Gluon polarization in the proton

We combine heavy-quark renormalization group arguments with our understanding of the nucleon's wavefunction to deduce a bound on the gluon polarization Delta g in the proton. The bound is consistent with the values extracted from spin experiments at COMPASS and RHIC.Comment: 4 page

Promising Practice: Book Studies as Professional Development for Rural Teachers

This promising practice article describes conducting book studies as professional development in rural communities. In this article, we share our understanding of the importance of this type of professional development in rural schools, as well as considerations for those who wish to start something similar in their districts

Dynamics of the Landau-Pomeranchuk-Migdal Effect in Au+Au Collisions at 200 AGeV

We study the role played by the Landau-Pomeranchuk-Midgal (LPM) effect in relativistic collisions of hadrons and heavy nuclei, within a parton cascade model. We find that the LPM effect strongly affects the gluon multiplication due to radiation and considerably alters the space-time evolution of the dynamics of the collision. It ensures a multiplicity distribution of hadrons in aggreement with the experimental proton-proton data. We study the production of single photons in relativistic heavy ion collisions and find that the inclusion of LPM suppression leads to a reduction in the single photon yield at small and intermediate transverse momenta. The parton cascade calculation of the single photon yield including the LPM effect is shown to be in good agreement with the recent PHENIX data taken at the Relativistic Heavy-Ion Collider.Comment: 12 pages, 4 figure

The nucleon's octet axial-charge g_A^8 with chiral corrections

The value of the nucleon's flavour-singlet axial-charge extracted from polarised deep inelastic scattering is sensitive to the value of the octet axial-charge g_A^8 which is usually taken from an analysis of hyperon beta-decays within the framework of SU(3) symmetry, namely 0.58 \pm 0.03. Using the Cloudy Bag model we find that the value of g_A^8 is reduced by as much as 20% below the usual phenomenological value. This increases the value of the flavour singlet axial charge (g_A^0|_inv) derived from deep inelastic data and significantly reduces the difference between it and g_A^8.Comment: 12 page

Spin and orbital angular momentum of the proton

Since the announcement of the proton spin crisis by the European Muon Collaboration there has been considerable progress in unravelling the distribution of spin and orbital angular momentum within the proton. We review the current status of the problem, showing that not only have strong upper limits have been placed on the amount of polarized glue in the proton but that the experimental determination of the spin content has become much more precise. It is now clear that the origin of the discrepancy between experiment and the naive expectation of the fraction of spin carried by the quarks and anti-quarks in the proton lies in the non-perturbative structure of the proton. We explain how the features expected in a modern, relativistic and chirally symmetric description of nucleon structure naturally explain the current data. The consequences of this explanation for the presence of orbital angular momentum on quarks and gluons is reviewed and comparison made with recent results from lattice QCD and experimental data.Comment: Lectures at Aligarh University (4th DAE-BRNS Workshop on Hadron Physics, Feb 18-21, 200

The Spin Structure of the Proton and Polarized Collider Physics

We summarise the present status of the proton spin problem and the physics possibilities for future polarized ep and pp colliders. This summary is based on the presentations and discussion sessions at the workshop ``The Spin Structure of the Proton and Polarized Collider Physics'' (Trento, July 23-28, 2001).Comment: 27 pages, 22 figure

Eta bound states in nuclei: a probe of flavour-singlet dynamics

We argue that eta bound states in nuclei are sensitive to the singlet component in the eta. The bigger the singlet component, the more attraction and the greater the binding. Thus, measurements of eta bound states will yield new information about axial U(1) dynamics and glue in mesons. Eta - etaprime mixing plays an important role in understanding the value of the eta-nucleon scattering length.Comment: 8 pages, version to appear in PL

Interplay of Spin and Orbital Angular Momentum in the Proton

We derive the consequences of the Myhrer-Thomas explanation of the proton spin problem for the distribution of orbital angular momentum on the valence and sea quarks. After QCD evolution these results are found to be in very good agreement with both recent lattice QCD calculations and the experimental constraints from Hermes and JLab