Showing papers by "Christopher Lester published in 2008"
Posted Content•
TL;DR: In this article, a detailed study of the expected performance of the ATLAS detector is presented, together with the reconstruction of tracks, leptons, photons, missing energy and jets, along with the performance of b-tagging and the trigger.
Abstract: 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.
1,160 citations
TL;DR: In this article, the authors considered the problem of mass determination for new particles produced at a hadron collider, where these particles decay to an invisible particle of unknown mass and one or more visible particles of known mass.
Abstract: We consider the application of endpoint techniques to the problem of mass determination for new particles produced at a hadron collider, where these particles decay to an invisible particle of unknown mass and one or more visible particles of known mass. We also consider decays of these types for pair-produced particles and in each case consider situations both with and without initial state radiation. We prove that, in most (but not all) cases, the endpoint of an appropriate transverse mass observable, considered as a function of the unknown mass of the invisible particle, has a kink at the true value of the invisible particle mass. The co-ordinates of the kink yield the masses of the decaying particle and the invisible particle. We discuss the prospects for implementing this method at the LHC.
182 citations
TL;DR: In this paper, the authors consider well-motivated examples in supersymmetry with both gravity and gauge mediation and build nonminimally flavor violating models that successfully explain all known lepton masses and mixings, but span a wide range in their predictions for slepton flavor violation.
Abstract: Can the Large Hadron Collider explain the masses and mixings of the known fermions? A promising possibility is that these masses and mixings are determined by flavor symmetries that also govern new particles that will appear at the LHC. We consider well-motivated examples in supersymmetry with both gravity and gauge mediation. Contrary to spreading belief, new physics need not be minimally flavor violating. We build nonminimally flavor violating models that successfully explain all known lepton masses and mixings, but span a wide range in their predictions for slepton flavor violation. In natural and favorable cases, these models have metastable sleptons and are characterized by fully reconstructible events. We outline many flavor measurements that are then possible and describe their prospects for resolving both the standard model and new physics flavor puzzles at the Large Hadron Collider.
73 citations
TL;DR: In this paper, the results of a series of noise and cross-talk tests on the SCT and TRT in their final assembled configuration, using final readout and supply hardware and software, are reported.
Abstract: The ATLAS (A Toroidal LHC ApparatuS) Inner Detector provides charged particle tracking in the centre of the ATLAS experiment at the Large Hadron Collider (LHC). The Inner Detector consists of three subdetectors: the Pixel Detector, the Semiconductor Tracker (SCT), and the Transition Radiation Tracker (TRT). This paper summarizes the tests that were carried out at the final stage of SCT+TRT integration prior to their installation in ATLAS. The combined operation and performance of the SCT and TRT barrel and endcap detectors was investigated through a series of noise tests, and by recording the tracks of cosmic rays. This was a crucial test of hardware and software of the combined tracker detector systems. The results of noise and cross-talk tests on the SCT and TRT in their final assembled configuration, using final readout and supply hardware and software, are reported. The reconstruction and analysis of the recorded cosmic tracks allowed testing of the offline analysis chain and verification of basic tracker performance parameters, such as efficiency and spatial resolution, in combined operation before installation.
49 citations
TL;DR: An easy-to-implement form of the Metropolis Algorithm is described which, unlike most standard techniques, is well suited to sampling from multi-modal distributions on spaces with moderate numbers of dimensions in environments typical of investigations into current constraints on Beyond-the-Standard-Model physics.
42 citations
TL;DR: In this article, the sensitivity of the CERN LHC to mass splitting was studied, which within minimal supergravity may be constrained down to Ω( √ O(10) √ √ 4 )$ for $30\text{ √ log n/n/n] of integrated luminosity.
Abstract: With sufficient data, CERN LHC experiments can constrain the smuon-selectron mass splitting through differences in the dielectron and dimuon edges from supersymmetry (SUSY) cascade decays. We study the sensitivity of the LHC to this mass splitting, which within minimal supergravity may be constrained down to $\mathcal{O}({10}^{\ensuremath{-}4})$ for $30\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity. Over substantial regions of SUSY breaking parameter space the fractional edge splitting can be significantly enhanced over the fractional mass splitting. Within models where the selectron and smuon are constrained to be universal at a high scale, edge splittings up to a few percent may be induced by renormalization group effects and may be significantly discriminated from zero. The edge splitting provides important information about high-scale SUSY breaking terms and should be included in any fit of LHC data to high-scale models.
40 citations
Posted Content•
TL;DR: A collection of studies on new physics at the LHC constitutes the report of the supersymmetry working group at the Workshop ''Physics at TeV Colliders'' as mentioned in this paper.
Abstract: This collection of studies on new physics at the LHC constitutes the report of the supersymmetry working group at the Workshop `Physics at TeV Colliders', Les Houches, France, 2007. They cover the wide spectrum of phenomenology in the LHC era, from alternative models and signatures to the extraction of relevant observables, the study of the MSSM parameter space and finally to the interplay of LHC observations with additional data expected on a similar time scale. The special feature of this collection is that while not each of the studies is explicitely performed together by theoretical and experimental LHC physicists, all of them were inspired by and discussed in this particular environment.
33 citations
University of Oxford1, University of Cambridge2, CERN3, Spanish National Research Council4, Queen Mary University of London5, University of Wisconsin-Madison6, University of Geneva7, University of Liverpool8, Rutherford Appleton Laboratory9, University of Birmingham10, Santa Cruz Institute for Particle Physics11, University of Sheffield12, University of Melbourne13
TL;DR: The SemiConductor Tracker data acquisition system will calibrate, configure, and control the approximately six million front-end channels of the ATLAS silicon strip detector, and its operation in calibration and data-taking modes is discussed.
Abstract: The SemiConductor Tracker (SCT) data acquisition (DAQ) system will calibrate, configure, and control the approximately six million front-end channels of the ATLAS silicon strip detector. It will provide a synchronized bunch-crossing clock to the front-end modules, communicate first-level triggers to the front-end chips, and transfer information about hit strips to the ATLAS high-level trigger system. The system has been used extensively for calibration and quality assurance during SCT barrel and endcap assembly and for performance confirmation tests after transport of the barrels and endcaps to CERN. Operating in data-taking mode, the DAQ has recorded nearly twenty million synchronously-triggered events during commissioning tests including almost a million cosmic ray triggered events. In this paper we describe the components of the data acquisition system, discuss its operation in calibration and data-taking modes and present some detector performance results from these tests
30 citations
A. Abdesselam1, Phillip Allport2, Christos Anastopoulos3, Britt Anderson4 +355 more•Institutions (36)
TL;DR: The emphasis of this paper is directed at the aspects of engineering design that turned a concept into a fully-functioning detector, as well as the integration and testing of large sub-sections of the final SCT barrel detector.
Abstract: The ATLAS SemiConductor Tracker (SCT) was built in three sections: a barrel and two end-caps. This paper describes the design, construction and final integration of the barrel section. The barrel is constructed around four nested cylinders that provide a stable and accurate support structure for the 2112 silicon modules and their associated services. The emphasis of this paper is directed at the aspects of engineering design that turned a concept into a fully-functioning detector, as well as the integration and testing of large sub-sections of the final SCT barrel detector. The paper follows the chronology of the construction. The main steps of the assembly are described with the results of intermediate tests. The barrel service components were developed and fabricated in parallel so that a flow of detector modules, cooling loops, opto-harnesses and Frequency-Scanning-Interferometry (FSI) alignment structures could be assembled onto the four cylinders. Once finished, each cylinder was conveyed to the next site for the mounting of modules to form a complete single barrel. Extensive electrical and thermal function tests were carried out on the completed single barrels. In the next stage, the four single barrels and thermal enclosures were combined into the complete SCT barrel detector so that it could be integrated with the Transition Radiation Tracker (TRT) barrel to form the central part of the ATLAS inner detector. Finally, the completed SCT barrel was tested together with the TRT barrel in noise tests and using cosmic rays.
26 citations
TL;DR: The SemiConductor Tracker (SCT) as mentioned in this paper is a silicon-strip tracking detector which forms part of the ATLAS inner detector and is designed to track charged particles produced in proton-proton collisions at the Large Hadron Collider (LHC) at CERN at an energy of 14 TeV.
Abstract: The ATLAS SemiConductor Tracker (SCT) is a silicon-strip tracking detector which forms part of the ATLAS inner detector. The SCT is designed to track charged particles produced in proton-proton collisions at the Large Hadron Collider (LHC) at CERN at an energy of 14 TeV. The tracker is made up of a central barrel and two identical end-caps. The barrel contains 2112 silicon modules, while each end-cap contains 988 modules. The overall tracking performance depends not only on the intrinsic measurement precision of the modules but also on the characteristics of the whole assembly, in particular, the stability and the total material budget. This paper describes the engineering design and construction of the SCT end-caps, which are required to support mechanically the silicon modules, supply services to them and provide a suitable environment within the inner detector. Critical engineering choices are highlighted and innovative solutions are presented – these will be of interest to other builders of large-scale tracking detectors. The SCT end-caps will be fully connected at the start of 2008. Further commissioning will continue, to be ready for proton-proton collision data in 2008.
14 citations
Academia Sinica1, Stony Brook University2, University of Milan3, University of Melbourne4, Science and Technology Facilities Council5, University of Oxford6, University of Genoa7, University of Manchester8, Spanish National Research Council9, Charles University in Prague10, University of Udine11, DSM12, Santa Cruz Institute for Particle Physics13, University of Geneva14, CERN15, Centre national de la recherche scientifique16, University of Sheffield17, University College London18, Lawrence Berkeley National Laboratory19, University of Copenhagen20, Ohio State University21, Russian Academy of Sciences22, University of Cambridge23, Max Planck Society24, University of Bonn25, University of Tsukuba26, Hampton University27, Radboud University Nijmegen28, University of Mannheim29, University of Bergen30, AGH University of Science and Technology31, Joint Institute for Nuclear Research32, Brookhaven National Laboratory33, SIM University34, University of Glasgow35, Iowa State University36, National Research Nuclear University MEPhI37
TL;DR: In this paper, a small set of final prototypes of the ATLAS Inner Detector silicon tracking system (Pixel Detector and SemiConductor Tracker) were used to take data during the 2004 Combined Test Beam.
Abstract: A small set of final prototypes of the ATLAS Inner Detector silicon tracking system (Pixel Detector and SemiConductor Tracker), were used to take data during the 2004 Combined Test Beam. Data were collected from runs with beams of different flavour (electrons, pions, muons and photons) with a momentum range of 2 to 180 GeV/c. Four independent methods were used to align the silicon modules. The corrections obtained were validated using the known momenta of the beam particles and were shown to yield consistent results among the different alignment approaches. From the residual distributions, it is concluded that the precision attained in the alignment of the silicon modules is of the order of 5 μm in their most precise coordinate.
TL;DR: In this paper, a small set of final prototypes of the ATLAS Inner Detector silicon tracker (Pixel and SCT) were used to take data during the 2004 Combined Test Beam.
Abstract: A small set of final prototypes of the ATLAS Inner Detector silicon tracker (Pixel and SCT) were used to take data during the 2004 Combined Test Beam. Data were collected from runs with beams of different flavour (electrons, pions, muons and photons) with a momentum range of 2 to 180 GeV/c. Four independent methods were used to align the silicon modules. The corrections obtained were validated using the known momenta of the beam particles and were shown to yield consistent results among the different alignment approaches. From the residual distributions, it is concluded that the precision attained in the alignment of the silicon modules is of the order of 5 micrometers in their most precise coordinate.