120639175
Study of N* properties at CLAS
The excitation spectrum of the nucleon provides a stringent constraint on the dynamics and interactions of its internal constituents and therefore probes the mechanism of confinement in the light quark sector. Our detailed knowlege of this excitation spectrum is poor, with many predicted states not yet observed in experiment and many "established" states having poorly known properties. To address these shortcomings a worldwide effort is currently underway exploiting the latest generation of electron and photon beams in detailed studies of meson photoproduction from nucleon targets. A major contribution to this effort will come from the experimental programme at Jefferson Lab exploiting the frozen spin target (FROST) with the CLAS spectrometer. The status of this project will be presented along with preliminary results and analyses.
119383062
Three-nucleon mechanisms in photoreactions
Abstract The 12 C( γ ,ppn) reaction has been measured for E γ =150–800 MeV in the first study of this reaction in a target heavier than 3 He. The experimental data are compared to a microscopic many body calculation. The model, which predicts that the largest contribution to the reaction arises from final state interactions following an initial pion production process, overestimates the measured cross sections and there are strong indications that the overestimate arises in this two-step process. The selection of suitable kinematic conditions strongly suppresses this two-step contribution leaving cross sections in which up to half the yield is predicted to arise from the absorption of the photon on three interacting nucleons and which agree with the model. The results indicate ( γ ,3N) measurements on nuclei may be a valuable tool for obtaining information on the nuclear three-body interaction.
96911852
THE CRYSTAL BALL AT MAMI
55813045
The DIRC detectors of the PANDA experiment at FAIR
Abstract The P¯ANDA experiment at the planned FAIR facility at GSI, Darmstadt aims at measuring hadronic final states with unprecedented precision and luminosity. Superior particle identification of charged and neutral particles is mandatory to fulfil P¯ANDA's physics aims. DIRC (detection of internally reflected Cherenkov light) counters are foreseen for charged particle identification. A barrel DIRC will cover the central region while a disc DIRC will provide particle identification in the forward region. Three DIRC concepts differing in the radiator geometry and method for dispersion correction are studied. Results are presented on the common issues of radiator material and quality. Photon detection will be discussed as well.
119630665
Fast readout of GEM detectors for medical imaging
Abstract We describe the design and implementation of a fast data acquisition (DAQ) system for Gas Electron Multiplier (GEM) trackers applied to imaging and dosimetry in hadrontherapy. Within the AQUA project of the TERA foundation a prototype of Proton Range Radiography of 30×30 cm 2 active area has been designed and built to provide in-beam integrated density images of the patient before treatment. It makes use of a pair of GEMs to record position and direction of protons emerging from the target. A fast data acquisition rate close to 1 MHz will allow obtaining a good resolution in-beam proton radiography in a few seconds. A dedicated fast front-end circuit for GEM detectors (GEMROC by AGH-Crakow University) is read by the FPGA based DAQ card (GR_DAQ), developed by the AQUA group. The same system is under evaluation (within the ENVISION European project) to realize the in-vivo dosimetry, based on detecting secondary light particles during the treatment of the patient.
120740000
FGLD: a novel and compact micro-pattern gas detector
Abstract A new gas detector which combines in the same structure the gas amplification mechanism and the position sensitive readout, named the field gradient lattice detector (FGLD), is being developed at CERN. The detector, reminiscent in geometry of a multi-wire proportional chamber but with a different field configuration can be fabricated as two or more layers of micro-patterned parallel tracks on a variety of substrate materials. Two preliminary proof-of-concept designs without position sensitivity have been fabricated as copper tracks of 50 μ m width and 150 μ m pitch on polyimide in a 3D geometry and on epoxy in a 2D geometry. They have been shown to detect the 5.9 keV X-rays of an 55 Fe source with a stable gain ranging from 500 to 5000 in a 3 mm drift chamber containing an argon carbon-dioxide gas mixture. The elegance and compactness of the FGLD design make it a very attractive gas detector solution both economically and mechanically. Most interestingly, the 3D FGLD design on flexible polyimide should greatly simplify the mechanical challenges of gas chamber assembly in planar and cylindrical detector designs.