2,106 research outputs found
Physics at Future Linear Colliders
This article summarises the physics at future linear colliders. It will be
shown that in all studied physics scenarios a 1 TeV linear collider in addition
to the LHC will enhance our knowledge significantly and helps to reconstruct
the model of new physics nature has chosen.Comment: Invited talk at the Lepton Photon Symposium 2005, Upsala, Sweden,
July 2005, V2: minor improvement
A multipurpose laboratory diffractometer for operando powder X-ray diffraction investigations of energy materials
Laboratory X-ray diffractometers are among the most widespread instruments in research laboratories around the world and are commercially available in different configurations and setups from various manufacturers. Advances in detector technology and X-ray sources push the data quality of in-house diffractometers and enable the collection of time-resolved scattering data during operando experiments. Here, the design and installation of a custom-built multipurpose laboratory diffractometer for the crystallographic characterization of battery materials are reported. The instrument is based on a Huber six-circle diffractometer equipped with a molybdenum microfocus rotating anode with 2D collimated parallel-beam X-ray optics and an optional two-bounce crystal monochromator. Scattered X-rays are detected with a hybrid single-photon-counting area detector (PILATUS 300K-W). An overview of the different diffraction setups together with the main features of the beam characteristics is given. Example case studies illustrate the flexibility of the research instrument for time-resolved operando powder X-ray diffraction experiments as well as the possibility to collect higher-resolution data suitable for diffraction line-profile analysis
QCD corrections to the forward-backward asymmetries of and quarks at the Z pole
Measurements of the forward-backward production asymmetry of heavy quarks in Z decays provide a precise determination of \swsqeffl . The asymmetries are sensitive to QCD effects, in particular hard gluon radiation. In this paper QCD corrections for \AFBbb~ and \AFBcc~ are discussed. The interplay between the experimental techniques used to measure the asymmetries and the QCD effects is investigated using simulated events. A procedure to estimate the correction needed for experimental measurements is proposed, and some specific examples are given
Electroweak Physics, Experimental Aspects
Collider measurements on electroweak physics are summarised. Although the
precision on some observables is very high, no deviation from the Standard
Model of electroweak interactions is observed. The data allow to set stringent
limits on some models for new physics.Comment: Plenary Talk at the UK Phenomenology Workshop on Collider Physics,
Durham, 199
LiCaFeF6 A zero strain cathode material for use in Li ion batteries
A new zero strain LiCaFeF6 cathode material for reversible insertion and extraction of lithium ions is presented. LiCaFeF6 is synthesized by a solid state reaction and processed to a conductive electrode composite via high energy ball milling. In the first cycle, a discharge capacity of 112 mAh g amp; 8315; is achieved in the voltage range from 2.0 V to 4.5 V. The electrochemically active redox couple is Fe3 amp; 8314; Fe2 amp; 8314; as confirmed by Mössbauer spectroscopy and X ray absorption spectroscopy. The compound has a trigonal colquiriite type crystal structure space group . By means of in situ and ex situ XRD as well as X ray absorption fine structure spectroscopy a reversible response to Li uptake release is found. For an uptake of 0.8 mol Li per formula unit only minimal changes occur in the lattice parameters causing a total change in unit cell volume of less than 0.5 . The spatial distribution of cations in the crystal structure as well as the linkage between their corresponding fluorine octahedra is responsible for this very small structural response. With its zero strain behaviour this material is expected to exhibit only negligible mechanical degradation. It may be used as a cathode material in future lithium ion batteries with strongly improved safety and cycle lif
Depth profile analyses of films grown at different temperatures
Cu(In,Ga)Se2films are used as absorber layers in chalcopyrite thin filmsolar
cells. As the gallium concentration in the absorber can be used to control the
band gap, there have been many efforts to vary the gallium concentration in
depth to gain an optimum balance of light absorption, carrier collection, and
recombination at different depths of the absorber film, leading to improved
quantum efficiency. In this study, we investigate the effect of the maximum
substrate temperature during film growth on the depth dependent gallium
concentration. For the in-depth gallium concentration analyses, we use two
techniques, covering complementary depth ranges. Angle dependent soft x-ray
emission spectroscopy provides access to information depths between 20 and 470
nm, which covers the depth range of the space charge region, where most of the
photoexcited carriers are generated. Therefore, this depth range is of
particular interest. To complement this investigation we use secondary neutral
mass spectrometry, which destructively probes the whole thickness of the
absorber (â2âÎŒm). The two methods show increasingly pronounced gallium and
indium gradients with decreasing maximum substrate temperature. The probing of
the complementary depth ranges of the absorbers gives a consistent picture of
the in-depth gallium distribution, which provides a solid basis for a
comprehensive discussion about the effect of a reduced substrate temperature
on the formation of gallium gradients in Cu(In,Ga)Se2 and the device
performance of the corresponding reference solar cells
Calculation of the Two-Loop Heavy-Flavor Contribution to Bhabha Scattering
We describe in detail the calculation of the two-loop corrections to the QED
Bhabha scattering cross section due to the vacuum polarization by heavy
fermions. Our approach eliminates one mass scale from the most challenging part
of the calculation and allows us to obtain the corrections in a closed
analytical form. The result is valid for arbitrary values of the heavy fermion
mass and the Mandelstam invariants, as long as s,t,u >> m_e^2.Comment: 43 pages, 8 figures; added reference
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