Chargino Production and Decay in Photon-Photon-Collisions

We discuss the pair production of charginos in collisions of polarized photons $\gamma\gamma \to \tilde{\chi}_i^+ \tilde{\chi}_i^-$, ($i=1,2$) and the subsequent leptonic decay of the lighter chargino $\tilde{\chi}_1^+ \to \tilde{\chi}_1^0 e^+ \nu_e$ including the complete spin correlations. Analytical formulae are given for the polarization and the spin-spin correlations of the charginos. Since the production is a pure QED process the decay dynamics can be studied separately. For high energy photons from Compton backscattering of polarized laser pulses off polarized electron beams numerical results are presented for the cross section, the angular distribution and the forward-backward asymmetry of the decay positron. Finally we study the dependence on the gaugino mass parameter $M_1$ and on the sneutrino mass for a gaugino-like MSSM scenario.Comment: 22 pages, 15 figures, version to be published in Eur. Phys. J.

Determination of the Gaugino Mass Parameter M_1 in Different Linear Collider Modes

We study the different linear collider modes with regard to the determination of the gaugino mass parameter M_1. In a specific mSUGRA inspired scenario we compare four processes with polarized beams: (a) e+ e- --> neutralino_1 neutralino_2 --> neutralino_1 neutralino_1 e+ e-, (b) e- gamma --> neutralino_1 selectron_{L/R} --> neutralino_1 neutralino_1 e-, (c) gamma gamma --> chargino_1^+ chargino_1^- --> neutralino_1 neutralino_1 e+ e- neutrino_e anti-neutrino_e, (d) e- e- --> selectron_{L/R} selectron_{L/R} --> neutralino_1 neutralino_1 e- e-.Comment: 5 pages, 8 figures, LaTex, Talk given at the 5th International Linear Collider Workshop (LCWS 2000), Fermilab, Batavia, Illinois, Oct. 24-28, 200

On the spectrum of Farey and Gauss maps

In this paper we introduce Hilbert spaces of holomorphic functions given by generalized Borel and Laplace transforms which are left invariant by the transfer operators of the Farey map and its induced version, the Gauss map, respectively. By means of a suitable operator-valued power series we are able to study simultaneously the spectrum of both these operators along with the analytic properties of the associated dynamical zeta functions.Comment: 23 page

Absolute differential cross sections for electron-impact excitation of CO near threshold: II. The Rydberg states of CO

Absolute differential cross sections for electron-impact excitation of Rydberg states of CO have been measured from threshold to 3.7 eV above threshold and for scattering angles between 20° and 140°. Measured excitation functions for the b 3Σ+, B 1Σ+ and E 1π states are compared with cross sections calculated by the Schwinger multichannel method. The behaviour of the excitation functions for these states and for the j 3Σ+ and C 1Σ+ states is analysed in terms of negative-ion states. One of these resonances has not been previously reported

Variations of porosity in calcareous sediments from the Ontong Java Plateau

Based on index properties measurements made on board the JOIDES Resolution, we studied porosity changes with depth in the fairly homogeneous deep-sea calcareous sediments cored during Ocean Drilling Program Leg 130 on the Ontong Java Plateau. Using Leg 130 data, we present evidence that the rate of porosity decrease with burial in calcareous oozes and chalks is related to the depth of deposition and thus probably depends on the conditioning of calcareous sediments by winnowing or dissolution processes during the time of deposition. The ooze-to-chalk transition is not clearly reflected in porosity profiles. In the ooze-chalk sections studied (the upper 600 mbsf), mechanical compaction is most likely the major process controlling the porosity decrease with depth of burial, whereas the chalk-limestone transition (at about 1100 mbsf at Site 807) is characterized by an intense chemical compaction leading to a drastic decrease in porosity values within 100 m. In oozes and chalks, porosity values were corrected to original (uncompacted) values using site-specific empirical regression equations. When plotted vs. age, corrected porosity profiles appear to correlate quite well from site to site in the sediments deposited during the last 15 m.y. This observation has considerable implications for seismic stratigraphy. Our attempt to correlate variations in porosity (or wet-bulk density) profiles with changes in carbonate content remained unsatisfactory. Index properties changes are likely caused by changes in the foraminifer content. If this is the case, we propose that large-scale porosity fluctuations that correlate from site to site are the result of changes in the surface productivity that lead to changes in the foraminifers-to-nannofossils ratio

Analytical performance of the selective multianalyser Olympus AU 5200

The analytical performance of a selective, automatic multianalyser- the Olympus A U5200 - was tested and assessed for practicability, following ECCLSguidelines. Twenty-two analytes were tested and compared with the Olympus A U5000 analyser. A Hitachi 747 analyser was also included in this survey in order to obtain correlation data for ISE measurements

Gamma–ray spectroscopy with single–carrier collection in high–resistivity semiconductors

With the standard plane–parallel configuration of semiconductor detectors, good γ–ray spectra can only be obtained when both electrons and holes are completely collected. We show by calculations (and experiments) that with contacts of hemispherical configuration one can obtain γ–ray spectra of adequate resolution and with signal heights of nearly full amplitude even when only one type of carrier is collected. Experiments with CdTe detectors for which the µτ product for electrons is about 10^(3) times that of the holes confirm these calculations. The adoption of hemispherical contacts thus widens the range of high–resistivity semiconductors potentially acceptable for γ–ray detection at room temperature

Laboratory and Well-Log Velocity and Density Measurements from the Ontong Java Plateau: New in-situ corrections to laboratory data for pelagic carbonates

During Ocean Drilling Program Leg 130, sonic velocity and bulk density/porosity well logs were measured in five separate holes drilled through the sequence of pelagic carbonate oozes, chalks, and limestones that comprise the thick, continuous sedimentary cover on the Ontong Java Plateau. An internally consistent and continuous suite of shipboard laboratory velocity and sediment physical properties measurements were made from the top of each hole down through the entire logged interval. Because of the high quality of the data, extensive overlap of 500 m or more between the log and laboratory measurements at each hole, and the homogeneous nature of the sediments, we have been able to compare laboratory and in-situ log measurements in detail and to evaluate factors that alter laboratory data from their in-situ values. For measurements of bulk density and porosity, differences between laboratory and in-situ log measurements are very small and remain constant over the entire range of depths studied. We have applied a simple hydraulic rebound correction to the laboratory data that compensates for pore fluid expansion after removal of a sediment sample from in-situ conditions. The small, correctable differences between the laboratory and log data imply that mechanical rebound is significantly less than previous estimates (maximum near 5%) of rebound in pelagic carbonates. Furthermore, porosity rebound cannot be used to correct laboratory sonic velocity measurements to in-situ values. Such a rebound correction implicitly requires that laboratory and in-situ data must occupy identical fields on velocity-porosity crossplots. This condition is not met for the Ontong Java Plateau results because laboratory and in-situ logging data occupy distinct trends with little overlap between the two types of measurement. Mechanical rebound in pelagic carbonates cannot be used to correct either laboratory porosity or velocity measurements to in-situ values. The complex porosity systematics of these carbonates resulting from varying abundances of hollow foraminifer grains precluded use of an empirical correction derived from the log porosity and velocity data. Laboratory sonic velocity measurements can be corrected to in-situ values at all of the Ontong Java Plateau sites using a depth-based function derived from downhole differences between log and laboratory velocities in Hole 807A. The applicability of the depth correction implies that the effect of overburden pressure reduction on sediment elastic moduli is the most significant factor affecting laboratory velocity measurements. The depth correction to laboratory velocity measurements appears to be generally applicable to pelagic carbonate oozes and chalks of the Ontong Java Plateau, regardless of depositional depth or sediment age