Phenomenological determination of polarized quark distributions in the nucleon

We present a fit to spin asymmetries which gives polarized quark distributions. These functions are closely related to the ones given by the Martin, Roberts and Stirling fit for unpolarized structure functions. The integrals of polarized distributions are discussed and compared with the corresponding quantities obtained from neutron and hyperon??-decay data. We use the combination of proton, neutron and deuteron spin asymmetries in order to determine the coefficients of our polarized quark distributions. Our fit shows that phenomenologically there is no need for taking polarized gluons into account.     

Phenomenological determination of polarized quark distributions in the nucleon

We present a fit to spin asymmetries which gives polarized quark distributions. These functions are closely related to the ones given by the Martin, Roberts and Stirling fit for unpolarized structure functions. The integrals of polarized distributions are discussed and compared with the corresponding quantities obtained from neutron and hyperonβ-decay data. We use the combination of proton, neutron and deuteron spin asymmetries in order to determine the coefficients of our polarized quark distributions. Our fit shows that phenomenologically there is no need for taking polarized gluons into account.     

A measurement of the proton structure functions from neutrino-hydrogen and antineutrino-hydrogen charged-current interactions

Within the framework of the quark-parton model, the quark and anti-quark structure functions of the proton have been measured by fitting them to the distributions of the events in the Bjorkeny variable. The data used form the largest sample of neutrino and antineutrino interactions on a pure hydrogen target available, and come from exposures of BEBC to the CERN wide band neutrino and antineutrino beams. It is found that the ratiod _v /u _v of valence quark distributions falls with increasing Bjorkenx. In the context of the quark-parton model the results constrain the isospin composition of the accompanying diquark system. Models involving scattering from diquarks are in disagreement with the data.     

Spin physics in the high energy hadron productions. A systematic study of the spin asymmetries induced by <Emphasis Type="Italic">pp, γp,ep</Emphasis> and λ<Emphasis Type="Italic">p</Emphasis> collisions

The spin polarizations of hadrons inclusively produced by pp, γp and λp collisions are studied by the quark rearrangement model. The present model is a phenomenological one based on the relativistic spin equations of motion and using the quark distribution functions in hadrons and photon. A general success of the model is demonstrated. We find usefulness of the present formulation for studying the dynamics producing spin asymmetry distributions and the statics determining signs and magnitudes of the spin polarization by reflecting the characteristic quark structure in hadrons.     

The Ochs-Stodolsky jet profile in iterative quark cascade models and low p⊥ meson fragmentation

We show that the Ochs-Stodolsky jet profile distributions [1,2] have a simple and natural interpretation in a general class of iterative quark cascade models. From a model of the relationship between the meson distributions in mesonic low p_⊥-fragmentation regions and the quark fragmentation functions [6] we obtain predictions between jet-profile distributions in inelastic non-diffractive meson reactions.     

Imaging the Transverse (Spin) Structure of Hadrons

Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when the target and/or quark are transversely polarized. Connections between this deformation and transverse single-spin asymmetries as well as with quark–gluon correlations are discussed. The sign of transverse deformation of impact parameter dependent parton distributions in a transversely polarized target can be related to the sign of the contribution from that quark flavor to the nucleon anomalous magnetic moment. Therefore, the signs of the Sivers function for u and d quarks, as well as the signs of quark–gluon correlations embodied in the polarized structure function g ₂ can be understood in terms of the proton and neutron anomalous magnetic moments.     

xF 3 structure function based on the associated Jacobi polynomials

We present the results of the Next-to-leading order (NLO) non-singlet QCD analysis of the experimental data of the CCFR collaboration for the xF ₃ structure function of the deep-inelastic scattering of neutrinos on the nucleon in based on the associated Jacobi polynomials expansion of the structure functions. The structure function is reconstructed from its moments by using the expansion in terms of orthogonal associated Jacobi polynomials. Our results of valence quark distributions are in good agreement with the available theoretical models.     

Inclusive interactions of high-energy neutrinos and antineutrinos in iron

We present results on charged current inclusive neutrino and antineutrino scattering in the neutrino energy range 30–200 GeV. The results include a) total cross-sections; b)y distributions; c) structure functions; and d) scaling violations observed in the structure functions. The results, as well as their comparison with the results of electron and muon inclusive scattering, are in agreement with the expectations of the quark parton model and QCD.     

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.     

Gottfried sum rule and the shape ofF 2 ⌍ -F 2 ⌍

The recent experimental determination of the Gottfried sum rule of deep inelastic scattering provides strong evidence that SU(2) flavor symmetry is broken by the sea quark distributions of the nucleon. Two mechanisms have been suggested to explain the data: Pauli blocking and non-perturbative contributions to the sea arising from the pion cloud surrounding the nucleon. We investigate the effects of these two mechanisms on several standard parametrizations of the quark distribution functions and find that each mechanism has different effects on the shapes of these distribution functions. The best agreement between the experimental data and the modified quark distributions occurs when both mechanisms are taken into account using a softπNN form factor and a small Pauli correction.     

Covariant trace formalism for heavy mesons-wave top-wave transitions

Heavy meson,s- top-wave, weakb→c transitions are studied in the context of the heavy quark effective theory using covariant meson wave functions. We use the trace formalism to evaluate the weak transitions. As expected from heavy quark symmetry, the eight transitions betweens- andp-wave states are described in terms of only two universal form factors which are given in terms of explicit wave function overlap integrals. We present our results in terms of both invariant and helicity amplitudes. Using our helicity amplitude expressions we discuss rate formulae, helicity structure functions and joint angular decay distributions in the decays \(\bar B \to D^{**} ( \to (D,D^* ) + \pi ) + W^ - ( \to l^ - \bar v_l )\) . The heavy quark symmetry predictions for the one pion transitionsD ^**→(D,D ^*)+π are similarly worked out by using trace techniques.     

Studies of the EMC effect in the QCD framework with the EMC iron and hydrogen structure functions

The QCD evolution of the measured structure functions F₂ in iron and hydrogen have been analysed to show that the momentum distribution of the valence quarks is lower in iron than in hydrogen and that the opposite is true for the gluon and sea quark distributions in the region of 0.1<x<0.65.     

Electroweak radiative corrections and quark mass singularities

A consistent method to remove quark mass singularities from physical cross sections is demonstrated. They are factorised into quark and gluon distribution functions. This implies electromagnetic correction terms to theQ ² dependent structure functions. They are calculated in leading order in the fine structure constant α and found to be flat and small overx.     

Phenomenological determination of polarized quark distributions in the nucleon

We present a fit to spin asymmetries which gives polarized quark distributions. These functions are closely related to the ones given by the Martin, Roberts and Stirling fit for unpolarized structure functions. The integrals of polarized distributions are discussed and compared with the corresponding quantities obtained from neutron and hyperonβ-decay data. We use the combination of proton, neutron and deuteron spin asymmetries in order to determine the coefficients of our polarized quark distributions. Our fit shows that phenomenologically there is no need for taking polarized gluons into account. Work supported in part by the KBN-Grant 2-P302-143-06     

Observation of scaling deviations in the energy distribution of secondary hadrons in inelastic neutrino-proton interactions

An analysis is presented of the z distributions of secondary hadrons produced in 5600 charged current events from a BEBC neutrino-hydrogen experiment. Evidence is presented for scaling deviations in the z distributions and a breakdown of factorization in the single particle inclusive cross sections. The results are consistent with the leading order QCD predictions on the q² dependence of nonsinglet moments of quark fragmentation functions, yielding a value of Λ ≈ 0.6 GeV.     

QCD three-jet production in large-p⊥ processes

The contribution of the hard scattering subprocess quark + quark → quark + quark + gluon to two-particle inclusive distributions at large p_⊥ is studied. It is shown to be accessible experimentally, and agrees with recent data on azimuthal distributions in the adequate kinematical region.     

Anomalous cross section for photon-photon scattering in gauge theories

We consider the deep inelastic structure functions of the photon in an asymptotically free gauge theory. In contrast to the case of a hadronic target, we find that the shortdistance analysis determines the shape and magnitude and not merely the Q² dependence of the structure functions. The structure functions of the free quark theory are renormalized by finite, calculable factors. For example, at x = 0.1, we find that F₂ will, at large Q², exceed the free quark result by a factor 1.751, while for x = 0.5, F₂ is suppressed asymptotically, relative to the free quark theory, by a factor 0.964, and at x = 0.8, by a factor 0.611.     

QCD Evolution of Nuclear Structure Functions at Large X: EMC Effect and Cumulative Processes

QCD evolution of nuclear structure functions at large x is reviewed within the an approach based on QCD factorization for hard processes and multiquark flucton model. In this approach, x > 1 region of the nuclear structure functions is intimately related with x < 1 region due to manifestation of quark and gluon degrees of freedom in nuclei. Properties of QCD evolution and observed EMC-ratio for nuclear structure functions at x < 1 result in an admixture of hard extra sea quark distribution. This extra nuclear quark sea provides a bump above unity for EMC-ratio at small x and becomes dominant in the nuclear quark sea for cumulative region x > 1. It leads to a striking prediction, confirmed by data, for the same spectrum slopes of all cumulative hadrons in nuclear fragmentation region.