110325204
Upgrade of the Readout Electronics of the ATLAS MDT Detector for SLHC
Simulation predicts a high level of ionizing radiation in the ATLAS experimental hall during LHC operation. This radiation will act as a source of background signals to the four subsystems of the ATLAS muon detector. We present the performance of the Monitored Drift Tube detector (MDT) under these background conditions and discuss the consequences for the much higher background rates at SLHC with respect to tracking efficiency, resolution and readout bandwidth. For rates beyond the expected LHC levels, we discuss options to improve the performance of detector and electronics.
120421514
GAS SYSTEM FOR ALEPH TPC
Abstract Operation of the time projection chamber of the ALEPH experiment at LEP requires a high-purity argon/methane gas mixture supplied to the detector under stable conditions to ensure minimum signal attenuation throughout the 43 m 3 detector volume (max. 2.2 m drift length) and maintain near-constant electron drift velocity in the gas over extended periods of time. Design considerations for a gas system to fulfil these conditions are presented and details given of the construction, operational aspects and of the achieved performance.
108271361
Concepts for the readout of time projection chambers
While the use of CCD’s for the readout of TPC’s offers a reliable and ever more of the digitization concept. The problem of precision of currently available FADC’s is discussed together with two proposals for a solution.
122359864
Large-scale production of Monitored Drift Tube chambers for the ATLAS muon spectrometer
Abstract Precision drift tube chambers with a sense wire positioning accuracy of better than 20 μm are under construction for the ATLAS muon spectrometer. 70% of the 88 large chambers for the outermost layer of the central part of the spectrometer have been assembled. Measurements during chamber construction of the positions of the sense wires and of the sensors for the optical alignment monitoring system demonstrate that the requirements for the mechanical precision of the chambers are fulfilled.
120324718
Integration, commissioning and installation of monitored drift tube chambers for the ATLAS barrel muon spectrometer
The ATLAS experiment at the Large Hadron Collider (LHC) at CERN is currently being assembled to be ready to take data in 2007. Its muon spectrometer is designed to achieve a momentum resolution better than 10% at 1 TeV. In the barrel part, a toroidal air-core magnet is instrumented with three layers of Monitored Drift Tube (MDT) chambers for precision tracking. The Max-Planck-Institut fur Physik and the Ludwig-Maximilians-University in Munich have built 88 MDT chambers for the outermost barrel layer. We report on our experience with the tests of the MDT chambers, their integration with the Resistive Plate trigger chambers and the installation of the muon stations in the experiment. First results of their commissioning in the ATLAS detector will be presented.
126243744
Measurement of the reaction π−p→π+π−n on a transversely polarized target at 17.2 GeV
Preliminary results from a high statistics measurement (1 M events) of the reaction π−p→π+π−n on strong polarization effects which must be attributed to amplitudes corresponding to ’’A1’’ exchange.
55147901
Light stringy states
A bstractWe carefully study the spectrum of open strings localized at the intersections of D6-branes and identify the lowest massive ‘twisted’ states and their vertex operators, paying particular attention to the signs of the intersection angles. We argue that the masses of the lightest states scale as $ M_{\theta }^2 \approx \theta M_s^2 $ and can thus be parametrically smaller than the string scale. Relying on previous analyses, we compute scattering amplitudes of massless ‘twisted’ open strings and study their factorization, confirming the presence of the light massive states as sub-dominant poles in one of the channels.
110599112
Sensor design for the ATLAS-pixel detector
Abstract The inner detector of the ATLAS experiment will contain three layers of pixel detectors. The first prototype of the sensor part will be an n + n-device in order to allow partial depleted operation after bulk inversion and a guard-ring scheme keeping the entire detector surface close to the electronic chip on ground potential. Further, a bias structure is introduced providing testability of the sensors before mounting them to the electronics. The design of the single pixel cell is the result of a detailed device simulation study.
110917125
Radiation hard strip detectors for large-scale silicon trackers
Abstract Major challenges in building silicon strip detectors for future high luminosity experiments are the high radiation level and the huge number of sensors required for the construction of the precision layers of the complete tracking system. Single-sided p + n strip detectors for ATLAS SCT designed and fabricated at the MPI Semiconductor Laboratory have been exposed to 3×10 14 /cm 2 24 GeV protons. The major features of the design, including the biasing technique using implanted resistors, are discussed and results are presented. The technology was transferred to CiS, Germany, a company capable of the desired large-scale production. Results of this industrially fabricated sensors look very promising and show the expected radiation hardness.
16346923
(Non-)BPS bound states and D-brane instantons
We study non-perturbative effects in four-dimensional = 1 supersymmetric orientifold compactifications due to D-brane instantons which are not invariant under the orientifold projection. We show that they can yield superpotential contributions via a multi-instanton process at threshold. Some constituents of this configuration form bound states away from the wall of marginal stability which can decay in other regions of moduli space. A microscopic analysis reveals how contributions to the superpotential are possible when new BPS states compensate for their decay. We study this concretely for D2-brane instantons along decaying special Lagrangians in Type IIA and for D5-branes instantons carrying holomorphic bundles in Type I theory.
120631402
Characterization of silicon microstrip detectors using an infrared laser system
Abstract An infrared laser system with variable wavelength is used to study fundamental properties of silicon microstrip detectors. Results of measurements concerning charge sharing among adjacent readout strips and depletion mapping are presented. The results are interpreted in a model framework which describes the charge sharing with the help of the so-called η -function. The wavelength dependence of the η -function is studied. Surface effects important for short wavelengths are observed.