| 1. |
- Alcorn, J, et al.
(författare)
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Basic instrumentation for Hall A at Jefferson Lab
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 522:3, s. 294-346
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Dutta, D, et al.
(författare)
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Nuclear transparency with the gamma n ->pi(-)p process in He-4
- 2003
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 68:2: 021001
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the nuclear transparency of the fundamental process gamman-->pi(-)p in He-4. These measurements were performed at Jefferson Lab in the photon energy range of 1.6-4.5 GeV and at theta(cm)(pi)=70degrees and 90degrees. These measurements are the first of their kind in the study of nuclear transparency in photoreactions. They also provide a benchmark test of Glauber calculations based on traditional models of nuclear physics. The transparency results suggest deviations from the traditional nuclear physics picture. The momentum transfer dependence of the measured nuclear transparency is consistent with Glauber calculations that include the quantum chromodynamics phenomenon of color transparency.
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| 3. |
- Zhu, LY, et al.
(författare)
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Cross-section measurement of charged-pion photoproduction from hydrogen and deuterium
- 2003
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Ingår i: Physical Review Letters. - 1079-7114. ; 91:2: 022003
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the differential cross section for the gamman-->pi(-)p and gammap-->pi(+)n reactions at theta(c.m.)=90degrees in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at E(gamma)greater than or similar to3.3 GeV exhibit a global scaling behavior for both pi(-) and pi(+) photoproduction, consistent with the constituent counting rule and the existing pi(+) photoproduction data. Possible oscillations around the scaling value are suggested by these new data. The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive pi(-) to pi(+) photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.
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| 4. |
- Waligórski, M P R, et al.
(författare)
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Cellular parameters for track structure modeling of radiation hazard in space.
- 2004
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Ingår i: Adv Space Res. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 34:6, s. 1378-82
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Tidskriftsartikel (refereegranskat)abstract
- Based on irradiation with 45 MeV/u N and B ions and with Co-60 c rays, cellular parameters of Katz’s track structure modelhave been fitted for the survival of V79-379A Chinese hamster lung fibroblasts. Cellular parameters representing neoplastictransformations in C3H10T/1/2 cells after their irradiation with heavy ion beams, taken from earlier work, were also used to modelthe radiation hazard in deep space, following the system for evaluating, summing and reporting occupational exposures proposed in1967 by a subcommittee of NCRP. We have performed model calculations of the number of transformations in surviving cells, aftera given fluence of heavy charged particles of initial energy 500 MeV/u, penetrating thick layers of cells. We take the product of celltransformation and survival probabilities, calculated along the path lengths of charged particles using cellular survival and transformationparameters, to represent a quantity proportional to the ‘‘radiation risk factor’’ discussed in the NCRP document. The‘‘synergistic’’ effect of simultaneous charged particle transfers is accounted for by the ‘‘track overlap’’ mode inherent in the model ofKatz.
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