The quark spin structure of the nucleon

Some non-perturbative aspects of the nucleon quark spin structure are reviewed. The first part is a brief summary of early theoretical developments in the field of polarized deep inelastic scattering of electrons on polarized nucleons and an illustration of the non-perturbative power of lattice QCD 25 years later. The second part is a short pedagogical introduction to the analysis of high energy scattering in the complex angular momentum plane, with particular emphasis on spin-dependent deep inelastic electron-nucleon scattering. The third part comprises a brief introduction to lattice QCD and its applications in the non-perturbative determination of the spin-dependent structure functions.     

Q2 evolution of the neutron spin structure moments using a 3He target

We have measured the spin structure functions g(1) and g(2) of 3He in a double-spin experiment by inclusively scattering polarized electrons at energies ranging from 0.862 to 5.058 GeV off a polarized 3He target at a 15.5 degrees scattering angle. Excitation energies covered the resonance and the onset of the deep inelastic regions. We have determined for the first time the Q2 evolution of Gamma(1)(Q2)= integral (1)(0)g(1)(x,Q2)dx, Gamma(2)(Q2)= integral (1)(0)g(2)(x,Q2)dx, and d(2)(Q2)= integral (1)(0)x(2)[2g(1)(x,Q2)+3g(2)(x,Q2)]dx for the neutron in the range 0.1< or =Q2< or =0.9 GeV2 with good precision. Gamma(1)(Q2) displays a smooth variation from high to low Q2. The Burkhardt-Cottingham sum rule holds within uncertainties and d(2) is nonzero over the measured range.     

磁霍普夫子及其三维自旋动力学研究

磁霍普夫子是一类新兴的三维磁拓扑孤子,具有精妙的三维自旋拓扑结构,可以展现丰富新奇的物理特性。随着最近磁霍普夫子研究的兴起,三维拓扑孤子相关的研究也进入了一个新的阶段。文章将简要介绍如何在固体磁性系统中实现稳定的磁霍普夫子,同时针对一个最简单的霍普夫子自旋结构,讨论其有趣的三维自旋动力学特性,为今后进一步研究霍普夫子和推进三维拓扑自旋电子学的发展抛砖引玉。     

Magnetic resonances in one-dimensional spin systems NENP and NINO

We present Electron-Spin-Resonance experiments in the frequency range 35–420 GHz in magnetic fields up to 14 T and with temperatures down to 1.5 K. The quasi-onedimensionalS=1 Spin Systems NENP and NINO exhibit similar resonance-modes, which can be associated with transitions between excited states atq= and excitations from the groundstate. Groundstateexcitation can be explained with regard to a transverse staggered field due to inequivalent Ni²⁺-sites along the chains. Several features are discussed like polarisation-and temperature dependence of line-intensity and the angular and temperature-dependence of resonance-field.     

Magnetic moments and the proton structure function

The EMC collaboration have reported a measurement of the proton structure function which has been interpreted to mean that the spin of the proton is not predominantly that of the quarks (=u+d+s=0.13±0.19). We show that the magnetic moments of the baryons are independent of this measurement and are given (within 10–20%) for a range of including the valence model value =1. The magnetic moments of the quarks can only be fixed if the quantity is determined very accurately.     

Magnetic moments of the nucleon octet in a relativistic light-cone quark model

The magnetic moments of the baryon octet are calculated in a relativistic constituent quark model formulated in the light-cone Fock approach. Invoking a natural idea of strangeness-dependent hadron size we find very good agreement (to an accuracy of 1σ) for the recent precision hyperon magnetic-moment data and reveal 10–15% discrepancy for the Σ⁻ and nucleon. It suggests pions as a missing ingredient in the baryon magnetic moment calculations.     

Magnetic moments and structure of the nuclei3H,3He and of baryons

From a solution of the problem of magnetic moments of the nuclei³H and³He, two properties are obtained: - These nuclei have mixed orbital ground states. - These states are not charge symmetric. The first property is expected to hold also for baryons in the quark model, on account of recently measured magnetic moments. Supporting evidence and implications for baryon structure are discussed.     

Nucleon spin structure in a relativistic constituent quark model

The spin structure of the nucleon is analyzed using a relativistic constituent quark model in light-front formulation. We investigate, in particular, relativistic effects on the axial vector coupling constants. Electromagnetic and axial form factors are constructed in terms of quark form factors that reflect the possible non-trivial structure of the constituent quarks. We study the influence of flavour mixing effects on axial constants and discuss the extent to which such effects can renormalize the singlet axial constant g _A ⁰ from its SU(6) quark model value.     

Magnetic moments and their interaction in insulating crystals

This article discusses the several contributions to the magnetic moment of an ion in a crystal and how such individual magnetic moments contribute to the total moment of the crystal as a whole. It deals particularly with Co²+ ions in an insulating host, taking MgF₂ as an example. when two Co²+ ions are in close proximity, exchange effects occur and give rise to a change in the magnetic moment of each ion in the pair. This is normally described as a g-shift and its implications in concentrated magnetic material are discussed.     

The spin structure of the effective quark Hamiltonian and the hyperfine splittings of charmonium

We provide a simple classical derivation on the spin dependent part of the effective quark Hamiltonian. We suggest that the large S-state hyperfine splitting can be resolved by interpreting that the quark confinement potential is mainly due to an effective scalar exchange.     

Magnetic moments and electronic structure of Co-base metallic glasses

Magnetization of Co_80-xT_xB₂₀ glasses (0 ≤ × ≤ 12 at%, T = Fe, Mn, Cr, V) has been measured from 4.2 K to approximately 700 K. The data are well described in terms of the virtual bound states introduced above the center of the d band of the matrix by the light T solutes. Details of the electronic structure, some aspects of which would not be revealed by photoemission, are thereby inferred.     

Permanent dipole moments and multi-photon resonances

The effects of non-zero diagonal dipole matrix elements on multi-photon resonance profiles, for the interaction of molecules with a sinusoidal field, are discussed by using an expression for the profiles derived in the rotating wave approximation. The validity of this result is discussed with reference to exact two-level model calculations.     

Magnetic moments,E3 transitions and the structure of high-spin core excited states in 211Rn

The results of g-factor measurements of high-spin states in ²¹¹Rn are: $\text{E}{}_{\mathrm{<mtext>x</mtext>}}\text{= 8856 + Δ′}\text{keV}\text{(J}{}^{\mathrm{\pi }}\text{=}\text{63}\text{2}{}^{\mathrm{?}}\text{)}$, g = 0.626(7); $\text{6101 + Δ′}\text{KeV}\text{(}\text{49}\text{2}{}^{\mathrm{+}}\text{), 0.766(8)}$; $\text{5347 + Δ′}\text{KeV}\text{(}\text{43}\text{2}{}^{\mathrm{?}}\text{), 0.74(2)}$; $\text{3927 + Δ}\text{KeV}\text{(}\text{35}\text{2}{}^{\mathrm{+}}\text{), 1.017(12)}$; $\text{1578 + Δ}\text{KeV}\text{(}\text{17}\text{2}{}^{\mathrm{?}}\text{), 0.912(9)}$. These results together with measured E3 transition strengths and shell model calculations are used to assign configurations to the core excited states in ²¹¹Rn. Mixed configurations are required to explain the g-factors and enhanced E3 strengths simultaneously.