Spin-dependent parton distributions in polarized deep inelastic lepton nucleon scattering

We analyze the recently measured first moment Г ^p (Q ²) of the structure functiong ₁ ^p (x,Q ²) obtained in deep inelastic scattering of polarized electrons from polarized protons. It is shown that the recent experimental result Г ^p (〈Q ²〉?10 GeV²)? 0.113 implies a polarized strange quark sea whose total polarization Δs(μ²)??0.22 is comparable to Δμ(μ²)?0.74 and Δd(μ²)??0.50 already at a typically hadronic scale μ=0(1 GeV). Most remarkably, the total polarization due to quark distributions Δμ(μ²)+Δd(μ²)+Δs(μ²) practically vanishes which implies that the spin of the proton is carried by the gluons, ΔG(μ²), and/or the angular momentum of the partons. This surprising conjecture can be experimentally tested with heavy quark production in longitudinally polarized lepton-nucleon scattering. In particular the (real) photon-gluon fusion process γg→Q \(\bar Q\) provides a rather unique measure of ΔG(x,Q ²).     

Determination of the gluon distribution in the nucleon from deep inelastic neutrino scattering

The observed scaling violations of the nucleon structure functionF ₂ and \(\bar q\) have been analysed in the framework of perturbative QCD to determine the shape and magnitude of the gluon distribution. The data are in good agreement with leading order QCD, and the simultaneous use ofF ₂ and \(\bar q\) structure functions permits, for the first time, a reliable determination of the gluon structure function.     

Probing nucleon strange asymmetry from charm production in neutrino deep inelastic scattering

We propose a means to detect the nucleon strange quark-antiquark asymmetry, which is predicted as a non-perturbative effect, but still unchecked directly by available experiments. The difference for the and meson production cross sections in neutrino and antineutrino induced charged current deep inelastic scattering is illustrated to be sensitive to the nucleon strange asymmetry. A prospect is given and the effect due to the light quark fragmentation is also discussed for the extraction of the strange asymmetry in future experiments.Received: 23 April 2005, Published online: 27 July 2005PACS: 14.60.Pq, 12.15.Ff     

Multiplicity distributions from quarks and diquarks in deep inelastic lepton-nucleon scattering

We present an analytic prediction for the full hadronic multiplicity distribution in deep-inelastic lepton-nucleon scattering. We obtain a distinctive relationship between the average multiplicity at any W and that in e⁺e^? annihilation.     

Implications of new deep inelastic scattering data for parton distributions

We perform a next-to-leading order structure function analysis of μN and νN deep inelastic data in an attempt to resolve the disagreement between recent EMC and BCDMS measurements of F₂ for μp scattering. Equally acceptable QCD fits are obtained including either set of μN data, but a comparison with Drell-Yan data appears to favour the parton distributions derived from the BCDMS data.     

Parton distributions from a global QCD analysis of deep inelastic scattering and lepton-pair production

Parton distribution functions consistent with neutrino and muon deep inelastic scattering as well as Drell-Yan pair production results have been extracted. This analysis incorporates experimental systematic errors which are the dominant errors in recent deep inelastic scattering experiments. The dependence of the results on factors such as kinematic cuts in the data, heavy target corrections, and choice of initial functional form are also explored. The form adopted is motivated by perturbative QCD and particularly useful in exploring the small-x extrapolation of the distributions. This is crucial for studying the range of predictions for Collider, HERA, and SSC/LHC cross sections. Representative distribution function sets are presented in a very compact parametrized form both in the DIS and MS-bar renormalization schemes.This work is partially supported by the National Science Foundation under Grant No. PHY89-05161. This work was also supported by Argonne National Laboratory during the 1988–89 academic year when the author was on Sabbatical leave at the Laboratory from IIT     

Width-fluctuation effects in angular correlation in inelastic nucleon scattering

The effects of level-width fluctuations on the nucleon-gamma angular correlations and double-differential cross sections have been studied on the basis of Moldauer's formulation. Computational procedures for pursuing the width-fluctuation studies on a routine basis for reactions following the compound nucleus mechanism have been developed. The width-fluctuation effects in (n, n'γ) reactions with ²⁴Mg and ⁵⁶Fe have been calculated. These calculations indicate that the inclusion of width-fluctuation considerations significantly reduces the double differential cross sections compared to those made on the basis of Hauser-Feshbach theory. However, as expected, the shape of the angular correlation function is not siginificantly altered by the width-fluctuation corrections.     

Isobaric distributions in deep inelastic reactions

Stimulated by at first sight mutually contradicting experimental results, the present paper investigates the origin of fluctuations in the charge equilibration of deep inelastic collisions. Two extreme models, the one stressing the collective aspect, the other the independent particle picture, are discussed. Both models indicate the usefulness of a simple formula which connects the standard deviation with the nuclear temperature. There is no need to introduce quantum fluctuations in order to explain the current experimental data.     

Diquark contributions to the nucleon deep inelastic structure functions

The contributions of diquarks to the nucleon structure functions are discussed in the framework of the parton model and in the most general case of both vector and scalar diquarks inside unpolarized and polarized nucleons. The vector diquark anomalous magnetic moment and the scalar-vector and vector-scalar diquark transitions are also taken into account. The properties of the diquarks and of their form factors, required in order for the resulting scaling violations to be compatible with the observed ones, are discussed.     

Calculation of nuclide distributions in deep inelastic scattering and the production of neutron rich nuclei

Nuclide distributions for deep inelastic fragments are calculated considering the diffusion of the intermediate dinuclear system in a two-dimensional liquid drop potential energy surface. Particle decay from the fragments is taken into account by statistical model calculations. The concept of charge equilibration is investigated. Calculations are compared to previously measured nuclide distributions. Predictions are made for the production cross sections of neutron-rich nuclei in deep inelastic reactions.     

Shadowing in deep inelastic muon scattering from nuclear targets

Results are presented on the ratio of the inelastic muon-nucleus cross section per nucleon for carbon and calcium relative to that for deuterium. The measurements were made in the kinematic range of low x (0.003–0.1) and low Q² (0.3–3.2 GeV²) at an incident muon energy of 280 GeV. The calcium to deuterium ratio shows a significant x dependence which is interpreted as a shadowing effect. No strong Q² dependence is observed. This suggests that the effect is due at least partially to parton interactions within the nucleus.     

Pion fluctuation in deep inelastic scattering

The forward neutron production in the ep collisions at 300GeV measured by H1 and ZEUS Collaborations at DESY has been used to estimate the total probability for proton fluctuation into nπ⁺ and pπ⁰. The probability found is on the order of 30%. This number is compared with the numbers obtained for the probability of quark fluctuation into π⁺ from several alternative DIS processes (Gottfried sum rule, polarized structure function) and the axial-vector coupling constant, where the pion fluctuation is believed to play an important role.