[en] The GlueX detector facility in Hall-D at Jefferson lab in Newport News is part of the 12 GeV upgrade and dedicated to the search for gluonic degrees of freedom in mesons by scattering high energy linearly polarized real photons of up to 9 GeV from nucleon targets. Civil construction of the Hall-D complex has started as well as the construction of the various detector components. The current status of the project is outlined here.

[en] Over the course of more than a decade the HERMES experiment has accumulated a wealth of data with electron and positron beams on various gaseous targets from Hydrogen up to Xenon. In addition, the beams and targets can be polarized. This data set is viewed in the context of Generalized Parton Distributions, a theoretical formalism with an explicit three dimensional view of the structure of the nucleon. It provides a link between experimental observables and the total angular momentum of the quarks in the nucleon.

[en] While gluonic degrees of freedom in nucleons are well established its counter part in mesons has not been confirmed. The properties of the of mesons are attributed to quark degrees of freedom only. The GlueX detector facility in Hall-D at Jefferson lab in Newport News is part of the 12 GeV upgrade and dedicated to the search for gluonic degrees of freedom in mesons by scattering high energy linearly polarized real photons of up to 9 GeV from nucleon targets. To provide the necessary good detection coverage over 4 π, part of the detector resides within a large solenoid magnet surrounding the target. In the bore of the magnet a straw tube cylindrical drift chamber around the target and a series of cathode-strip wire chambers downstream of the target are used for particle tracking. Two electromagnetic calorimeters, one cylindrical shaped inside the magnet (BCAL) and one downstream (FCAL) of the magnet provide the necessary detection capabilities of photons from neutral meson decays. The former is based on a lead scintillation fiber matrix the latter on lead glass. The optical readout of the BCAL is based on silicon photo multipliers that are insensitive to the high magnetic field of the solenoid. A cylindrical plastic scintillator hodoscope around the target and two hodoscope planes downstream of the solenoid in front of the FCAL electromagnetic calorimeter complement the detector by providing timing information. To handle the large data rate, custom electronics for digitization, trigger and readout has been developed and built at Jefferson Lab. The flash analog to digital converters run at 250 MHz sampling the analog signal every 4 ns and forming energy sums at the same rate. This information is shipped via optical link at the same 250 MHz rate to a trigger decision logic. Data readout rates of up to 300 MB/s are expected to be written to disk at high luminosity running. The level 1 trigger electronics uses VXS, a VME based system with a high-speed switch-fabric on the back plane. Detector construction is starting now and the facility is expected to start operation in April 2014. (author)

[en] The search for gluonic degrees of freedom in mesons is an experimental challenge. The most promising approach is to look for mesons with exotic quantum numbers that can not be described by quark degrees of freedom only. The GlueX experiment at Jefferson Lab in Hall-D, currently under construction, will search for such hybrid mesons with exotic quantum numbers by scattering a linearly polarized high energetic photon beam off a liquid hydrogen target. An amplitude analysis will be employed to search for such resonances in the data and determine their quantum numbers.

[en] We measured the 0 deg. polarization transfer of the ²H(p→, n→)pp reaction used to produce a high-intensity, monoenergetic neutron beam. The 0⁺ → 0⁺ reaction ¹⁴C(p→, n→) ¹⁴N(2.31) has been used to calibrate a high-efficiency polarimeter, which in turn was used to measure the polarization transfer in ²H(p→, n→)pp. With this data the uncertainty on the polarization of the 70 MeV neutron beam, used for many different studies at PSI, is reduced to 1.1%. The data are compared to predictions of Faddeev calculations based on realistic nucleon-nucleon interactions

[en] We have measured the tensor analyzing power of d-⁴He elastic scattering at θ_d=150 in the energy range from 30 to 52 MeV. In this region the analyzing power is large, and the process can be employed as a standard to calibrate the tensor polarization of deuteron beams. (orig.)

[en] Polarized beam commissioning has been initiated at TJNAF. Measuring the polarization properties of the accelerator, which consists of two superconducting linacs and more than 2200 magnetic elements at its maximum energy, provide useful information about the beam energy and beam transport through the accelerator. Stability of the output beam polarization depends upon time-dependent orbit and energy oscillations. Modeling indicates that the spin transport dynamics are sensitive (∼10^-2) to vertical betatron oscillations in the recirculation arcs. This sensitivity is calculated to be enhanced in the arcs where the spin tune is most nearly matched to the vertical betatron tune. Modeling also suggests that depolarization phenomena associated with the particle trajectory differences for electrons within the accelerator's nominal transverse phase volume are too small to be measured between the injector and an experimental hall. Preliminary results from measurements obtained during polarization development runs will be presented. copyright 1998 American Institute of Physics

[en] We have built a polarimeter in order to measure the electron beam polarization in hall C at JLAB. Using a superconducting solenoid to drive the pure-iron target foil into saturation, and a symmetrical setup to detect the Moeller electrons in coincidence, we achieve an accuracy of <1%. This sets a new standard for Moeller polarimeters

[en] We have built a polarized proton and deuteron target for experiments using intense high-energy electron beams. This system exploits dynamical nuclear polarization of irradiated ammonia in a 5 T magnetic field at temperatures near 1 K. We describe the various features and the performance of the target

[en] Polarized beam commissioning has been initiated at TJNAF. Measuring the polarization properties of the accelerator, which consists of two superconducting linacs and more than 2200 magnetic elements at its maximum energy, provide useful information about the beam energy and beam transport through the accelerator. Stability of the output beam polarization depends upon time-dependent orbit and energy oscillations. Modeling indicates that the spin transport dynamics are sensitive (∼10^-2) to vertical betatron oscillations in the recirculation arcs. This sensitivity is calculated to be enhanced in the arcs where the spin tune is most nearly matched to the vertical betatron tune. Modeling also suggests that depolarization phenomena associated with the particle trajectory differences for electrons within the accelerator's nominal transverse phase volume are too small to be measured between the injector and an experimental hall. Preliminary results from measurements obtained during polarization development runs will be presented