Four-fermion decay of Higgs bosons

We calculate four-fermion decays of a Higgs boson via $WW$ and/or $ZZ$ intermediate states for Higgs masses below $m_W$. We examine models with a doubly-charged Higgs boson $H^{++}$ and show that the four-fermion decay is the dominant mode for a wide range of parameter space. Existing searches for $H^{++}$ in $Z$ decays have not looked for this mode. We also derive four-fermion decay rate for a neutral Higgs boson.Comment: 12 pages, 4 figures, uses an obsolete version of phyzzx with modification (included in the file). Missing preprint no. adde

Radiation resistance and comparative performance of ITO/InP and n/p InP homojunction solar cells

The radiation resistance of ITO/InP cells processed by DC magnetron sputtering is compared to that of standard n/p InP and GaAs homojunction cells. After 20 MeV proton irradiations, it is found that the radiation resistance of the present ITO/InP cell is comparable to that of the n/p homojunction InP cell and that both InP cell types have radiation resistance significantly greater than GaAs. The relatively lower radiation resistance, observed at higher fluence, for the InP cell with the deepest junction depth, is attributed to losses in the cells emitter region. Diode parameters obtained from I sub sc - V sub oc plots, data from surface Raman spectroscopy, and determinations of surface conductivity types are used to investigate the configuration of the ITO/InP cells. It is concluded that thesee latter cells are n/p homojunctions, the n-region consisting of a disordered layer at the oxide semiconductor

A double junction model of irradiated silicon pixel sensors for LHC

In this paper we discuss the measurement of charge collection in irradiated silicon pixel sensors and the comparison with a detailed simulation. The simulation implements a model of radiation damage by including two defect levels with opposite charge states and trapping of charge carriers. The modeling proves that a doubly peaked electric field generated by the two defect levels is necessary to describe the data and excludes a description based on acceptor defects uniformly distributed across the sensor bulk. In addition, the dependence of trap concentrations upon fluence is established by comparing the measured and simulated profiles at several fluences and bias voltages.Comment: Talk presented at the 10th European Symposium on Semiconductor Detectors, June 12-16 2005, Wildbad Kreuth, Germany. 9 pages, 4 figure

The optimal polarizations for achieving maximum contrast in radar images

There is considerable interest in determining the optimal polarizations that maximize contrast between two scattering classes in polarimetric radar images. A systematic approach is presented for obtaining the optimal polarimetric matched filter, i.e., that filter which produces maximum contrast between two scattering classes. The maximization procedure involves solving an eigenvalue problem where the eigenvector corresponding to the maximum contrast ratio is an optimal polarimetric matched filter. To exhibit the physical significance of this filter, it is transformed into its associated transmitting and receiving polarization states, written in terms of horizontal and vertical vector components. For the special case where the transmitting polarization is fixed, the receiving polarization which maximizes the contrast ratio is also obtained. Polarimetric filtering is then applies to synthetic aperture radar images obtained from the Jet Propulsion Laboratory. It is shown, both numerically and through the use of radar imagery, that maximum image contrast can be realized when data is processed with the optimal polarimeter matched filter

Photon trapping and energy transfer in multiple-dye plastic matrices: an efficient solar-energy concentrator

Experiments are described illustrating enhanced photon trapping and efficient energy transfer in mixed-dye planar solar concentrators containing, for example, Rhodamine 6G and Coumarin 6. These concentrators intercept more of the solar spectrum to give an enhanced photon-flux gain that exceeds the single-dye concentrator. It is also shown that the energy absorbed by the donor dye is transferred efficiently into the emitting acceptor by two competing processes

Lattice-dynamics of a Disordered solid-solid Interface

Generic properties of elastic phonon transport at a disordered interface are studied. The results show that phonon transmittance is a strong function of frequency and the disorder correlation length. At frequencies lower than the van Hove singularity the transmittance at a given frequency increases as the correlation length decreases. At low frequencies, this is reflected by different power-laws for phonon conductance across correlated and uncorrelated disordered interfaces which are in approximate agreement with perturbation theory of an elastic continuum. These results can be understood in terms of simple mosaic and two-colour models of the interface.Comment: 17 pages, 5 figures, submitted to PR