We measured the triple coincidence A(e,e^{'}np) and A(e,e^{'}pp) reactions on carbon, aluminum, iron, and lead targets at Q^{2}>1.5 (GeV/c)^{2}, x_{B}>1.1 and missing momentum >400 MeV/c. This was ...the first direct measurement of both proton-proton (pp) and neutron-proton (np) short-range correlated (SRC) pair knockout from heavy asymmetric nuclei. For all measured nuclei, the average proton-proton (pp) to neutron-proton (np) reduced cross-section ratio is about 6%, in agreement with previous indirect measurements. Correcting for single-charge exchange effects decreased the SRC pairs ratio to ∼3%, which is lower than previous results. Comparisons to theoretical generalized contact formalism (GCF) cross-section calculations show good agreement using both phenomenological and chiral nucleon-nucleon potentials, favoring a lower pp to np pair ratio. The ability of the GCF calculation to describe the experimental data using either phenomenological or chiral potentials suggests possible reduction of scale and scheme dependence in cross-section ratios. Our results also support the high-resolution description of high-momentum states being predominantly due to nucleons in SRC pairs.
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, Volume:
968, Issue:
C
Journal Article
Peer reviewed
Open access
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.
The cross section of atomic electron Compton scattering γ+e→γ′+e′ was measured in the 4.400–5.475 GeV photon beam energy region by the PrimEx collaboration at Jefferson Lab with an accuracy of 2.6% ...and less. The results are consistent with theoretical predictions that include next-to-leading order radiative corrections. The measurements provide the first high precision test of this elementary QED process at beam energies greater than 0.1 GeV.
First results from the longitudinally polarized frozen-spin target (FROST) program are reported. The double-polarization observable E, for the reaction γ→p→→π+n, has been measured using a circularly ...polarized tagged-photon beam, with energies from 0.35 to 2.37 GeV. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer in Hall B at the Thomas Jefferson National Accelerator Facility. These polarization data agree fairly well with previous partial-wave analyses at low photon energies. Over much of the covered energy range, however, significant deviations are observed, particularly in the high-energy region where high-L multipoles contribute. The data have been included in new multipole analyses resulting in updated nucleon resonance parameters. We report updated fits from the Bonn–Gatchina, Jülich–Bonn, and SAID groups.
A large area ring-imaging Cherenkov detector has been designed to provide clean hadron identification capability in the momentum range from 3 GeV/c to 8 GeV/c for the CLAS12 experiments at the ...upgraded 12 GeV continuous electron beam accelerator facility of Jefferson Lab to study the 3D nucleon structure in the yet poorly explored valence region by deep-inelastic scattering, and to perform precision measurements in hadronization and hadron spectroscopy. The adopted solution foresees a novel hybrid optics design based on an aerogel radiator, composite mirrors and densely packed and highly segmented photon detectors. Cherenkov light will either be imaged directly (forward tracks) or after two mirror reflections (large angle tracks). The preliminary results of individual detector component tests and of the prototype performance at test-beams are reported here.
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A large-area ring-imaging Cherenkov detector has been designed to provide clean hadron identification capability in the momentum range from 3GeV/
c
up to 8GeV/
c
for the CLAS12 experiment at the ...upgraded 12GeV continuous electron beam accelerator facility of Jefferson Laboratory. The adopted solution foresees a novel hybrid optics design based on aerogel radiator, composite mirrors and highly packed and highly segmented photon detectors. Cherenkov light will either be imaged directly (forward tracks) or after two mirror reflections (large-angle tracks). We report here the results of the tests of a large-scale prototype of the RICH detector performed with the hadron beam of the CERN T9 experimental hall for the direct detection configuration. The tests demonstrated that the proposed design provides the required pion-to-kaon rejection factor of 1 : 500 in the whole momentum range.
The CLAS12 Trigger System Raydo, B.; Boyarinov, S.; Celentano, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Volume:
960, Issue:
C
Journal Article
Peer reviewed
Open access
This article describes the CLAS12 Trigger System. The simulation, hardware, and software design, as well as all validation procedures, are discussed. The firmware development tools used are discussed ...as well, including our experience with VIVADO High Level Synthesis.
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