[en] In late 1992 and early 1993, the DLS collaboration performed measurements in several A+A systems at a beam kinetic energy of 1.05 GeV/nucleon. Although the analysis of the data sets from Ca+Ca, He+Ca, C+C, and d+Ca systems are still preliminary, a brief discussion of this experimental program as well as the pair statistics from these measurements will be given in this report

[en] An analytic model, derived from coupled continuity equations for the electron and neutral deuterium densities, is consistent with many features of edge electron density profiles in the DIII-D tokamak. For an assumed constant particle diffusion coefficient, the model shows that particle transport and neutral fueling produce electron and neutral density profiles that have the same characteristic scale lengths at the plasma edge. For systematic variations of density in H-mode discharges, the model predicts that the width of the electron density transport barrier decreases and the maximum gradient increases, as observed in the experiments. The widths computed from the model agree quantitatively with the experimental widths for conditions in which the model is valid. These results support models of transport barrier formation in which the H-mode particle barrier is driven by the edge particle flux and the width of the barrier is approximately the neutral penetration length

[en] Measured dielectron cross sections from Ca+Ca, C+C, He+Ca, and d+Ca reactions at 1.0 A.GeV are presented. The invariant mass spectrum from Ca+Ca collisions is discussed and compared with results from model calculations. The four A-A measurements are used to explore the physics content of the e⁺e^- signal that is not explained by the models. (orig.)

[en] We present preliminary two-particle correlations for unidentified hadrons in p-p collisions at √s =200 GeV. On two-particle transverse rapidity space y_t x y_t two distinct regions of correlated pairs are observed: a peaked structure at low y_t (p_t ≤ 0.4 GeV/c) and a broad structure at higher y_t, where the correlation is distributed as a 2D Gaussian centered at y_t1 = y_t2 ≅ 2.8 (p_t1, p_t2 ≅ 1.2 GeV/c). We select those regions separately, projecting correlations onto momentum-difference variables (η_Δ, φ_Δ), and observe structures interpretable in the context of string and parton fragmentations from soft and semi-hard components of p-p collision. (author)

[en] The authors used ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) to study nine patients with clinical absence or generalized seizures. One patient had only absence seizures, two had only generalized tonic-clonic seizures, and six had both seizure types. Interictal scans in eight failed to reveal focal or lateralized hypometabolism. No apparent abnormalities were noted. Two patients had PET scans after isotope injection during hyperventilation-induced generalized spike-wave discharges. Diffusely increased metabolic rates were found in one compared with an interictal scan, and in another compared with control values. Another patient had FDG injected during absence status: EEG showed generalized spike-wave discharges (during which she was unresponsive) intermixed with slow activity accompanied by confusion. Metabolic rates were decreased, compared with the interictal scan, throughout both cortical and subcortical structures. Interictal PET did not detect specific anatomic regions responsible for absence seizure onset in any patient, but the results of the ictal scans did suggest that pathophysiologic differences exist between absence status and single absence attacks

[en] Measurements of dielectron production in heavy-ion collisions are valuable probes into the dynamics of the collision process. While the hadronic participants of the collision are subject to strong final state interactions, the coupling of the electron-positron pair to the collision medium is electromagnetic. Dielectrons, therefore suffer little rescattering leaving the interaction and can retain information about their production origins, probing even the early stages in the evolution of the collision. The DiLepton Spectrometer (DLS) collaboration's original measurements of dielectron production established the existence of the signal at Bevalac energies. The 1992- 93 DLS measurements in nucleus+Nucleus collisions at a kinetic beam energy of 1.05 GeV/nucleon are the subject of this presentation

[en] The authors present experimental results on the pd/pp ratio for e⁺e^-production and the invariant e⁺e^- mass distribution measured in the process p+p→e⁺e^-+X at energies between 1.03 and 4.9 GeV. From the mass spectra production cross sections for η, ρ, ω, and Δare derived. (HSI)

[en] Measurements of dielectron production in p+p and p+d collisions with beam kinetic energies from 1.04 to 4.88 GeV are presented. The differential cross section is presented as a function of invariant pair mass, transverse momentum, and rapidity. The shapes of the mass spectra and their evolution with beam energy provide information about the relative importance of the various dielectron production mechanisms in this energy regime. The p+d to p+p ratio of the dielectron yield is also presented as a function of invariant pair mass, transverse momentum, and rapidity. The shapes of the transverse momentum and rapidity spectra from the p+d and p+p systems are found to be similar to one another for each of the beam energies studied. The beam energy dependence of the integrated cross sections is also presented. copyright 1998 The American Physical Society

[en] Dielectron production in p+d and p+p collisions at the beam kinetic energy of 4.9 GeV has been measured with the Dilepton Spectrometer. Features of the dielectron cross section have been studied with cuts on the mass and transverse momentum of the pairs. The spectra for several regions of phase space are presented as a function of the pair mass and transverse momentum

[en] We present measured dielectron production cross sections for Ca+Ca, C+C, He+Ca, and d+Ca reactions at 1.0 A GeV . Statistical uncertainties and systematic effects are smaller than in previous dilepton spectrometer (DLS) nucleus-nucleus data. For pair mass M≤0.35 GeV/c² we obtain (1) the Ca+Ca cross section is larger than the previous DLS measurement and current model results, (2) the mass spectra suggest large contributions from π⁰ and η Dalitz decays, and (3) dσ/dM∝A_PA_T. For M>0.5 GeV/c² the Ca+Ca to C+C cross section ratio is significantly larger than the ratio of A_PA_T values. copyright 1997 The American Physical Society