Analysis of trap spectra in LEC and epitaxial GaAs

Different methods of trap parameter measurement are analysed. Transient photoconductivity and thermally stimulated effects were used to investigate the influence of traps in LEC SI-GaAs and high resistivity epitaxial GaAs. The peculiarities of the TSC were analysed and shown to be related to the influence of crystal micro-inhomogeneities.Comment: Invited talk, 6-th Workshop on Gallium Arsenide and Related Compounds June 22-26, 1998 Praha-Pruhonice, Czech Republi

Effect of western juniper on understory herbage production in Central Oregon

Evidence suggests that western juniper (Juniperus occidentalis) in Central Oregon affects understory production and composition. As trees increase in size and density, understory production is reduced and composition changes. This study was designed to identify the relationship between production and composition of understory vegetation and various tree canopy sizes of western juniper, and to describe the responses of understory vegetation to removal of western juniper. Understory production was sampled in 1983 and 1984 by clipping plots on an individual trees basis from areas with trees present and areas from which trees had been removed in 1982. Biomass production was determined from trees within three canopy diameter size classes and from two zones, beneath the canopy and in the interspace. Production was examined on two sites, a lower slope, shallow soil site and an upper slope, moderately deep soil site. Some year-to-year differences in production of individual species and specific tree sizes may be explained by variation in precipitation during critical growth periods the two years of the study. Sandberg bluegrass and, possibly, Idaho fescue production may have been greater in 1983 than 1984 due to variation in late spring precipitation, especially on shallow soils associated with small trees. Differences in patterns of production of individual species were most clearly developed associated with large, rather than small and intermediate trees. Cheatgrass, squirreltail, bluebunch wheatgrass, and Idaho fescue were common beneath the canopy, while Sandberg bluegrass was common in the interspaces. Cheatgrass and perennial forb production beneath the canopy increased with tree size. Production of other species, such as Sandberg bluegrass, was apparently not affected by tree size. Canopy removal resulted in species-specific increases in biomass production both years. Production increases were greater beneath the canopy than in the interspaces. Perennial grasses provided small variable production increases beneath the canopy of large trees. Annual grasses, primarily cheatgrass, and annual forbs, primarily Epilobium paniculatum, contributed most to elevated productivity the first two years following juniper removal. Cheatgrass response was mainly associated with large trees, while annual forb response was independent of tree size. Sandberg bluegrass production seemed more closely tied to growing season precipitation than to canopy removal, regardless of tree size

A quantum algorithm for solving open system dynamics on quantum computers using noise

In this paper we present a quantum algorithm that uses noise as a resource. The goal of our quantum algorithm is the calculation of operator averages of an open quantum system evolving in time. Selected low-noise system qubits and noisy bath qubits represent the system and the bath of the open quantum system. All incoherent qubit noise can be mapped to bath spectral functions. The form of the spectral functions can be tuned digitally, allowing for the time evolution of a wide range of open-system models at finite temperature. We study the feasibility of this approach with a focus on the solution of the spin-boson model and assume intrinsic qubit noise that is dominated by damping and dephasing. We find that classes of open quantum systems exist where our algorithm performs very well, even with gate errors as high as 1%. In general the presented algorithm performs best if the system-bath interactions can be decomposed into native gates.Comment: 19 pages, 8 figures in total: 10 pages main text with 7 figure

High rate, fast timing Glass RPC for the high {\eta} CMS muon detectors

The HL-LHC phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. To achieve this goal in a reasonable time scale the instantaneous luminosity would also increase by an order of magnitude up to $6.10^{34} cm^{-2} s^{-1}$ . The region of the forward muon spectrometer ($|{\eta}| > 1.6$) is not equipped with RPC stations. The increase of the expected particles rate up to $2 kHz/cm^{2}$ (including a safety factor 3) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The actual RPC technology of CMS cannot sustain the expected background level. The new technology that will be chosen should have a high rate capability and provides a good spatial and timing resolution. A new generation of Glass-RPC (GRPC) using low-resistivity (LR) glass is proposed to equip at least the two most far away of the four high ${\eta}$ muon stations of CMS. First the design of small size prototypes and studies of their performance in high-rate particles flux is presented. Then the proposed designs for large size chambers and their fast-timing electronic readout are examined and preliminary results are provided.Comment: 14 pages, 11 figures, Conference proceeding for the 2016 Resistive Plate Chambers and Related Detector

Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum