110352212
Energy reconstruction for a hadronic calorimeter using neural networks
Abstract Often calorimeters have a non-compensating response ( e / h ≠ 1 ) . Non-compensation degrades both resolution and linearity figures. To improve on this, weighting techniques are frequently applied. These techniques normally use linear combination of the energy deposited in the calorimeter cells or longitudinal samples. For the hadronic calorimeter of ATLAS, Tilecal, the use of a neural network is proposed to perform the energy reconstruction for pions, taking into account both linearity and energy resolution. Experimental data from testbeam periods were used to perform neural reconstruction.
118662023
Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics
A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.
17177612
The optical instrumentation of the ATLAS Tile Calorimeter
The Tile Calorimeter, covering the central region of the ATLAS experiment up to pseudorapidities of +/-1.7, is a sampling device built with scintillating tiles that alternate with iron plates. The ...
108026736
A hybrid training method for neural energy estimation in calorimetry
A neural mapping is developed to improve the overall performance of Tilecal, which is the hadronic calorimeter of the ATLAS detector. Feeding the input nodes of a multilayer feedforward neural network with the energy values sampled by the calorimeter cells in beam tests, it is shown that the original energy scale of pion beams is reconstructed over a wide energy range and linearity is significantly improved. As it happens for classical methods, a compromise between nonlinearity correction and the optimization of the energy resolution of the detector has to be accomplished. A hybrid training method for the neural mapping is proposed to achieve this design goal. Using the back-propagation algorithm, the method intercalates an epoch of training steps, for which the neural mapping mainly focus on linearity correction, with another block of training steps, in which the original energy resolution obtained by linearly combining the calorimeter cells becomes the main target.
66116773
A mobile data acquisition system
A mobile data aquisition (MobiDAQ) was developed for the ATLAS central hadronic calorimeter (TileCal). MobiDAQ has been designed in order to test the functionalities of the TileCal front-end electronics and to acquire calibration data before the final back-end electronics were built and tested. MobiDAQ was also used to record the first cosmic ray events acquired by an ATLAS subdetector in the underground experimental area.
96502755
Charged-particle multiplicities inppinteractions measured with the ATLAS detector at the LHC
New Journal of Physics The open–access journal for physics Charged-particle multiplicities in pp interactions measured with the ATLAS detector at the LHC The ATLAS Collaboration New Journal of Physics 13 (2011) 053033 (68pp) Received 22 December 2010 Published 19 May 2011 Online at http://www.njp.org/ doi:10.1088/1367-2630/13/5/053033 Measurements √ are presented from proton–proton collisions at centre-of-mass energies of s = 0.9, 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum- bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared to each other and to various Monte Carlo (MC) models, including a new AMBT1 pythia6 tune. In all the kinematic regions considered, the particle multiplicities are higher than predicted by the MC models. The central charged-particle multiplicity per event and unit of pseudorapidity, for tracks √ with p T > 100 MeV, is measured to be 3.483 ± 0.009 (stat) (syst) at s = 0.9 TeV and 5.630 ± 0.003 (stat) ± 0.169 (syst) at s = 7 TeV. Abstract. New Journal of Physics 13 (2011) 053033 © 2011 CERN for the benefit of the ATLAS Collaboration, published under licence by IOP Publishing Ltd for the Institute of Physics and Deutsche Physikalische Gesellschaft. Content may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation and DOI.
119480251
Generalized Chaplygin gas model, supernovae, and cosmic topology
In this work we study to which extent the knowledge of spatial topology may place constraints on the parameters of the generalized Chaplygin gas (GCG) model for unification of dark energy and dark matter. By using both the Poincar\'e dodecahedral and binary octahedral spaces as the observable spatial topologies, we examine the current type Ia supernovae (SNe Ia) constraints on the GCG model parameters. We show that the knowledge of spatial topology does provide additional constraints on the ${A}_{s}$ parameter of the GCG model but does not lift the degeneracy of the $\ensuremath{\alpha}$ parameter.
118693161
On the rise of proton-proton cross-sections at high energies
The rise of total, elastic and inelastic hadronic cross sections at high energies is investigated by means of an analytical parametrization, with the exponent of the leading logarithm contribution as a free fit parameter. Using derivative dispersion relations with one subtraction, two different fits to proton–proton and antiproton–proton total cross section and ρ parameter data are developed, reproducing well the experimental information in the energy region 5 GeV–7 TeV. The parametrization for the total cross sections is then extended to fit the elastic (integrated) cross section data in the same energy region, with satisfactory results. From these empirical results we extract the energy dependence of several physical quantities: inelastic cross section, ratios elastic/total, inelastic/total cross sections, ratio total-cross-section/elastic-slope, elastic slope and optical point. All data, fitted and predicted, are quite well described. We find a statistically consistent solution indicating: (1) an increase of the hadronic cross sections with the energy faster than the log-squared bound by Froissart and Martin; (2) asymptotic limits 1/3 and 2/3 for the ratios elastic/total and inelastic/total cross sections, respectively; a result in agreement with unitarity. These indications corroborate recent theoretical arguments by Azimov on the rise of the total cross section.
33567845
The CMS Electromagnetic Calorimeter Data Acquisition System at the 2006 Test Beam.
The electromagnetic calorimeter of the CMS experiment at CERN is an homogeneous calorimeter made of about 80000 Lead Tungstate crystals, that will start to operate at the LHC at the end of 2007. From June to November 2006, ten barrel Supermodules (1700 crystals each) were exposed to beam at CERN SPS, both in standalone and in association with portions of the Hadron Calorimeter. We present the description of the system used to configure and readout the calorimeter during the campaign. The full set of final readout electronics boards was employed, together with the pre-series version of the data acquisition software. During the campaign, the hardware and software concepts for the final system were validated. The system allowed the intercalibration of the ten Supermodules and allowed to perform several important studies of the detector performances, such as energy resolution, response linearity and radiation-hardness.
30333745
First beam operation of the CMS calorimeter trigger synchronization boards
The CMS experiment uses information from its electromagnetic and hadronic calorimeters and muon detectors to decide whether to readout the whole detector. For such a task to be successful, all trigger primitives pushed through the trigger decision tree must be flawlessly aligned in time for operation at 40 MHz. Both calorimeters in CMS use the Synchronization Link Board for this purpose. In this article we report on the results of tests of this board using realistic beam conditions, which demonstrate the soundness of the adopted architecture and synchronization principle.
15081043
Fixed points and vacuum energy of dynamically broken gauge theories
We show that if a gauge theory with dynamical symmetry breaking has nontrivial fixed points, they will correspond to extrema of the vacuum energy. This relationship provides a different method to determine fixed points.