Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session JF: Instrumentation II |
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Chair: Donal Day, University of Virginia Room: Lamy |
Friday, October 30, 2015 10:30AM - 10:42AM |
JF.00001: Construction and testing of the tracking drift chambers for the SHMS spectrometer in Jefferson Lab Hall C Debaditya Biswas The super high momentum spectrometer (SHMS) is being constructed as a crucial part standard equipment for the planned physics program in Jefferson lab experimental Hall C as the part of the energy doubling the available beam energy to 12 GeV. The SHMS will be used to track scattered particles after the beam collides with a fixed target to determine to determine the energy and the scattering angles at the collision vertex.The Hampton University group was responsible for the design, construction, and testing of the main tracking drift chambers for the SHMS detector package. The basic working principles, design considerations, construction, and testing of the chambers will be discussed. [Preview Abstract] |
Friday, October 30, 2015 10:42AM - 10:54AM |
JF.00002: Jefferson Lab Hall A Beamline Instrumentation and Calibration for GMP experiment Thir Narayan Gautam The nucleon electromagnetic form factors characterize the distributions of electric charge and magnetization current inside the nucleon and thus reflect the internal structure determined by Quantum Chromodynamics. The GMp experiment is a first experiment run in Hall A at Jefferson Lab after the upgrade to double the beam energy with the goal to precisely measure electron-proton elastic cross section in the $\rm Q^{2}$ range of 7 to 17~$\rm GeV^{2}$ with an accuracy of better than 2\%; several time better than existing data at the highest $\rm Q^{2}$. In order to achieve this accuracy, a determination of the accumulated beam charge of better than 0.5\% is required. The new 12~GeV beamline was commissioned during the spring of 2015, with the main instrumentation consisting of beam charge and position monitors. In this talk, the procedures and the results of the calibrations of these beamline components will be presented. [Preview Abstract] |
Friday, October 30, 2015 10:54AM - 11:06AM |
JF.00003: Thermal Annealing in Calorimetery for Super Bigbite Seamus Riordan, Bogdan Wojtsekhowski, Mark Jones, Albert Shahinyan Radiation damage to lead glass in the form of optical darkening presents a serious challenge to electromagnetic calorimetry for modern high-luminosity experiments in an open environment. In particular, the Super Bigbite $G_E^p$ measurement to $Q^2=12~\mathrm{GeV}^2$ using $ep$ scattering at Jefferson Lab relies heavily on calorimetry in such an environment for elastic electron event triggering and event reconstruction. The novel technique of thermal annealing to maintain continuous optical transparency of the lead glass calorimeter blocks has been chosen to remedy this effect. An overview of the technical design considerations for such a calorimeter and results regarding the construction of smaller-scale prototypes will be presented. [Preview Abstract] |
Friday, October 30, 2015 11:06AM - 11:18AM |
JF.00004: Plans for Precision M{\o}ller Polarimetry in Hall~A at Jefferson Lab Jim Napolitano M{\o}ller scattering has long been a useful tool for measuring high energy electron beam polarization, because the cross section and analyzing power are perfectly calculable in QED. High permeability ferromagnetic foils targets are historically used as polarized electron targets, but germane magnetic properties of the alloy limit the ultimate precision to a few percent. Pure iron targets have been used, however, to increase precision. This talk will describe plans for ``high field'' pure iron polarimetry in Hall~A at JLab. The system includes a target mechanism that allows us to demonstrate iron saturation behavior and a spectrometer system for separating backgrounds and reducing sensitivity to the Levchuk Effect. [Preview Abstract] |
Friday, October 30, 2015 11:18AM - 11:30AM |
JF.00005: Calibration of the Tagger Detectors with GlueX Commissioning Data Alexander Barnes, Nathan Sparks The GlueX experiment at Jefferson Lab uses a linearly polarized photon beam to search for mesons with gluonic excitations and measure their spectrum and couplings. This polarized photon beam will be created using a 12 GeV electron beam incident on a 20 $\mu$m thick diamond radiator, where it undergoes coherent bremsstrahlung to produce an intensity enhancement in the region of 9 GeV with a linear polarization around 40$\%$. The energy of the photon is inferred by analyzing the post-bremsstrahlung electron energy in the tagging spectrometer. A highly segmented tagging detector called the tagger microscope will intercept the electrons in the region of the coherent peak 8.4-9.0 GeV photon energy. These electrons are incident on a two-dimensional array of scintillating fibers which are read out using multi-photon pixel counters (MPPC). Post-bremsstrahlung electrons outside of the coherent peak region corresponding to photon energies of 3.0-11.8 GeV are incident on a hodoscope of plastic scintillators which are read out by photomultiplier tubes (PMT). The calibration results for the tagger microscope and hodoscope using commissioning data will be presented. [Preview Abstract] |
Friday, October 30, 2015 11:30AM - 11:42AM |
JF.00006: Calibrations for Charged Particle Tracking with the GlueX Detector Michael Staib Two gas detectors comprise the tracking system for the GlueX experiment, the Central Drift Chamber (CDC) and the Forward Drift Chamber (FDC). The CDC is a cylindrical straw-tube detector covering polar angles between 6$^{\circ}$ and 168$^{\circ}$, delivering spatial resolution of $\sim$150 $\mu$m. The FDC is a Cathode Strip Chamber consisting of four packages, each with six alternating layers of anode wires and cathode strips. The FDC is designed to track forward-going charged particles with polar angles between 1$^{\circ}$ and 20$^{\circ}$ with a spatial resolution of $\sim$200 $\mu$m. Both tracking detectors record timing information and energy loss measurements useful for particle identification. During Fall 2014 and Spring 2015, the first photon beam was delivered on target for commissioning of the GlueX detector in Hall-D at Jefferson Lab. These data are currently being used in a large effort to calibrate the individual detector subsystems to achieve design performance. Methods and results for calibrations of each of the tracking detectors are presented. Techniques for alignment of the tracking system using a combination of cosmic rays and beam data is discussed. Finally, some early results of physics measurements including charged final-state particles are presented. [Preview Abstract] |
Friday, October 30, 2015 11:42AM - 11:54AM |
JF.00007: Gain Calibration of the Barrel Calorimeter in the GlueX Experiment William McGinley The GlueX experiment was built to produce and observe the spectrum of exotic hybrid meson states using a 9 GeV linearly polarized photon beam incident on a proton target. In order to achieve this goal GlueX uses electromagnetic calorimeters to detect neutral particles. There are two calorimeters, a barrel electromagnetic calorimeter and a forward electromagnetic calorimeter that offer a polar angular coverage from $11^{\circ}$ to $126^{\circ}$ and $2^{\circ}$ to $11^{\circ}$, respectively. Gain calibration of the calorimeters is important to improve the reconstructed energy resolution of neutral particles and allows for better detection of physics signals. To do the calibration we reconstruct a sample of $\pi^0$ events by detecting their decay photons in the calorimeters and minimize the width of the $\pi^0$ sample by adjusting the gains on each of the readout channels. The energy resolution for both calorimeters improved significantly as a result, and the gain calibration allowed preliminary studies of several physics channels from beam-commissioning data. The calorimeters calibration techniques and early physics results are presented and discussed. [Preview Abstract] |
(Author Not Attending)
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JF.00008: Performance of the GlueX Barrel Calorimeter Elton Smith, Mark Dalton, William McGinley, Zisis Papandreou The GlueX experiment at Jefferson Lab will search for exotic hybrid mesons, a new form of hadronic matter that exhibits gluonic degrees of freedom. We have taken data to commission the experiment and report here on the construction and performance of the electromagnetic barrel calorimeter (BCAL). The BCAL is a ``spaghetti calorimeter,'' consisting of layers of corrugated lead sheets, interleaved with planes of 1-mm-diameter, double-clad, scintillating fibers, bonded in the lead grooves using optical epoxy. This detector consists of 48 modules that are readout using 3,840 large-area Multi-Photon Pixel counter (MPPC) arrays [1]. The measured width of the $\pi^0$ mass peak is approximately 10 MeV, only slightly higher than projections based on prototypes [2]. Systematic studies are underway to understand the contributions to the resolution and improve its performance.\\[4pt] [1] O. Soto {\em et al.,} NIM A732 (2013) 431.\\[0pt] [2] B.D. Leverington {\em et al.,} NIM A596 (2008) 327. [Preview Abstract] |
Friday, October 30, 2015 12:06PM - 12:18PM |
JF.00009: A first look at reconstructed data from the GlueX detector Simon Taylor Construction of the GlueX detector in Hall D at the Thomas Jefferson National Accelerator Facility has recently been completed as part of the 12 GeV Upgrade to the facility. The detector consists of a barrel region containing devices for tracking charged particles and a lead-scintillator calorimeter for detecting photons, and a forward region consisting of two layers of scintillator paddles for time-of-flight measurements and a lead-glass electromagnetic calorimeter. The electron beam from the accelerator is converted into a photon beam by inserting a diamond radiator, thereby producing a coherent bremsstrahlung spectrum of photons impinging on a 30 cm-long LH2 target. The energy of the photon beam is determined using a tagging spectrometer. A commissioning run took place in Spring of 2015 during which all of the detector components were read out. Preliminary calibrations have been determined to a level sufficient to allow reconstruction of final states with several charged tracks and neutral particles. A first look at results of reconstruction of events using the GlueX detector will be presented. [Preview Abstract] |
Friday, October 30, 2015 12:18PM - 12:30PM |
JF.00010: ABSTRACT WITHDRAWN |
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