The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro-and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2 x 10(-4). A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10(38) CM-2 s(-1). The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium. (C) 2003 Elsevier B.V. All rights reserved

We have measured parity-violating asymmetries in elastic electron-proton scattering over the range of momentum transfers 0.12 < or =Q2 < or =1.0 GeV2. These asymmetries, arising from interference of the electromagnetic and neutral weak interactions, are sensitive to strange-quark contributions to the currents of the proton. The measurements were made at Jefferson Laboratory using a toroidal spectrometer to detect the recoiling protons from a liquid hydrogen target. The results indicate nonzero, Q2 dependent, strange-quark contributions and provide new information beyond that obtained in previous experiments.

We have measured parity-violating asymmetries in elastic electron-proton and quasi-elastic electron-deuteron scattering at Q 2 = 0.22 and 0.63 GeV 2 . They are sensitive to strange quark contributions to currents in the nucleon, and to the nucleon axial current. The results indicate strange quark contributions of < ∼ 10% of the charge and magnetic nucleon form factors at these four-momentum transfers. We also present the first measurement of anapole moment effects in the axial current at these four-momentum transfers.PACS numbers: 11.30. Er, 14.20.Dh, 25.30.Bf At short distance scales, bound systems of quarks have relatively simple properties and QCD is successfully described by perturbation theory. However, on the size scale of the bound state, ∼ 1 fm, the QCD coupling constant is large and the effects of the color fields are a significant challenge, even in lattice QCD. In addition to valence quarks, e.g., uud for the proton, there is a sea of gluons and qq pairs that plays an important role. From a series of experiments measuring the parity-violating asymmetries of electrons scattered from protons and neutrons, we can extract the contributions of strange quarks to nucleon ground state charge and magnetic form factors. These strange quark contributions are exclusively part of the quark sea because there are no strange valence quarks in the nucleon. experiments have previously reported measurements of these parity-violating asymmetries. Using the combined forward angle asymmetries and the SAMPLE backward angle proton and deuteron measurements, a complete experimental determination of the strange quark vector currents and the axial current (see discussion below) has been made at a four-momentum transfer Q 2 = 0.1 GeV 2 [5]. In this paper, we report the first complete backward angle asymmetry measurements since the SAMPLE experiment, at the four-momentum transfers

Tensor polarization observables (t 20 , t 21 , and t 22 ) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 ͑GeV͞c͒ 2 . The experiment was performed at the Jefferson Laboratory in Hall C using the electron High Momentum Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q 2 the deuteron charge form factors G C and G Q . They are in good agreement with relativistic calculations and disagree with perturbative QCD predictions.

A rigorous extraction of the deuteron charge form factors from tensor polarization data in elastic electron-deuteron scattering, at given values of the 4-momentum transfer, is presented. Then the world data for elastic electron-deuteron scattering is used to parameterize, in three different ways, the three electromagnetic form factors of the deuteron in the 4-momentum transfer range 0-7 fm −1 . This procedure is made possible with the advent of recent polarization measurements. The parameterizations allow a phenomenological characterization of the deuteron electromagnetic structure. They can be used to remove ambiguities in the form factors extraction from future polarization data.