Nucleon structure at large x: nuclear effects in deuterium

I review quark momentum distributions in the nucleon at large momentum fractions x. Particular attention is paid to the impact of nuclear effects in deuterium on the d/u quark distribution ratio as x -> 1. A new global study of parton distributions, using less restrictive kinematic cuts in Q^2 and W^2, finds strong suppression of the d quark distribution once nuclear corrections are accounted for.Comment: to appear in Achievements and New Directions in Subatomic Physics: Festschrift in Honour of Tony Thomas' 60th Birthday, Adelaide, Australia, 15-19 Feb. 2010, ed. W. Melnitchou

Quark-hadron duality in electron-pion scattering

We explore the relationship between exclusive and inclusive electromagnetic scattering from the pion, focusing on the transition region at intermediate Q^2. Combining Drell-Yan data on the leading twist quark distribution in the pion with a model for the resonance region at large x, we calculate QCD moments of the pion structure function over a range of Q^2, and quantify the role of higher twist corrections. Using a parameterization of the pion elastic form factor and phenomenological models for the pi -> rho transition form factor, we further test the extent to which local duality may be valid for the pion.Comment: 23 pages, 7 figures, to appear in Eur. J. Phys.

QCD and the Structure of the Nucleon in Electron Scattering

The internal structure of the nucleon is discussed within the context of QCD. Recent progress in understanding the distribution of flavor and spin in the nucleon is reviewed, and prospects for extending our knowledge of nucleon structure in electron scattering experiments at modern facilities such as Jefferson Lab are outlined.Comment: 52 pages, 11 figures, lectures presented at the 1999 Hampton University Graduate Studies (HUGS) summer school, Jefferson La

D0 Search for the Higgs Boson in Multijet Events

We present two searches for the Higgs boson in \sqrt{s} = 1.96 TeV p\bar{p}collisions using data taken with the \dz detector during Run II of the Fermilab Tevatron collider. The first study is a search for neutral Higgs bosons produced in association with bottom quarks. We set upper limits on the production of neutral Higgs bosons in the mass range of 90 to 150 GeV.The second study is a search for the standard model Higgs boson produced in association with the Z boson. We study the p\bar{p}\to ZH \to \nu \bar{\nu} b \bar{b} channel, which is one of the most sensitive ways to search for light Higgs bosons at the Tevatron. We search for a peak in invariant mass distribution of two b-tagged jets. After subtracting the backgrounds, we set the 95% C.L. upper limits on the \sigma(p\bar{p} \to ZH \to \nu \bar{\nu}) \times BR(H) \to b\bar{b}) for Higgs masses between 105 and 135 GeV.Comment: 3 pages, 2 figures, PANIC2005, to be published in AIP proceeding

Flavor Asymmetries in the Proton and Semi-Inclusive Processes

Semi-inclusive electron scattering provides a powerful tool with which to study the spin and flavor distributions in the proton. Greater kinematic coverage at the proposed Electron-Polarized Ion Collider facility will enable the valence d/u ratio to be determined at large x through pion production. At small x, pion production can be used to extract the d-bar/u-bar ratio, complementing existing semi-inclusive measurements by HERMES, and Drell-Yan data from Fermilab. Asymmetries in heavier quark flavors can also be probed by tagging strange and charm hadrons in the final state.Comment: 15 pages, 6 figures, presented at the Electron-Polarized Ion Collider Workshop, IUCF, April 199

Neutron Structure Function and A=3 Mirror Nuclei

We investigate deep inelastic scattering from He-3 and H-3 within a conventional convolution treatment of binding and Fermi motion effects. Using realistic Faddeev wave functions together with a nucleon spectral function, we demonstrate that the free neutron structure function can be extracted in deep-inelastic scattering from A=3 mirror nuclei, with nuclear effects canceling to within 2% for x < 0.85.Comment: 13 pages, 4 figures, version to appear in Phys. Lett.

Deuteron spin structure functions in the resonance and DIS regions

We derive relations between spin-dependent nuclear and nucleon g_1 and g_2 structure functions within the nuclear impulse approximation, which are valid at all Q^2, and in both the resonance and deep inelastic regions. We apply the formalism to the specific case of the deuteron, which is often used as a source of neutron structure information, and compare the size of the nuclear corrections calculated using exact kinematics and using approximations applicable at large Q^2.Comment: 22 pages, 7 figures, Fig. 1 correcte

Spin structure functions of 3He at finite Q^2

Using recently derived relations between spin-dependent nuclear and nucleon g_1 and g_2 structure functions at finite Q^2, we study nuclear effects in 3He in the nucleon resonance and deep inelastic regions. Comparing the finite-Q^2 results with the standard convolution formulas obtained in the large-Q^2 limit, we find significant broadening of the effective nucleon momentum distribution functions, leading to additional suppression of the nuclear g_1 and g_2 structure functions around the resonance peaks.Comment: 33 pages, 6 figures, to appear in Phys. Rev.