Exploring the Spin Structure of the Proton with Two-Body Partonic Scattering at RHIC

The STAR collaboration at the Relativistic Heavy Ion Collider is using polarized proton beams at sqrt{s} = 200 GeV to study the spin structure of the proton. The first results for the double spin helicity dependence of inclusive jet production are presented along with projections for additional data taken in 2005 and 2006. When fully analyzed these data sets should place strong constraints on the possible contribution of gluonic spin to the proton spin as expressed by Delta G. Future studies using 2-jet or photon-jet coincidences to map out the gluon spin distribution vs. the gluon's momentum fraction of the proton are discussed.Comment: 4 pages, 2 figures, presented at the 18th Int. IUPAP Conf. on Few-Body Problems in Physics, Santos, Sao Paulo, Brazil, August 21-26,200

Generalized transparency in semi-inclusive processes

It is argued that the transparency of a medium for passage of a nucleon, knocked-out in a semi-inclusive $(e,e'p)$ reaction and subsequently scattered elastically, is not the same as the one measured in purely elastic scattering. Expressions are given for the properly generalized transparency and those are compared with recently proposed, alternative suggestions. Numerical results are presented for selected nuclear targets and kinematic conditions, applying to the Garino et al and the SLAC NE18 experiment.Comment: 24p.; added topdraw file for figures; WIS-93/48/Jun-P

Transverse Momentum in Semi-Inclusive Polarized Deep Inelastic Scattering and the Spin-Flavor Structure of the Proton

The non-valence spin-flavor structure of the nucleon extracted from semi-inclusive measurements of polarized deep inelastic scattering depends strongly on the transverse momentum of the detected hadrons which are used to determine the individual polarized sea distributions. This physics may explain the recent HERMES observation of a positively polarized strange sea through semi-inclusive scattering, in contrast to the negative strange sea polarization deduced from inclusive polarized deep inelastic scattering.Comment: 4 pages, revtex style, 2 figure

Theoretical aspects of the CEBAF 89-009 experiment on inclusive scattering of 4.05 GeV electrons from nuclei

We compare recent CEBAF data on inclusive electron scattering on nuclei with predictions, based on a relation between structure functions (SF) of a nucleus, a nucleon and a nucleus of point-nucleons. The latter contains nuclear dynamics, e.g. binary collision contributions in addition to the asymptotic limit. The agreement with the data is good, except in low-intensity regions. Computed ternary collsion contributions appear too small for an explanation. We perform scaling analyses in Gurvitz's scaling variable and found that for $y_G\gtrless 0$, ratios of scaling functions for pairs of nuclei differ by less than 15-20% from 1. Scaling functions for $0$ are, for increasing $Q^2$, shown to approach a plateau from above. We observe only weak $Q^2$-dependence in FSI, which in the relevant kinematic region is ascribed to the diffractive nature of the NN amplitudes appearing in FSI. This renders it difficult to separate asymptotic from FSI parts and seriously hampers the extraction of $n(p)$ from scaling analyses in a model-independnent fashion.Comment: 11 p. Latex file, 2 ps fig

Unraveling hadron structure with generalized parton distributions

The generalized parton distributions, introduced nearly a decade ago, have emerged as a universal tool to describe hadrons in terms of quark and gluonic degrees of freedom. They combine the features of form factors, parton densities and distribution amplitudes--the functions used for a long time in studies of hadronic structure. Generalized parton distributions are analogous to the phase-space Wigner quasi-probability function of non-relativistic quantum mechanics which encodes full information on a quantum-mechanical system. We give an extensive review of main achievements in the development of this formalism. We discuss physical interpretation and basic properties of generalized parton distributions, their modeling and QCD evolution in the leading and next-to-leading orders. We describe how these functions enter a wide class of exclusive reactions, such as electro- and photo-production of photons, lepton pairs, or mesons. The theory of these processes requires and implies full control over diverse corrections and thus we outline the progress in handling higher-order and higher-twist effects. We catalogue corresponding results and present diverse techniques for their derivations. Subsequently, we address observables that are sensitive to different characteristics of the nucleon structure in terms of generalized parton distributions. The ultimate goal of the GPD approach is to provide a three-dimensional spatial picture of the nucleon, direct measurement of the quark orbital angular momentum, and various inter- and multi-parton correlations.Comment: 370 pages, 62 figures; Dedicated to Anatoly V. Efremov on occasion of his 70th anniversar

Structure and metamorphism at the western margin of the Omineca belt near Boss mountain, east central British Columbia

Rocks of the Hadrynian and Early Paleozoic (?) Snowshoe Group comprise the core of the Boss Mountain area at the western margin of the Omineca Belt near Crooked Lake. Structurally overlying these are rocks of the Intermontane Belt: the Permian Slide Mountain Group (Antler Formation), Triassic fine grained sediments (unnamed), and Jurassic volcanic rocks (Takla Group). In the Snowshoe Group, a large, lensoid intrusion of coarse grained granitic rock (Boss Mountain gneiss) was emplaced during the mid-Paleozoic, and later deformed and metamorphosed with the enclosing metasediments. The rocks of the Snowshoe Group act as basement to the overlying Late Paleozoic/Early Mesozoic cover rocks. Within the basement, four phases of regionally significant deformation have been recognized, and are manifest as fold generations designated Fl through F4. Earliest structures, Fl, in the Snowshoe Group are isoclinal folds, accompanied by a transposed foliation of regional extent, which are overprinted by penetrative deformation related to easterly verging F2 nappe structures. The F3 folds are upright or inclined to the northeast, and give a consistent southwesterly sense of vergence. These folds are responsible for the regional map pattern, and have folded both the basement and cover into an antiformal culmination in the Boss Mountain area. Fourth phase structures refold the other features, but do not appreciably affect the F3 geometry. In the cover sequences, the first phase of deformation is equivalent to the second phase within the basement During the Phase 2 deformational episode the cover rocks were emplaced over rocks of the Snowshoe Group. West-dipping imbricate faults characterize the western margin of the area, where basement rocks contain fault-bounded slivers of the cover, and the tectonic contact between basement and cover rocks is marked by a zone of mylonitization. Similarly, the F2 and F3 folding phases in the cover are equivalent to the F3 and F4 structures in the basement, respectively, but are only weakly developed in the cover. An early, enigmatic metamorphic event accompanied Phase 1 deformation in rocks of the Snowshoe Group. Field relations suggest that this was probably coeval with the mid-Paleozoic emplacement of the Boss Mountain gneiss. Metamorphism during the Jurassic was synchronous with F2 deformation in rocks of the Snowshoe Group, and resulted in Barrovian type mineral assemblages ranging from the biotite through sillimanite zones. The metamorphic grade increases from west to east; with only low grade metamorphism of the cover rocks in the study area. Phase 2 structures in the Snowshoe Group were overprinted by the peak of this metamorphic event, as indicated by staurolite through sillimanite zone assemblages. The Boss Mountain area is structurally correlative with rocks of the Shuswap Complex. These rocks appear to comprise a portion of the continental margin sedimentary wedge, which was overridden by an allochthonous terrane accreted to the western margin of North America in post-Early Jurassic times.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat