[en] An extensive program dedicated to the study of open strangeness systems was established in Hall B at Jefferson Lab. This program takes full advantage of the excellent characteristics of the CEBAF accelerator combined with the almost complete angular coverage of the CLAS detector. A general overview of the program is given, as well as results for the angular dependence of the electroproduction of kaon-hyperon final states

[en] The authors review the status of inclusive electron-proton scattering F₂ structure function data in both the nucleon resonance region and the deep inelastic region, at momentum transfers below 5 (GeV/c)². From these data they construct moments of F₂, down to momentum transfers of Q²∼0.1(GeV/c)². The second moment is only slowly varying with Q² down to Q²∼1, which is a reflection of duality. Below Q² of 1 (GeV/c)², the Q² dependence of the moments is predominantly governed by the elastic contribution, whereas the inelastic channels still seem governed by local duality

[en] We investigate the Q² dependence of inclusive electron-proton scattering F₂ structure function data in both the nucleon resonance region and the deep inelastic region, at momentum transfers below 5 (GeV/c)². From these data we construct moments of F₂, down to momentum transfers of Q²∼0.1 (GeV/c)². The second moment is only slowly varying with Q² down to Q²∼1 (GeV/c)², which is a reflection of duality. Below Q² of 1 (GeV/c)², the Q² dependence of the moments is predominantly governed by the elastic contribution, whereas the inelastic channels still seem governed by local duality

[en] We present measurements of the differential cross section and Lambda recoil polarization for the gamma p to K+ Lambda reaction made using the CLAS detector at Jefferson Lab. These measurements cover the center-of-mass energy range from 1.62 to 2.84 GeV and a wide range of center-of-mass K+ production angles. Independent analyses were performed using the K+ p pi- and K+ p (missing pi -) final-state topologies; results from these analyses were found to exhibit good agreement. These differential cross section measurements show excellent agreement with previous CLAS and LEPS results and offer increased precision and a 300 MeV increase in energy coverage. The recoil polarization data agree well with previous results and offer a large increase in precision and a 500 MeV extension in energy range. The increased center-of-mass energy range that these data represent will allow for independent study of non-resonant K+ Lambda photoproduction mechanisms at all production angles.

[en] The result of a feasibility study to measure the Lambda polarization in associated K+ -Lambda electro production is presented. This measurement was performed in the experimental Hall C at Jefferson Lab. The scattered electron was detected in the HMS spectrometer, and the electro-produced kaon and the proton from the Lambda -> ppi- decay were both detected in the SOS spectrometer. This quantity is very sensitive to the elementary p(e,e'K) [capital Lambda, Greek] process and gives information on resonance production, and Regge exchange, among others. The result presented was measured at Q2=1.50 (GeV/c)2 and cos [straight theta, small theta, Greek] K [small gamma, Greek] CM=14^o. The limits of the [capital Lambda, Greek] polarization, with respect to the p [small gamma, Greek] x pK axis, were found to be -0.21 and +0.89 with a confidence level of 68%. The result is compared to theoretical predictions based on an effective hadronic field Lagrangian model and a Regge framework model

[en] In the early '90 we developed a laboratory technology for HTS Zimmerman SQUIDs manufacturing. It includes tools, working procedures, instruments for testing and measuring of the resulting devices. Taking an YBCO pellet as a promising material, a systematic activity to improve it followed. The effects of pressure, annealing temperature and annealing time on SQUID characteristics like signal to noise ratio and manufacturing yield were studied. So, we determined the corresponding technological parameters and prepared a good superconducting material for SQUID manufacturing. In the process, tests revealed anomalous SQUIDs. These exhibit a triangle like flux-voltage characteristics but any two adjacent triangles have different heights. When making the weak link thinner, some anomalous SQUIDs become normal. The first ones present a practical interest because their response signal to flux deviations is higher than that of the usual SQUIDs. We developed flux meters having superconducting transducer. Their noise limited resolution was rather poor: 0.1 Φ₀ when integrator time constant equals 10 ms (Φ₀ = 2.05 x 10^-15 Wb is the flux quantum). This value is due to both the noises of the electronics and to the magnetic environment. We succeeded to improve the electronics up to the level where its input noise equivalent voltage equals the noise voltage generated by the resonant circuit coupled to the SQUID. That's why we account the result as an end point on this way. Superconducting shields are very effective: the attenuation factor of the magnetic induction B external axial component is larger than 600, in the symmetry center, when the length to inner diameter ratio of a cylindrical shell equals 3. When the external magnetic induction supersedes the critical value (B_c = 12 mT) and the external field has a harmonic component too, the inner harmonic component is opposite in phase. This is an unexpected result. The work is in progress. (authors)

[en] Photomultiplier tubes continue to be a reliable, cost-effective means of detecting light produced by the interaction of subatomic particles with detectors. For detectors where the expected light yield is modest, characterizing the low light response of the tube is of paramount importance. Several phenomenological models addressing this issue exist. This paper presents side-by-side comparison between three such approaches as they arose from a large scale testing of tubes to be used by a Ring Imaging Cherenkov detector at Jefferson Lab. The main characteristics of the tubes, such as the gain, were found to be consistent within the expected uncertainties for all models considered. Leveraging the extensive nature of the study, a machine learning algorithm based on an artificial neural network capable of obtaining the tube characteristics directly from the raw ADC data was developed and trained. The trained neural network produced results fully compatible with the three models considered, with substantial savings in both computation time and experimenter overhead.

[en] Electroproduction of strange particles is studied at the Thomas Jefferson Continuous Beam Electron Accelerator for polarised and unpolarized electron beam on a hydrogen unpolarized target. Exclusive e + p → e' + K⁺ + Λ/Σ⁰ for energies between 2.445 GeV and 4.045 GeV give information about longitudinal and transverse differential cross sections, and induced and transferred polarisation to the hyperon. Preliminary results are shown in order to demonstrate the experimental possibilities in obtaining model independent results which can test vector dominance and quark models. The E93-018 experiment at TJNAF leads to results which can provide new information on hadron structure in a boundary region between intermediate and high energy physics

[en] The paper presents some experimental results concerning fabrication through powder metallurgy (P/M) of aluminum-based hybrid composites - Al/Al₂O₃/Gr. In order to understand the mechanisms that occur during the P/M processes of obtaining Al/Al₂O₃/Gr composite, we correlated the physical characteristics with their micro-structural characteristics. The characterization was performed using analysis techniques specific for P/M process, SEM-EDS and XRD analyses. Micro-structural characterization of the composites has revealed fairly uniform distribution this resulting in good properties of the final composite material. (paper)

[en] Inclusive electron scattering data are presented for ²H and Fe targets at an incident electron energy of 4.045 GeV for a range of momentum transfers from Q² = 1 to 7 (GeV/c)². Data were taken at Jefferson Laboratory for low values of energy loss, corresponding to values of Bjorken x greater than or near 1. The structure functions do not show scaling in x in this range, where inelastic scattering is not expected to dominate the cross section. The data do show scaling, however, in the Nachtmann variable ξ. This scaling may be the result of Bloom Gilman duality in the nucleon structure function combined with the Fermi motion of the nucleons in the nucleus. The resulting extension of scaling to larger values of ξ opens up the possibility of accessing nuclear structure functions in the high-x region at lower values of Q² than previously believed