The unpolarized and polarized Beam Charge Asymmetries (BCAs) of the
e
→
±
p
→
e
±
p
γ
process off unpolarized hydrogen are discussed. The measurement of BCAs with the CLAS12 spectrometer at the ...Thomas Jefferson National Accelerator Facility, using polarized positron and electron beams at 10.6 GeV is investigated. This experimental configuration allows to measure azimuthal and
t
-dependences of the unpolarized and polarized BCAs over a large
(
x
B
,
Q
2
)
phase space, providing a direct access to the real part of the Compton Form Factor (CFF)
H
. Additionally, these measurements confront the Bethe-Heitler dominance hypothesis and eventual effects beyond leading twist. The impact of potential positron beam data on the determination of CFFs is also investigated within a local fitting approach of experimental observables. Positron data are shown to strongly reduce correlations between CFFs and consequently improve significantly the determination of
R
e
H
.
Transition to Perturbative QCD Gilman, R; Holt, R J; Stoler, P
Journal of physics. Conference series,
05/2011, Letnik:
299, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We review the Jefferson Lab program concerning the interplay between hadronic and underlying quark degrees of freedom in exclusive reactions. Much of the program was initially based on predictions ...from perturbative QCD (pQCD) concerning scaling of reaction cross sections, helicity conservation, and asymptotic behavior of form factors. Although much of the data do not follow simple pQCD expectations, some observables scale better than expected. Generally, the underlying dynamics are best understood with nonperturbative quark models, but the elastic deuteron form factors provide an example of the success of hadronic models to high momentum transfer.
The CLAS Cherenkov detector Adams, G.; Burkert, V.; Carl, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2001, Letnik:
465, Številka:
2
Journal Article
Recenzirano
The design, construction, and performance of the CLAS Cherenkov threshold gas detector at Jefferson Lab is described. The detector consists of 216 optical modules. Each module consists of three ...adjustable mirrors of lightweight composite construction, a Winston light collecting cone, a 5-in. photomultiplier tube, and specially designed magnetic shielding. Efficiencies and response functions have been measured.
The CLAS12 high threshold Cherenkov counter Sharabian, Y.G.; Burkert, V.D.; Biselli, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2020, Letnik:
968, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The High Threshold Cherenkov Counter (HTCC) is one of the detector systems of the CLAS12 spectrometer, and is used to generate a fast trigger signal in electron scattering experiments in the polar ...angle range from 5°to 35°. The HTCC is installed in front of the drift chambers and introduces a minimal amount of additional material within the acceptance. The HTCC is one unit whose core component is a multifocal mirror that consists of 60 lightweight ellipsoidal mirrors. It is important that the HTCC provides efficient coverage of the CLAS12 forward acceptance with no gaps. In order to achieve this, each sector of the CLAS12 Forward Detector is covered by 2 identical half-sector mirrors that focus Cherenkov light on 8 phototubes. The HTCC has a total of 48 channels with Electron Tubes 9823QKB photomultipliers that have a 5-in quartz face plate to detect Cherenkov light. The system provides rejection of charged π-mesons with momenta below 4.8 GeV for the reliable identification of scattered electrons. In this paper the details of the design, construction, calibration, and performance results of the HTCC are presented.
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