The performance of the GlueX Forward Calorimeter was studied using a small version of the detector and a variable energy electron beam derived from the Hall B tagger at Jefferson Lab. For electron ...energies from 110MeV to 260MeV, which are near the lower-limits of the design sensitivity, the fractional energy resolution was measured to range from 20% to 14%, which meets the design goals. The use of custom 250MHz flash ADCs for readout allowed precise measurements of signal arrival times. The detector achieved timing resolutions of 0.38ns for a single 100mV pulse, which will allow timing discrimination of photon beam bunches and out-of-time background during the operation of the GlueX detector.
•A beam test was conducted for a miniature of the GlueX Forward Calorimeter.•The energy resolution at low energies was found to be consistent with design goals.•The timing resolution of the incidence of events was measured with flash ADCs.•The timing resolution was confirmed to be adequate for discriminating beam bunches.
The CLAS forward electromagnetic calorimeter Amarian, M.; Asryan, G.; Beard, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2001, Volume:
460, Issue:
2
Journal Article
Peer reviewed
Open access
The CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab utilizes six iron-free superconducting coils to provide an approximately toroidal magnetic field. The six sectors are instrumented ...individually to form six independent spectrometers. The forward region (8°<
θ<45°) of each sector is equipped with a lead–scintillator electromagnetic sampling calorimeter (EC), 16
radiation lengths thick, using a novel triangular geometry with stereo readout. With its good energy and position resolution, the EC is used to provide the primary electron trigger for CLAS. It is also used to reject pions, reconstruct π° and η decays and detect neutrons. This paper treats the design, construction and performance of the calorimeter.
The Heavy Photon Search experiment took its first data in a 2015 engineering run using a 1.056 GeV, 50 nA electron beam provided by CEBAF at the Thomas Jefferson National Accelerator Facility, ...searching for a prompt, electroproduced dark photon with a mass between 19 and 81 MeV/c2. A search for a resonance in the e+e− invariant mass distribution, using 1.7 days (1170 nb−1) of data, showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the standard model photon are set at the level of 6×10−6. Future runs with higher luminosity will explore new territory.
The time-of-flight system for CLAS Smith, E.S.; Carstens, T.; Distelbrink, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/1999, Volume:
432, Issue:
2-3
Journal Article
Peer reviewed
Open access
The time of flight system for the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility is described. The system, covering an area of 206 m2, is composed of ...scintillation counters 5.08 cm thick, 15 and 22 cm wide, and lengths which vary from 32 cm at the most forward angle to 450 cm at larger angles. All of the components of the system have been designed to optimize the time resolution. Event timing, achieved by leading-edge discrimination with time-walk correction, has been measured with cosmic rays, a laser pulser, and known particle interactions. The intrinsic time resolution varies from about 80 ps for the short counters to 160 ps for the longer counters. Reconstruction of interacting particles during the first period of operation yields an average time resolution for electrons of 163 ps.
A new electromagnetic calorimeter consisting of 140 lead tungstate (PbWO4) scintillating crystals was constructed for the PrimEx-η experiment at Jefferson lab. The calorimeter was integrated into the ...data acquisition and trigger systems of the GlueX detector and used in the experiment to reconstruct Compton scattering events. The experiment started collecting data in the spring of 2019 and acquired about 30% of the required statistics. The calorimeter is a prototype for two PbWO4-based detectors: the Neutral Particle Spectrometer (NPS) and the lead tungstate insert of the Forward CALorimeter (FCAL) of the GlueX detector. The article presents the design and performance of the Compton calorimeter and gives a brief overview of the FCAL and NPS projects.
A new electromagnetic calorimeter consisting of 140 lead tungstate (PbWO4) scintillating crystals was constructed for the PrimEx- η experiment at Jefferson lab. The calorimeter was integrated into ...the data acquisition and trigger systems of the GlueX detector and used in the experiment to reconstruct Compton scattering events. The experiment started collecting data in the spring of 2019 and acquired about 30% of the required statistics. The calorimeter is a prototype for two PbWO4-based detectors: the Neutral Particle Spectrometer (NPS) and the lead tungstate insert of the Forward CALorimeter (FCAL) of the GlueX detector. The article presents the design and performance of the Compton calorimeter and gives a brief overview of the FCAL and NPS projects.
The Heavy Photon Search beamline and its performance Baltzell, N.; Egiyan, H.; Ehrhart, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2017, Volume:
859, Issue:
C
Journal Article
Peer reviewed
Open access
The Heavy Photon Search (HPS) is an experiment to search for a hidden sector photon, aka a heavy photon or dark photon, in fixed target electroproduction at the Thomas Jefferson National Accelerator ...Facility (JLab). The HPS experiment searches for the e+e− decay of the heavy photon with bump hunt and detached vertex strategies using a compact, large acceptance forward spectrometer, consisting of a silicon microstrip detector (SVT) for tracking and vertexing, and a PbWO4 electromagnetic calorimeter for energy measurement and fast triggering. To achieve large acceptance and good vertexing resolution, the first layer of silicon detectors is placed just 10cm downstream of the target with the sensor edges only 500μm above and below the beam. Placing the SVT in such close proximity to the beam puts stringent requirements on the beam profile and beam position stability. As part of an approved engineering run, HPS took data in 2015 and 2016 at 1.05GeV and 2.3GeV beam energies, respectively. This paper describes the beam line and its performance during that data taking.
The heavy photon search experiment (HPS) at the Thomas Jefferson National Accelerator Facility searches for electroproduced dark photons. We report results from the 2016 engineering run consisting of ...10 608 nb–1 of data for both the prompt and displaced vertex searches. A search for a prompt resonance in the e+e– invariant mass distribution between 39 and 179 MeV showed no evidence of dark photons above the large QED background, limiting the coupling of ε2≳10–5, in agreement with previous searches. The search for displaced vertices showed no evidence of excess signal over background in the masses between 60 and 150 MeV, but had insufficient luminosity to limit canonical heavy photon production. This is the first displaced vertex search result published by HPS. HPS has taken high-luminosity data runs in 2019 and 2021 that will explore new dark photon phase space.
The Heavy Photon Search test detector Battaglieri, M.; Boyarinov, S.; Bueltmann, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2015, Volume:
777, Issue:
C
Journal Article
Peer reviewed
Open access
The Heavy Photon Search (HPS), an experiment to search for a hidden sector photon in fixed target electroproduction, is preparing for installation at the Thomas Jefferson National Accelerator ...Facility (JLab) in the Fall of 2014. As the first stage of this project, the HPS Test Run apparatus was constructed and operated in 2012 to demonstrate the experiment׳s technical feasibility and to confirm that the trigger rates and occupancies are as expected. This paper describes the HPS Test Run apparatus and readout electronics and its performance. In this setting, a heavy photon can be identified as a narrow peak in the e+e− invariant mass spectrum above the trident background or as a narrow invariant mass peak with a decay vertex displaced from the production target, so charged particle tracking and vertexing are needed for its detection. In the HPS Test Run, charged particles are measured with a compact forward silicon microstrip tracker inside a dipole magnet. Electromagnetic showers are detected in a PbW04 crystal calorimeter situated behind the magnet, and are used to trigger the experiment and identify electrons and positrons. Both detectors are placed close to the beam line and split top-bottom. This arrangement provides sensitivity to low-mass heavy photons, allows clear passage of the unscattered beam, and avoids the spray of degraded electrons coming from the target. The discrimination between prompt and displaced e+e− pairs requires the first layer of silicon sensors be placed only 10cm downstream of the target. The expected signal is small, and the trident background huge, so the experiment requires very large statistics. Accordingly, the HPS Test Run utilizes high-rate readout and data acquisition electronics and a fast trigger to exploit the essentially 100% duty cycle of the CEBAF accelerator at JLab.
The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the ...fall of 2018 with the CLAS12 spectrometer using a 10.6 GeV longitudinally spin-polarized electron beam delivered by CEBAF at JLab. The measured asymmetries provide the first opportunity to extract the parton distribution function e(x), which provides information about the interaction between gluons and quarks, in a collinear framework that offers cleaner access than previous measurements. The asymmetries also constitute the first ever signal sensitive to the helicity-dependent two-pion fragmentation function G1⊥. A clear sign change is observed around the ρ mass that appears in model calculations and is indicative of the dependence of the produced pions on the helicity of the fragmenting quark.
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