133716710
New applications of silicon micromachining
The use of photolithography and anisotropic etching of silicon wafers to make strong, thin membranes has created a large family of miniature sensing devices such as pressure transducers and accelerometers. This report describes several entirely new devices in which silicon membranes are used for their strength and for their transparency to certain kinds of radiation. Two applications are described: a rugged alpha detector and a fluid sample cell for small-angle x-ray scattering. 8 refs., 12 figs., 2 tabs.
111231498
Effects of radiation on scintillating fiber performance
Continued rapid improvements in formulations for scintillating fibers require the ability to parameterize and predict effects of radiation on detector performance. Experimental techniques necessary to obtain desired information and calculation procedures used in performing predications for hadron scintillating fiber calorimetry in the Superconducting Super Collider environment are described. The experimental techniques involve control of the testing environment, consideration of dose rate effects. and other factors. The calculations involve the behavior of particle showers in the detector, expected levels of radiation, and parameterization of the radiation effects. A summary of significant work is presented. >
107502491
Bipolar monolithic preamplifiers for SSC silicon calorimetry
This paper describes preamplifiers designed specifically to address the requirements of silicon calorimetry for the Superconducting Super Collider (SSC). Eight different preamplifiers designed for detector capacitances ranging from 20 pF to 500 pF and operating temperatures from 25{degree}C to {minus}20{degree}C are discussed. The preamplifiers were fabricated with two different high-frequency processes (one with the VTC, Inc. VJ900 process, seven with the Harris Semiconductor VHF Process). The different topologies and their features are discussed in addition to the design methodologies employed. The results for noise, power consumption, speed, and radiation damage effects as well as data for post-damage annealing are presented for the VTC process preamplifier. Simulations for the VHF Process circuits are presented. This work was funded through SSC Generic Detector funding, SSC Detector Subsystem funding, and the Oak Ridge National Laboratory (ORNL) Detector Center.
110822912
Monolithic systems design for the Silicon Electromagnetic Calorimetry Collaboration
A series of monolithic bipolar charge-sensitive preamplifiers and a companion monolithic 50-ns CMOS shaping amplifier have been designed, fabricated, and characterized for use with silicon calorimeters. The preamplifier topologies evaluated were current-mode, folded cascode, and differential. These three topologies were fabricated in the Harris Semiconductor VHF process and were characterized for noise, transient response, power dissipation and radiation hardness. Versions of each preamplifier have been designed to operate over a range of detector pad capacitance from 20-500 pF. The CMOS shaping amplifier specifications and test results are presented with emphasis on the system integration requirements for beam tests. >
120285322
SIMULATION OF SHIELDING DESIGNS FOR FUTURE LARGE-SCALE DARK MATTER SEARCH EXPERIMENTS
4976848
Exotic leptons: Higgs, flavor and collider phenomenology
A bstractWe study extensions of the standard model by one generation of vector-like leptons with non-standard hypercharges, which allow for a sizable modification of the h → γγ decay rate for new lepton masses in the 300 GeV-1 TeV range. We analyze vacuum stability implications for different hypercharges. Effects in h → Zγ are typically much smaller than in h → γγ, but distinct among the considered hypercharge assignments. Non-standard hypercharges constrain or entirely forbid possible mixing operators with standard model leptons. As a consequence, the leading contributions to the experimentally strongly constrained electric dipole moments of standard model fermions are only generated at the two loop level by the new CP violating sources of the considered setups. We derive the bounds from dipole moments, electro-weak precision observables and lepton flavor violating processes, and discuss their implications. Finally, we examine the production and decay channels of the vector-like leptons at the LHC, and find that signatures with multiple light leptons or taus are already probing interesting regions of parameter space.
115160247
Another derivation of the geometrical KPZ relations
We give a physicist's derivation of the geometrical (in the spirit of Duplantier–Sheffield) KPZ relations, via heat kernel methods. It gives a covariant way to define neighborhoods of fractals in 2D quantum gravity, and shows that these relations are in the realm of conformal field theory.
121526925
EURECA: The European future of dark matter searches with cryogenic detectors
EURECA (European Underground Rare Event Calorimeter Array) is a new project, searching for dark matter, with largely the present groups of the CRESST and EDELWEISS experiments and already a few new groups. The aim is to explore scalar cross sections in the 10 −9 –10 −10 picobarn region with a target mass of up to one tonne. A major advantage of EURECA is our planned use of more that just one target material (multi target experiment for WIMP identification). In preparation for this large-scale experiment, R&D for EURECA is provided through the current phases of CRESST and EDELWEISS.
118512166
Top-quark forward-backward asymmetry in Randall-Sundrum models beyond the leading order
We calculate the $ t\overline t $ forward-backward asymmetry, AtFB, in Randall-Sundrum (RS) models taking into account the dominant next-to-leading order (NLO) corrections in QCD. At Born level we include the exchange of Kaluza-Klein (KK) gluons and photons, the Z boson and its KK excitations, as well as the Higgs boson, whereas beyond the leading order (LO) we consider the interference of tree-level KK-gluon exchange with one-loop QCD box diagrams and the corresponding bremsstrahlungs corrections. We find that the strong suppression of LO effects, that arises due to the elementary nature and the mostly vector-like couplings of light quarks, is lifted at NLO after paying the price of an additional factor of αs/(4π). In spite of this enhancement, the resulting RS corrections in AtFB remain marginal, leaving the predicted asymmetry SM-like. As our arguments are solely based on the smallness of the axial-vector couplings of light quarks to the strong sector, our findings are model-independent and apply to many scenarios of new physics that address the flavor problem via geometrical sequestering.