The bremsstrahlung tagged photon beam in Hall B at JLab Sober, D.I.; Crannell, Hall; Longhi, Alberto ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2000, Volume:
440, Issue:
2
Journal Article
Peer reviewed
We describe the design and commissioning of the photon tagging beamline installed in experimental Hall B at the Thomas Jefferson National Accelerator Facility (JLab). This system can tag photon ...energies over a range from 20% to 95% of the incident electron energy, and is capable of operation with beam energies up to 6.1
GeV. A single dipole magnet is combined with a hodoscope containing two planar arrays of plastic scintillators to detect energy-degraded electrons from a thin bremsstrahlung radiator. The first layer of 384 partially overlapping small scintillators provides photon energy resolution, while the second layer of 61 larger scintillators provides the timing resolution necessary to form a coincidence with the corresponding nuclear interaction triggered by the tagged photon. The definitions of overlap channels in the first counter plane and of geometric correlation between the two planes are determined using digitized time information from the individual counters. Auxiliary beamline devices are briefly described, and performance results to date under real operating conditions are presented. The entire photon-tagging system has met or exceeded its design goals.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The first measurements of the transferred polarization for the exclusive {rvec e}p {yields} e{prime}K{sup +}{rvec {Lambda}} reaction have been performed in Hall B at the Thomas Jefferson National ...Accelerator Facility using the CLAS spectrometer. A 2.567 GeV electron beam was used to measure the hyperon polarization over a range of Q{sup 2} from 0.3 to 1.5 (GeV/c){sup 2}, W from 1.6 to 2.15 GeV, and over the full center-of-mass angular range of the K{sup +} meson. Comparison with predictions of hadrodynamic models indicates strong sensitivity to the underlying resonance contributions. A non-relativistic quark model interpretation of our data suggests that the s{bar s} quark pair is produced with spins predominantly anti-aligned. Implications for the validity of the widely used {sup 3}P{sub o} quark-pair creation operator are discussed.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Differential cross sections for the reaction {gamma}p{yields}{eta}{sup '}p have been measured with the CLAS spectrometer and a tagged photon beam with energies from 1.527 to 2.227 GeV. The results ...reported here possess much greater accuracy than previous measurements. Analyses of these data suggest for the first time the coupling of the {eta}{sup '}N channel to both the S{sub 11}(1535) and P{sub 11}(1710) resonances, known to couple strongly to the {eta}N channel in photoproduction on the proton, and the importance of J=3/2 resonances in the process.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
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