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Tel Aviv University, Diss., 2005; 78 pp., (2005). doi:10.3204/DESY-THESIS-2005-018, Published by Deutsches Elektronen-Synchrotron, DESY, Hamburg

Double-spin asymmetries of semi-inclusive cross sections for the production of identified pions and kaons have been measured in deep-inelastic scattering of polarized positrons on a polarized deuterium target. Five helicity distributions including those for three sea quark flavors were extracted from these data together with re-analyzed previous data for identified pions from a hydrogen target. These distributions are consistent with zero for all three sea flavors. A recently predicted flavor asymmetry in the polarization of the light quark sea appears to be disfavored by the data.

Simon Fraser University, Diss., 2003; 219 pp., (2003). doi:10.3204/DESY-THESIS-2003-032, Published by Deutsches Elektronen-Synchrotron, DESY, Hamburg

The NuTeV experiment has measured sin^2Theta_W = 0.2277 +/- 0.0013(stat) +/- 0.0009(syst), approximately 3 standard deviations above the standard model prediction. This discrepancy has motivated speculation that the NuTeV result may be affected significantly by neglected experimental or theoretical effects. We examine the case for a number of proposed explanations.

97 pp. (2003)., This document outlines the case for a programme of electron-deuteron scattering mea- surements at HERA using the H1 detector. The goals of the $e^\pm D$ programme are to map the partonic structure of the nucleon at large $Q^2$ and low $x$, to explore the valence quark distributions at the highest $x$ values, to provide a precise measurement of the strong coupling constant and to investigate the parton recombination phenomena revealed in shadowing and their relationship to diffraction. The importance of these measurements for the under- standing of the perturbative and non-perturbative aspects of QCD thought to be responsible for nucleon structure is discussed, as is the significance of the measurements for future experimental programmes. Some modifications to both the H1 apparatus and the HERA accelerator are necessary to realise this programme; these are presented in the document. Mention is also made of questions that will remain unanswered following the completion of the above programme and the potential role of HERA and of H1 in investigating these questions is outlined.Physicists and Institutes interested in supporting this project are asked to inform Max Klein (klein@ifh.de) and Tim Greenshaw (green@hep.ph.liv.ac.uk) that they would like to have their names on the Letter of Intent by Wednesday 30th April 2003.

Universität Freiburg, Diss., 2001; 122 pp. (2001). = Universität Freiburg, Diss., 2001

Humboldt Universität zu Berlin, Diss., 2001; 205 pp. (2001). = Humboldt Universität zu Berlin, Diss., 2001

Universität Freiburg, Diss., 2001; 124 pp. (2001). = Universität Freiburg, Diss., 2001

Universität Hamburg, Diss., 2001; 211 pp. (2001). = Universität Hamburg, Diss., 2001

Physical review letters 87(14), 142302 (2001). doi:10.1103/PhysRevLett.87.142302, We introduce generalized quark and gluon distributions in the deuteron, which can be measured in exclusive processes like deeply virtual Compton scattering and meson electroproduction. We discuss the basic properties of these distributions, and point out how they probe the interplay of nucleon and parton degrees of freedom in the deuteron wave function., Published by APS, College Park, Md.

We show that in hard exclusive electroproduction, ep-->eVp, the leading-twist hard-scattering coefficient for the production of a transversely polarized vector meson V vanishes to all orders of perturbation theory. This implies that this process cannot be used to measure the skewed transversity distribution of quarks in a hadron. In contrast, a recent calculation obtained a non-zero value at NLO. We show that this calculation is incorrect because it failed to include the necessary collinear subtractions. Our method of proof also applies to other processes whose hard-scattering coefficients are constrained by chirality and helicity conservation, and thus validates helicity selection rules based on these symmetries., 5 pages, 3 figures, ReVTeX

137 pp. (1999)., The outline of this work is as follows. Chapter 2 gives an introduction to polarised deep inelastic scattering and provides the formalism used to extract the quark spin distributions from inclusive and semi-inclusive spin-dependcnt cross section asymmetries. In chapter 3 the HERMES experimental apparatus is introduced. The analysis of inclusive and semi-inclusive charged hadron asymmetries is presented in chapter 4 and the extraction of the polarised quark distributions from the measured cross section asymmetries is described in chapter 5. The HERMES results on the polarised quark distributions are discussed and compared to existing experimental results and to predictions from quark models and lattice QCD.

Zeitschrift für Physik / C 70, 273-280 (1996). doi:10.48550/arXiv.hep-ph/9507271, Nonsinglet contributions to the $g_1(x,Q^2)$ structure function are calculated in the double-logarithmic approximation of perturbative QCD in the region $x \ll 1$. Double logarithmic contributions of the type $(\alpha_s \ln ^2 (1/x))^k$ which are not included in the GLAP evolution equations are shown to give a stronger rise at small-x than the extrapolation of the GLAP expressions. Further enhancement in the small-x region is due to non-ladder Feynman graphs which in the DLA of the unpolarized structure functions do not contribute. Compared to the conventional GLAP method (where neither the whole kinematical region which gives the double logs nor the non-ladder graphs are taken into account) our results lead to a growth at small-x which, for HERA parameters, can be larger by up to factor of 10 or more., Published by Springer, Heidelberg

6 pp. (1995)., Precise determinations of the strong coupling constant in hadronic collisions demand sets of parton densities spanning a sufficiently wide range of values for the QCD scale parameter Λ. For such applications, we supplement the recent GRV parametrization by five sets of dynamically generated parton distributions for Λ-values corresponding to αS(MZ2) between 0.104 and 0.122. Present DIS data, including recent small-x HERA results, do not appreciably discriminate between these sets.

15 pp. (1994)., A next--to--leading order QCD analysis of deep inelastic scattering data is performed allowing for contributions due to a light gluino. We obtain the values of $\alpha_s(M_Z^2) \pm \delta \alpha_s^{stat} = 0.108 \pm 0.002, 0.124 \pm 0.001, 0.145 \pm 0.009$ for QCD, SUSY QCD with a Majorana gluino and a Dirac gluino respectively. The value of $\alpha_s(M_Z^2)$ obtained in SUSY QCD with a Majorana gluino best agrees with the direct measurements of $\alpha_s(M_Z^2)$ at LEP.

8 pp. (1993)., High-$p⊥$ jets in diffractive pp events have revealed a parton structure in the exchanged pomeron. Based on a model using a pomeron structure function dominated by either quarks or gluons we calculate diffractive W/Z production and find observably large cross-sections at the Tevatron energy. The relative quark and gluon content may here be experimentally investigated and the x-shape of their density functions obtained to give new insights on the nature of the pomeron