Experimental study of exclusive 2H(e,e'p)n reaction mechanisms at high Q2

The reaction 2H(e,e'p)n has been studied with full kinematic coverage for photon virtuality 1.75NN transition is the primary contribution at higher momenta.     

A self-driven laser oscillator for directly producing bandwidth-limited pulses of about 1 nsec

We report a self-driven Nd:YAG oscillator system that directly produces bandwidth-limited output pulses with durations from < 0.5 to #62; 2.5 nsec. We obtain the pulses by independently adjusting the temporal content of an initially gated noise pulse, the frequency dependent feedback properties of the optical cavity, and the system gain.     

Wrap-around partitioning for block bidiagonal linear systems

A stable vector algorithm for the solution of block diagonallinear systems is obtained by a permutation of the unknownscalled wrap-around partitioning combined with standard QR factorization.Wrap-around partitioning uses blocking and selects the unknownsin the blocks in turns. After a suitable orthogonal eliminationstep one ends up with a reduced system which is again blockbidiagonal and so wrap-around partitioning can be applied again.Using a simple model for vectorization overhead it is shownthat small block sizes give best performance. The minimal blocksize 2, which corresponds to cyclic reduction, is suboptimaldue to memory bank conflicts.     

Measurement of deeply virtual compton scattering beam-spin asymmetries

The beam-spin asymmetries in the hard exclusive electroproduction of photons on the proton (e p-->epgamma) were measured over a wide kinematic range and with high statistical accuracy. These asymmetries result from the interference of the Bethe-Heitler process and of deeply virtual Compton scattering. Over the whole kinematic range (x(B) from 0.11 to 0.58, Q2 from 1 to 4.8 GeV2, -t from 0.09 to 1.8 GeV2), the azimuthal dependence of the asymmetries is compatible with expectations from leading-twist dominance, A approximately a sinphi/(1+c cosphi). This extensive set of data can thus be used to constrain significantly the generalized parton distributions of the nucleon in the valence quark sector.     

Water-vapor adsorption on calcium-boroaluminosilicate glass fibers

The water-vapor adsorption isotherms of E-glass fibers were measured as a function of their aging in humid and aqueous environments, and of the amount of B₂O₃ in the glass composition. The specific surface area for adsorption was determined, independently, using inert gas adsorption, while X-ray photoelectron spectroscopy (XPS) was used to characterize the surface composition. In contrast to silica, where submonolayer coverage is observed in the low pressure range of the isotherm, these multicomponent glasses adsorbed the equivalent of 1 to 3 layers of water. The shape of the isotherms revealed that multilayer adsorption of water occurs on the fiber surfaces before the formation of a complete monolayer, i.e., water adsorption on these glass fibers was non-uniform, in general. It was found that the aging of these fibers in humid or aqueous environments greatly enhanced their capacity to adsorb water at low pressure, but the B₂O₃ content of the fibers had little effect.