The analysis of the nine 1-fold differential cross sections for the γr,vp→π+π−p photo- and electroproduction reactions obtained with the CLAS detector at Jefferson Laboratory was carried out with the ...goal to establish the contributing resonances in the mass range from 1.6 GeV to 1.8 GeV. In order to describe the photo- and electroproduction data with Q2-independent resonance masses and hadronic decay widths in the Q2 range below 1.5 GeV2, it was found that an N′(1720)3/2+ state is required in addition to the already well-established nucleon resonances. This work demonstrates that the combined studies of π+π−p photo- and electroproduction data are vital for the observation of this resonance. The contributions from the N′(1720)3/2+ state and the already established N(1720)3/2+ state with a mass of 1.745 GeV are well separated by their different hadronic decays to the πΔ and ρp final states and the different Q2-evolution of their photo-/electroexcitation amplitudes. The N′(1720)3/2+ state is the first recently established baryon resonance for which the results on the Q2-evolution of the photo-/electrocouplings have become available. These results are important for the exploration of the nature of the “missing” baryon resonances.
The physics of the gravitational form factors of the proton, as well as their understanding within quantum chromodynamics, has advanced significantly in the past two decades through both theory and ...experiment. This Colloquium provides an overview of this progress, highlights the physical insights unveiled by studies of gravitational form factors, and reviews their interpretation in terms of the mechanical properties of the proton.
Performance of the CLAS12 Silicon Vertex Tracker modules Antonioli, M.A.; Boiarinov, S.; Bonneau, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2013, Volume:
732
Journal Article
Peer reviewed
Open access
For the 12GeV upgrade, the CLAS12 experiment has designed a Silicon Vertex Tracker (SVT) using single sided microstrip sensors fabricated by Hamamatsu. The sensors have graded angle design to ...minimize dead areas and a readout pitch of 156μm, with intermediate strip. Double sided SVT module hosts three daisy-chained sensors on each side with a full strip length of 33cm. There are 512 channels per module read out by four Fermilab Silicon Strip Readout (FSSR2) chips featuring data driven architecture, mounted on a rigid-flex hybrid. Modules are assembled on the barrel using unique cantilevered geometry to minimize the amount of material in the tracking volume. Design and performance of the SVT modules are presented, focusing on results of electrical measurements.
•A Silicon Vertex Tracker has been designed for the central tracker of the CLAS12 experiment.•Using cantilevered module geometry allows minimizing amount of material in the tracking volume.•A dedicated Hybrid Flex Circuit Board has been developed to read out double sided module.•Module performance meets design goals of the CLAS12 Central Tracker.
Hadron physics has been an essential part of the physics program with the CLAS detector in experimental hall B at Thomas Jefferson National Accelerator Facility (Jefferson Lab). With the 12 GeV ...upgrade of the CEBAF machine, hadron physics in Hall B will be extended to a new domain of higher mass resonances and the range of higher transferred momentum using up to 11 GeV electron beams and the upgraded CLAS12 detector. In this paper, status of the hall B superconducting magnets for the 12 GeV upgrade is presented.
A new highly segmented start counter for the CLAS detector Sharabian, Y.G.; Battaglieri, M.; Burkert, V.D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2006, 2006-1-00, Volume:
556, Issue:
1
Journal Article
Peer reviewed
Open access
The design, construction and performance of a highly segmented Start Counter are described. The Start Counter is an integral part of the trigger used in photon beam running with CLAS in Hall B at the ...Thomas Jefferson National Accelerator Facility (TJNAF). The Start Counter is constructed of 24 2.2-mm-thick single-ended scintillation paddles, forming a hermetic hexagon around the target region. This device measures the interaction time of the incoming photon in the target by detecting the outgoing particles. The counter provides complex trigger topologies, shows good efficiency and achieved a time resolution of 350
ps.
Momentum sharing in imbalanced Fermi systems Hen, O.; Sargsian, M.; Weinstein, L. B. ...
Science (American Association for the Advancement of Science),
10/2014, Volume:
346, Issue:
6209
Journal Article
Peer reviewed
Open access
The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of ...fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using 12C, 27Al, 56Fe, and 208Pb targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin–state, ultracold atomic gas systems.
Recent results from the Deeply Virtual Compton Scattering (DVCS) program at Jefferson Lab will be presented. Approved dedicated DVCS experiments at 6 GeV and plans for the 12 GeV upgrade will be ...discussed.
Hadron physics has been an essential part of the physics program with the CLAS detector in experimental hall B at Thomas Jefferson National Accelerator Facility (Jefferson Lab). With the 12 GeV ...upgrade of the CEBAF machine, hadron physics in Hall B will be extended to a new domain of higher mass resonances and the range of higher transferred momentum using up to 11 GeV electron beams and the upgraded CLAS12 detector. In this paper, status of the hall B superconducting magnets for the CLAS12 detector is presented.
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