A Large-Acceptance Forward Angle Spectrometer (Super BigBite) is under development for the upcoming experiments in Hall A at Jefferson Lab to optimally exploit the exciting opportunities offered by the 12 GeV upgrade of the electron beam. The tracking of this new apparatus is based on the Gas Electron Multiplier technology, which has been chosen to optimize cost/performance, position resolution and meet the high hits rate (>1 MHz/cm2). In this report we present the technical features of the detector and comment on the presently achieved performance.

We have studied the role of on-site electronic correlation on the band structure of Bi 2Sr 2CaCu 2O 8 . In our approach, an ab initio calculation supplies for the single particle starting point, on top of which self-energy effects are explicitly taken into account in the framework of the three-body scattering theory (3BS). We observe that correlation modifies the energy dispersion of hole quasiparticle states near the Fermi level, especially close to the X and M symmetry points, but does not induce sensible changes at the Fermi level. To sustain this picture, we report calculations of effective masses. [All rights reserved Elsevier]

We report the status of the Data Acquisition (DAQ) system for the Coordinate Detector (CDET) module of the Super Bigbite Spectrometer facility at Hall A of Thomas Jefferson Accelerator Facility. Presently, the DAQ is fully assembled and tested with one CDET module. The commissioning of CDET module, that is the goal of the tests presented here, consists essentially in the measures of the amplitude and time-over-threshold of signals from cosmic rays. Hardware checks, the developing of DAQ control and off-line analysis software are ongoing; the module currently seems to work roughly accordingly to expectations. Data presented in this note are still preliminary.

Review: 55 refs.

A plastic scintillating disc (NE102, 3 cm thick, 1 m diameter) has been designed for detecting charged pions in nuclear reactions at intermediate energy. A hole of 20 cm diameter was made in the middle of the disc in order to allow for the beam passage through the detector. The originality of the detector consists of the simultaneous use of four very compact central photomultiplier tubes (PMT) and eight peripheral PMTs in order to retrieve the hitting point of a charged particle onto the disc surface with a space resolution of plusmn3 cm. The original method has been developed by using polar coordinates and only the time-of-flight information (TOF) from three or four nearest PMTs, including at least one central PMT

We present detailed first-principles calculations of the normal state electronic properties of the Bi 2Sr 2CaCu 2O 8 (Bi-2212) high T C superconductor by means of the linearized augmented plane wave (LAPW) method within the framework of density functional theory (DFT). We describe the crystal structure by the body-centered tetragonal (BCT) cell with space group I4/mmm and optimize its volume, c/a ratio and atomic positions by total energy and atomic-force minimization. The optimization of the cell leads to small but visible changes in the topology of the Fermi surface, rounding the shape of the CuO 2 barrels, and moving both the BiO bands, responsible for the pockets near the M point, below the Fermi level. We have then studied the influence of the large distortions in the BiO plane observed in nature by means of an radic2timesradic2 orthorhombic cell (with Bbmb space group). Differently to what has been observed in the literature for the Bi-2201 compound, we find that for Bi-2212 the orthorhombic distortion does not induce relevant changes to the binding energies of the BiO bands, conserving their metallic character

The readout of a cheap scintillating fibre was implemented by means of a new solid-state device (Silicon Photomultiplier, SiPM), able to detect very tiny light pulses. The GEANT3.21 code was adopted to simulate the counting detection efficiency and the energy deposited inside the scintillating fibre due to the radiation of a radioactive gamma source. The results obtained show the capability to detect gamma rays producing as few as 3–4 photoelectrons. The new devices may have many applications in radioactivity metrology.

The readout of a cheap scintillating fibre was implemented by means of a new solid-state device (Silicon Photomultiplier, SiPM), able to detect very tiny light pulses. The GEANT3.21 code was adopted to simulate the counting detection efficiency and the energy deposited inside the scintillating fibre due to the radiation of a radioactive gamma source. The results obtained show the capability to detect gamma rays producing as few as 3–4 photoelectrons. The new devices may have many applications in radioactivity metrology.

An experimental investigation has been carried out on the properties of electromagnetic shower detectors, composed of a uniform array of plastic scintillating fibers and lead (50:35 by volume ratio) for photons in the energy range 600-1200 MeV. When the photon's incidence angle to the fiber axis is within plusmn2deg an energy resolution of sigma E/E(%)=5.12/radic(E[GeV])+1.71 has been observed

The photofission yields of Bi induced by the quasi-monochromatic photon beam from in-flight annihilation of positrons of the Frascati linac were measured. The experiment was performed at sixteen different positron energies, from 120 MeV up to 280 MeV, by collecting the annihilation photons at angles 0.5deg

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The authors discuss the advantages that can be attained in performing photofission experiments by using a linearly polarized photon beam. The features of the longitudinal and transversal fragment angular distributions in fission induced by polarized photons are shown. A procedure to extract information on the fission channels is worked out in details. An experimental arrangement for the measurements of the photofission angular distributions is finally suggested in connection with the main characteristics of a polarized monochromatic photon beam now available at the Frascati National Laboratories (Italy)

The dependence of the fission fragment kinetic energy on the compound-nucleus excitation energy has been studied to explain a number of questions still unanswered in fission theory. The authors use glass sandwiches, previously employed for fission cross-section measurements, to measure both the diameters of the two etched pits due to each event of binary fission. The aim of the experiment is to distinguish the light fragment from the heavy one and so to obtain the energy distribution of both the fission fragments, as the diameter of etched tracks on glass is related to the energy of the fragments. The measurements were performed on the fragments from 238U(n,f) reaction at neutron energies En=1.8 MeV, 5.2 MeV, 12.7 MeV, 14.5 MeV and 16.8 MeV