2,993 research outputs found

    Studies of the Linearity of the ATLAS EM Barrel Calorimeter

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    The ATLAS experiment uses an accordion shaped lead/liquid argon sampling calorime- ter for electromagnetic calorimetry. During beam test campaigns in summer 2002 and summer 2004 dedicated linearity scans were carried out. During the 2004 run, not only the beam energy but also the material in front of the calorimeter has been varied. This contribution discusses methods to achieve an excellent linearity and resolution even in the presence of a significant amount of upstream material. These methods were developed and tested on data obtained from the described beam tests and on a Geant4 simulation of the beam test setup

    Digitization of LAr calorimeter for CSC simulations

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    This note describes the digitization of the LAr signals, which is the step creating RDO from Geant4 Hits, as used during the production of the CSC simulated samples with athena release 12

    2004 ATLAS Combined Testbeam : Computation and Validation of the Electronic Calibration Constants for the Electromagnetic Calorimeter

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    From July to November 2004, a full slice of the ATLAS barrel detector was studied in testbeam. A complete electromagnetic barrel module was used, read by the final electronics and operated by ATLAS TDAQ software. This note describes in details the electronic calibration procedure and the cell energy reconstruction: each step of the procedure and its associated software is explicitly described. The general calibration procedure is very similar to the one applied in previous barrel and endcap standalone testbeams. Emphasis is put on tools developed in the context of the combined testbeam which can be used for commissioning and operation of the calorimeters in ATLAS. Many validation studies were performed on each calibration constant. Previously unobserved effects such as the FEB temperature dependence of some constants were observed. Overall, the calibration performances are at the expected level

    Calorimeter Clustering Algorithms: Description and Performance

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    This note describes the performance of the calorimeter clustering algorithms used for ATLAS, and which provide inputs for particle identification. ATLAS uses two principal algorithms. The first is the ``sliding-window'' algorithm, which clusters calorimeter cells within fixed-size rectangles; results from this are used for electron, photon, and tau lepton identification. The second is the ``topological'' algorithm, which clusters together neighboring cells, as long as the signal in the cells is significant compared to noise. The results of this second algorithm are further used for jet and missing transverse energy reconstruction. This note first summarizes the steps of the calorimeter reconstruction software. A detailed description of the two clustering algorithms is then given. A last section summarizes their performance. The results presented in this note are obtained with the ATLAS athena software releases 12 and 13

    IL-23-mediated mononuclear phagocyte crosstalk protects mice from Citrobacter rodentium-induced colon immunopathology.

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    Gut homeostasis and mucosal immune defense rely on the differential contributions of dendritic cells (DC) and macrophages. Here we show that colonic CX3CR1(+) mononuclear phagocytes are critical inducers of the innate response to Citrobacter rodentium infection. Specifically, the absence of IL-23 expression in macrophages or CD11b(+) DC results in the impairment of IL-22 production and in acute lethality. Highlighting immunopathology as a death cause, infected animals are rescued by the neutralization of IL-12 or IFNő≥. Moreover, mice are also protected when the CD103(+) CD11b(-) DC compartment is rendered deficient for IL-12 production. We show that IL-12 production by colonic CD103(+) CD11b(-) DC is repressed by IL-23. Collectively, in addition to its role in inducing IL-22 production, macrophage-derived or CD103(-) CD11b(+) DC-derived IL-23 is required to negatively control the otherwise deleterious production of IL-12 by CD103(+) CD11b(-) DC. Impairment of this critical mononuclear phagocyte crosstalk results in the generation of IFNő≥-producing former TH17 cells and fatal immunopathology

    Stimulus - response curves of a neuronal model for noisy subthreshold oscillations and related spike generation

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    We investigate the stimulus-dependent tuning properties of a noisy ionic conductance model for intrinsic subthreshold oscillations in membrane potential and associated spike generation. On depolarization by an applied current, the model exhibits subthreshold oscillatory activity with occasional spike generation when oscillations reach the spike threshold. We consider how the amount of applied current, the noise intensity, variation of maximum conductance values and scaling to different temperature ranges alter the responses of the model with respect to voltage traces, interspike intervals and their statistics and the mean spike frequency curves. We demonstrate that subthreshold oscillatory neurons in the presence of noise can sensitively and also selectively be tuned by stimulus-dependent variation of model parameters.Comment: 19 pages, 7 figure
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