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 present a search at the Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling α' to electrons. Such a particle A' can be produced in electron-nucleus fixed-target scattering and then decay to an e + e- pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175-250 MeV, found no evidence for an A'→ e+ e- reaction, and set an upper limit of α'/α ~/= 10(-6). Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.
The 1987 amendments to the Older Americans Act mandate a special effort to serve low-income minority elderly persons. A literature review showed that "practice-oriented" research on service use has focused primarily on identifying barriers with much less attention to identification of strategies for overcoming the barriers. This paper identifies and describes strategies used throughout Texas. Strategies addressing the "lack of knowledge" barrier included use of influential groups, working with significant individuals, and the media. Strategies addressing the "lack of access" barrier included transportation, affordability, and availability. Strategies addressing the "lack of intent" barrier focused on cultural differences, making services attractive, and overcoming negative attitudes toward service use.
An experimental study of the 16 O(e, e ′ K + ) 16 Λ N reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e, e ′ K + )Λ,Σ 0 exclusive reactions and a precise calibration of the energy scale. A groundstate binding energy of 13.76 ± 0.16 MeV was obtained for 16 Λ N with better precision than previous measurements on the mirror hypernucleus 16 Λ O. Precise energies have been determined for peaks arising from a Λ in s and p orbits coupled to the p 1/2 and p 3/2 hole states of the 15 N core nucleus.
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