8618294
Development of a high-rate GEM-based TPC for PANDA
An ungated GEM-based TPC with continuous readout is considered as the central tracker of the PANDA experiment. Particles from up to 2ldr107 p macrp annih./s have to be tracked over a wide momentum range (0.1-8 GeV/c). Simulations demonstrate a space charge accumulation of up to 55 fC/cm3, leading to correctable track distortions of up to 6 mm. Ion backflow studies in triple-GEM structures have been performed. A spatial resolution of down to 140 mum has been achieved with a GEM-TPC test chamber, operated with an Ar/CO2 gas mixture and without magnetic field, recording the signals of cosmic muons.
119280331
Calorimeter-Based Triggers at the ATLAS Detector for Searches for Supersymmetry in Zero-Lepton Final States
This thesis consists of three closely related parts. An analysis of data recorded by the ATLAS detector in 2010 in proton-proton collisions at a center-of-mass energy of 7 TeV with an integrated luminosity of 33.4 pb-1 is performed, searching for supersymmetric final states containing jets and missing transverse energy and no electrons or muons (zero-lepton channel). No excess over the Standard Model background expectation is observed. Using the CLs and PLR methods, exclusion limits are set in a minimal supergravity model with tan β = 3, A0 = 0 GeV and μ > 0 and in a simplified supergravity model. These considerably extend the excluded parameter ranges from earlier experiments. The analysis validates the official analysis carried out within the ATLAS Supersymmetry group and additionally takes into account the uncertainty from pile-up effects.The rates and efficiencies of triggers based on combined signatures with jets plus missing transverse energy in ATLAS are studied, which are the primary triggers for the search for Supersymmetry in the zero-lepton channel. Methods to measure the efficiencies on data are tested and optimized to obtain sufficient statistics. For the measurement of the efficiencies in data collected in 2010 and 2011, the bootstrap method is applied to correct for the sample trigger bias. Different sample triggers based on jets and missing transverse energy are compared and their efficiencies are measured. A reweighting approach is studied and used to correct for the bias from the propagation of the uncertainties in the bootstrap method. The resulting efficiency estimates for the primary triggers allow to determine the onset of the plateau of the two-dimensional turn-on curves and are input to the official analyses in the ATLAS Supersymmetry group in 2010 and 2011.A universal model is developed to describe the contribution of fake missing transverse energy from resolution effects to the rates of missing transverse energy triggers as function of the level of in-time pile-up, i.e. the number of concurrent proton-proton interactions. The input parameters to tune the model to the properties of the ATLAS triggers are determined, and the model predictions are compared to measurements of trigger rates in ATLAS. Good agreement is found for missing transverse energy triggers with low thresholds for which the rates are dominated by resolution effects, whereas the rates for higher thresholds are underestimated due to additional sources of fake and real missing transverse energy which are not incorporated in the model.
20903628
Repulsive Casimir forces.
We discuss repulsive Casimir forces between dielectric materials with nontrivial magnetic susceptibility. It is shown that considerations based on the naive pairwise summation of van der Waals and Casimir-Polder forces may not only give an incorrect estimate of the magnitude of the total Casimir force but even the wrong sign of the force when materials with high dielectric and magnetic responses are involved. Indeed repulsive Casimir forces may be found in a large range of parameters, and we suggest that the effect may be realized in known materials. The phenomenon of repulsive Casimir forces may be of importance both for experimental study and for nanomachinery applications.
123016244
Observation of new particle production by high energy neutrinos and antineutrinos
122141713
A liquid-scintillator total-absorption hadron calorimeter for the study of neutrino interactions
Abstract We describe the performance of a large-volume liquid-scintillator calorimeter which has been used to measure the total energy of hadrons produced by interactions of neutrinos with nucleons. The resolution of the calorimeter is about 12% rms for incident pions over the energy range 20–150 GeV, and about 15% for neutrino-induced hadron systems in the chosen fiducial volume after corrections for imperfect energy containment.
120319912
A large-area magnetic spectrometer for the study of high-energy neutrino interactions
Abstract We describe the design, construction, and performance of a large solid iron magnetic spectrometer which has been used to i dentify and measure the momentum of muons produced by interactions of neutrinos with nucleons. The rms momentum resolution varies from 10 to 15 percent between 5 and 150 GeV/ c .
121620440
Study of Approximations in the Nuclear Pairing-Force Problem