. In the tadpole contribution, the Born term causes a divergence unless we extrapolate first to q² = 0.     

Minimal subtraction and the decoupling of heavy quarks for arbitrary values of the gauge parameter

The decoupling of a heavy quark is investigated to two loops for QCD renormalized by minimal subtraction. It is shown that the heavy quark effects can be absorbed into an effective coupling constant, an effective gauge parameter and effective masses for the light quarks. The relations between these effective parameters and the parameters of the full theory are gauge invariant. In terms of the effective parameters the theory satisfies renormalization group equations which refer only to the light degrees of freedom.     

Gauge-invariant formalism and quark confinement in QCD2

New gauge-invariant vector and spinor fields are introduced. Gauge-invariant quark propagator is defined in terms of these new fields. The equation for such a propagator, taken in 1/N approximation, does not require the introduction of an infrared regularization. As the regularization parameter in our approach there stands such a parameter which limit value corresponds to the gauge-invariant fields and translationally invariant quark propagator. It is shown that in this limit the pole of the gauge-invariant quark propagator shifts towards infinity what is usually treated as the confinement of a single quark.     

Wave,particle-family duality and the conservation of discrete symmetries in strong interaction

This paper starts from a nonlinear fermion field equation of motion with a strongly coupled self-interaction. Nonperturbative quark solutions of the equation of motion are constructed in terms of a Reggeized infinite component free spinor field. Such a field carries a family of strongly interacting unstable compounds lying on a Regge locus in the analytically continued quark spin. Such a quark field is naturally confined and also possesses the property of asymptotic freedom. Furthermore, the particular field self-regularizes the interactions and naturally breaks the chiral invariance of the equation of motion. We show why and how the existence of such a strongly coupled solution and its particle-family, wave duality forces a change in the field equation of motion such that it conserves C, P, T, although its individual interaction terms are of V-A and thus C, P nonconserving type.Deceased.     

The SU(3) dibaryons in the chiral quark soliton model

In this Letter we investigate an SU(3) extension of the axially symmetric B=2 chiral quark soliton model. The classical soliton is extended to the SU(3) by trivial embedding. We expand the quark determinant in terms of the collective angular velocity up to the second order and the quark mass difference of the first order. The mass spectrum and the binding energy of the baryon–baryon channels down to strangeness S=−6 are then obtained.     

Exclusive photoproduction of hard dijets and magnetic susceptibility of the QCD vacuum

We argue that coherent production of hard dijets by linearly polarized real photons can provide direct evidence for chirality violation in hard processes, the first measurement of the magnetic susceptibility of the quark condensate and the photon distribution amplitude. It can also serve as a sensitive probe of the generalized gluon parton distribution. Numerical calculations are presented for HERA kinematics.     

Phenomenological description of relativistic-quark interaction on the basis of the Dirac equation with the Cornell potential

Relativistic-quark interaction is described phenomenologically on the basis of the Dirac equation with the Cornell potential. A general form of the initial equation involving the vector and scalar components of the Cornell potential is used for the case of an arbitrary relation between them. The Hamiltonian in the Foldy–Wouthuysen representation is derived in a general form with allowance for electromagnetic interaction. In contrast to earlier investigations, it is relativistic and exact for the zeroth- and first-order terms in the Planck constant and also for those second-order terms that describe contact interactions. General quantum-mechanical equations of motion for the momentum and spin are derived, and the classical limit of the Hamiltonian and for the equations of motion is found for the first time. A relation between the angular velocity of quark spin precession and the force acting on the quark is obtained. The energy of spin–orbit interaction is rather high (on the order of 100 MeV). Terms that describe spin–orbit and contact interactions have opposite signs for the vector and scalar components of the Cornell potential. The evolution of the quark helicity and the spin–spin interaction of the quarks are also calculated.