Session T10: Nuclear Instrumentation

Hypernuclei production experiment E01-011 at Jefferson Laboratory Hall C by (e, e'K$^{+}$) reaction

The experiment E01-011 was performed at JLab Hall C in 2005 to investigate high precision $\Lambda$ hypernuclei spectroscopy.The experimental setup consists of splitter magnet, Kaon spectrometer and electron spectrometer with elements compacted closely together to maximum the production yield. The electric current of splitter magnet was over loaded for tuning the beam in the experiment. This led to the saturation of the splitter magnetic field and cross talk of the leakage field among spectrometer element, which deformed the magnetic optics of spectrometer. Previous analysis started with an initial optics slightly modified from the designed one, and relied on the mathematic method tune to compensate the residual. Since only masses of $\Lambda$ and $\Sigma$ hyperons were reliable for the mathematic method optics tune, this may introduce extra uncertainties. A new optics was introduced based on the designed magnetic map by shift the geometric position and introduce asymmetric functions. The over all agreement of sieve slit hit pattern,independence of $\Lambda$ mass on kinematics were achieved by use the optics even without any mathematic method optics tune. The $\Lambda$ event counts for CH$_2$ target data was obtained $10\%$ more comparison with the previous analysis.   

Spin Light Polarimeter at 12 GeV

We plan to develop a realistic design for a novel polarimeter which will go a long way in satisfying the requirements of the precision experiments planned for the 12GeV era at Jefferson National Accelerator Facility (JLAB). A polarimeter based on the asymmetry in the spacial distribution of the spin light component of synchrotron radiation will make for a fine addition to the existing M\"oller and Compton polarimeters. The spin light polarimeter consists of a set of wriggler magnet along the beam that generate synchrotron radiation. The spacial distribution of synchrotron radiation will be measured by an ionization chamber after being collimated. As a part of the design process, simulation of the effects of fringe field of the 3-pole wriggler magnet that forms the primary component of the polarimeter is underway. The fringe field was simulated using LANL Poisson Superfish mesh EM solver. The results from the simulation, the preliminary design parameters of the polarimeter and its impact will be discussed.   

Mass Resolution in the Search for a New Boson in the APEX Experiment

The APEX experiment at Jefferson Lab is searching for a new vector boson A' with weak coupling to electrons in the mass range 65 MeV $< m_{A'} <$ 550 MeV. In this search for the A', establishing the mass resolution is critically important for determining the sensitivity of the experiment. The High Resolution Spectrometers (HRS) used in the APEX experiment have an excellent relative momentum resolution. The mass resolution is therefore dominated by the angular resolution. The angular resolution is dominated by three contributions: scattering of the $e^{+}e^{-}$ inside the target, track measurement errors by the HRS detectors, and imperfections in the magnetic optics reconstruction matrix. APEX held a three-week test run in July 2010, for which an A' search was performed in the mass range 175-250 MeV. We determined the final mass resolution of the test run to be between 0.85 and 1.11 MeV, depending on the invariant mass. This report will present a detailed account of the analysis procedure used to determine the final mass resolution.   

VHMPID: A Proposed New Detector for the ALICE Experiment

CERN (European Center for Nuclear Research) is a global laboratory that studies proton and heavy ion collisions at the Large Hadron Collider (LHC). ALICE (A Large Ion Collider Experiment) is one of four large experiments being of the LHC. ALICE is dedicated to the study of proton-proton collisions and the transition of matter to Quark Gluon Plasma in heavy ion collisions. The Very High Momentum Particle Identification Detector (VHMPID) is a proposed upgrade to the ALICE experiment. This detector performs charged hadron identification on a track-by-track basis in the 10 GeV/c $<$ p $<$ 25 GeV/c momentum range and provides ALICE with new opportunities to study parton-medium interactions at LHC energies. This capability will be unique to all LHC experiments and it builds on the existing particle identification in the lower momentum range. In this talk, we will describe the detector, some results from beam tests performed at CERN in June of last year, the physics possibilities that this detector will bring to the ALICE experiment, and the status of the project.   

The Assembly of the Forward Vertex Silicon Detector at Brookhaven National Laboratory

The Forward Vertex Silicon Vertex Detector (FVTX) is an upgrade to the PHENIX detector that was installed in December 2011 for its commissioning run and first data-taking in 2012. It is the muon arm counterpart of the VTX upgrade that was installed the previous year. This strip silicon detector is based on many highly integrated p-n junctions that provide precise position measurements. These measurements will help separate prompt particles from the initial collision from decay particles. The FVTX contains four cages (NW, SW, NE and SE,) each cage holds 4 disks of 48 silicon wedges. This detector will work in tandem with the muon arms of PHENIX, covering the pseudo-rapidity range of eta between 1.2 and 2.4. Construction and testing of the detector components, a multi-institution, international coordination, will be discussed. Current status of this detector's initial run will be provided.   

A New Muon Trigger for W-Physics at Forward Rapidity in PHENIX

The last decades have witnessed an enormous effort to understand nucleon spin structure. Nevertheless, many open questions remain. One important unresolved problem is the flavor dependence of quark and anti-quarks contributions to the nucleon spin. Parity violating W boson production in polarized proton-proton collisions at the Relativistic Heavy Ion Collider (RHIC) is sensitive to the flavor-dependence of quark and anti-quark spin contributions. Events including a W boson can be identified in the PHENIX experiment at RHIC by the presence of a high energy muon at forward rapidity. In order to improve the efficiency in selecting such events, the PHENIX collaboration has recently upgraded the muon trigger system of the two PHENIX forward muon spectrometers. The trigger upgrade consists of new front-end electronics for the muon tracking chambers, the installation of two new Resistive Plate Chamber (RPC) stations in each muon arm and new fast FPGA based trigger processor boards. The upgrade makes it possible to identify high momentum muons from W-decay within the 4 micro second latency of the PHENIX first level trigger. In this presentation, the upgrade design will be reviewed and the inital performance of the new muon trigger systems will be discussed.   

The PHENIX MuTrig Local Level One Trigger Upgrade at PHENIX

The PHENIX detector at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory has had robust forward muon tracking and identification from the MuTracker and MuID detector systems for many years. The addition of the resistive plate chamber (RPC) detectors in the forward region, as well as the upgrade of the muon tracker (MuTr) front-end electronics, allows for greater rejection of both collision related and non-collision related backgrounds at the trigger level. The MuTrig Local Level One (LL1) trigger system allows for the rejection of events without high momentum muons originating from the collision; this allows for collision event selection (such has W boson production). The LL1 trigger system was first operated during 2011 data taking, using half of the RPC detector system. For the ongoing 2012 data taking the RPC detector has~been expanded, increasing the capabilities of the LL1 trigger system's event selection. The operation~and~performance~of this expanded trigger system will be presented.   

Novel Zooming Scale Hough Transform Pattern Recognition Algorithm for the PHENIX Detector

Single ultra-relativistic heavy ion collisions at RHIC and the LHC and multiple overlapping proton-proton collisions at the LHC present challenges to pattern recognition algorithms for tracking in these high multiplicity environments. One must satisfy many constraints including high track finding efficiency, ghost track rejection, and CPU time and memory constraints. A novel algorithm based on a zooming scale Hough Transform is now available in Ref [1] that is optimized for efficient high speed caching and flexible in terms of its implementation. In this presentation, we detail the application of this algorithm to the PHENIX Experiment silicon vertex tracker (VTX) and show initial results from Au+Au at $\sqrt{s_{NN}}$ = 200 GeV collision data taken in 2011. We demonstrate the current algorithmic performance and also show first results for the proposed sPHENIX detector. \\[4pt] Ref [1] Dr. Dion, Alan. ``Helix Hough'' http://code.google.com/p/helixhough/   

A GEANT Model of the GEM-based Tracking Monitor for the STAR Experiment

In 2012, the STAR experiment at Brookhaven National Laboratory's Relativisitc Heavy Ion Collider (RHIC) plans to install a gaseous electron multiplier (GEM) based set of detector modules to provide high-precision tracking points for charged particles outside the volume of its primary detector, the time projection chamber (TPC). These modules will help in diagnosing and correcting for a number of tracking distortions in the TPC that arise in the high luminosity environment at RHIC. High statistics simulations of the performance of these modules are crucial to understanding their capabilities in diagnosing TPC calibration issues and require a detailed model of the detector modules integrated with the existing GEANT model of all STAR subsystems. We present current progress and results related to development and use of this model.   

Prototype of a Muon Tomography Station with GEM detectors for Detection of Shielded Nuclear Contraband

Muon tomography for homeland security aims at detecting well-shielded nuclear contraband in cargo and imaging it in 3D. The technique exploits multiple scattering of atmospheric cosmic ray muons, which is stronger in dense, high-Z materials, e.g. enriched uranium, than in low-Z and medium-Z shielding materials. We have constructed and are operating a compact Muon Tomography Station (MTS) that tracks muons with eight 30 cm $\times $ 30 cm Triple Gas Electron Multiplier (GEM) detectors placed on the sides of a cubic-foot imaging volume. A point-of-closest-approach algorithm applied to reconstructed incident and exiting tracks is used to create a tomographic reconstruction of the material within the active volume. We discuss the performance of this MTS prototype including characterization and commissioning of the GEM detectors and the data acquisition systems. We also present experimental tomographic images of small high-Z objects including depleted uranium with and without shielding and discuss the performance of material discrimination using this method.