Spin-dependent Structure Function Research Articles

A model of deep inelastic polarized electroproduction

A realistic phenomenological model combining parton/QCD ideas with lower energy SU(6) constraints is proposed for the shape and evolution of the leading spin-dependent structure function G ep( x, Q 2) in polarized electroproduction. Close's broken-SU(6) ansatz is used to relate appropriately defined polarized quark-parton distribution densities to unpolarized ones at the matching momentum scale Q 2 = Q 0 2. The differences between spin and helicity distribution densities as well as the complications due to perturbative QCD and parton k T (with related target-mass) effects are taken into account. Evolution to higher (>10 GeV 2) values of Q 2 (where target-mass effects can be neglected) yields experimentally testable numerical predictions that are presented through various plots. The value of Q 0 is self-consistently determined to be about 0.5 GeV.

Quantum chromodynamics corrections to polarised deep-inelastic electron-nucleon scattering

Quantum chromodynamics corrections to orderα s (the running coupling constant), using the quark-parton approach are calculated for the spin-dependent structure functions in deep-inelastic polarised electron-nucleon scattering. Consequences of these corrections for the Bjorken sum rule and the asymmetry in the case of longitudinally polarised (with respect to the beam) nucleons is discussed which could provide possible tests of quantum chromodynamics. Comparison of our results with the moments of the flavour non-singlet contribution to the structure functions obtained using operator product expansion is also given.

GROUND STATE FLUCTUATIONS IN POLARIZED3He

The ariational approach is adopted to describe mass- and spin-density fluctuations in po- Y larized 1 iquid He. The ground state is approximated by a suitable Jastrow-Slater wave function which incorporates the effects of spatial correlations. The newly developed Fermi-hypernetted chain theory is employed to analyse the associated theoretical particle - and spin-dependent structure functions, spin-fl ip functions, momentum distribution and one-body density matrix. Numerical results on these quantities are presented for liquid 3~e in the unpolarized and completely polarized state, The effect of polarization on the structure- and radial distribution function is studied in detail, A preli'mf- nary numerical estimate is presented for the magnetic equatl'on of state,

Spin-dependent photon structure functions

The spin-dependent structure functions of the photon are calculated using the operator product expansion renormalisation group equation approach. The possibilities of measuring the photon structure function in photon-induced Drell-Yan and in two-photon processes in e+e- reactions are discussed.

Comment on theG2structure function in the MIT bag model

The corrected expression for the deep-inelastic spin-dependent structure function G/sub 2/, calculated in the cavity approximation to the MIT bag model, is presented. Although we get new additional terms in this expression, the previously calculated sum rule for this function is not affected.

Scaling violations for the spin-dependent structure function G1

With the formalism of Altarelli and Parisi, we study scaling violations for the spin dependent structure function G 1. We find that the variation of G 1 with Q 2 is essentially determined by that of the valence quarks helicity distributions, the antiquark densities contributing negligibly.

Spin distributions in the quark parton model

Spin-dependent parton distributions are described in a broken SU(6) quark parton model. The model predicts definite forms for the spin-dependent structure functions in deep inelastic lepton-nucleon scattering and leads to several relations between Regge intercepts and couplings. Resonance electroproduction at large momentum transfer is explored via Bloom-Gilman duality.

Chiral Substructure of the Nucleon

The representation mixing induced by the spontaneous breaking of chiral symmetry is a spatially varying phenomenon. A model for this effect predicts the form of the spin-dependent structure functions of deep inelastic lepton scattering and leads to the relation 1-..cap alpha../sub A/1(0) =2(1-..cap alpha../sub rho/(0)).

A simple derivation of schwinger’s sum rule for spin-dependent structure functions

Schwinger’s new sum rule for the spin-dependent structure functions is derived from the superconvergence principle. The Regge behaviour of the virtual photon-nucleon scattering amplitude is deduced from the Van Hove model from which a superconvergence relation is shown to follow leading to the sum rule. The saturation of the sum rule is discussed.

Spin-dependent deep inelastic electron scattering in an asymptotically free gauge theory

We compute the logarithmic deviations from Bjorken scaling for the spin dependent structure functions of deep inelastic electron scattering in an asymptotically free gauge theory. Continuations to the elastic limit and to the Regge region are also considered.

SU 6 Quark model, nucleon resonance electroproduction and spin-dependent electroproduction structure functions

The electromagnetic resonance excitation form factors for proton and neutron initial states are calculated in the nonrelativistic symmetric quark model for resonances in the 56 (L = 0), 70 (L = 1) and 56 (L = 2). Initially the radial wave function for each supermultiplet is assumed arbitrary and the results are used to calculate the resonance part of both spin independent and dependent electroproduction structure functions. Following Close, Gilman and Karliner the scaling behaviour of the structure functions is then discussed and relations with the naive quark-parton model made. Further a common radial wave function for all of the supermultiplets is assumed so there is then just a single undetermined form factor. Sum rules such as the Cabibbo-Radicati are considered and by demanding their saturation by the 56 and 70 additional dynamical constraints are derived. The observed helicity structure for excitation of theD13 andF15 is shown to arise naturally and change less dramatically withq2 than for a harmonicoscillator model.

Spin-dependent deep inelastic electron-proton scattering

The two spin-dependent structure functions in electroproduction cross sections are investigated asymptotically. It is suggested that the amplitude for spin-dependent virtual Compton scattering at large space-like photon masses is controlled by the dominant J-plane singularities and the constitution of the electric current. Experimental and theoretical implications of this conjecture are discussed.