Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session R13: LHC I |
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Sponsoring Units: DPF Chair: Vasken Hagopian, Florida State University Room: Hyatt Regency Jacksonville Riverfront City Terrace 9 |
Monday, April 16, 2007 10:45AM - 10:57AM |
R13.00001: Electromagnetic Calorimeter Intercalibration with Neural Networks for the CMS Experiment at CERN Sergei Gleyzer The Electromagnetic Calorimeter (ECAL) of the Compact Muon Solenoid (CMS) detector is made of $\sim $76000 lead tungstate (PbWO$_{4})$ crystals. The calorimeter has excellent energy resolution and the small crystal size gives very good position resolution. During the summer of 2006 a production ECAL module was tested jointly with the Hadron Calorimeter in the CERN test beam in the energy range of a few GeV to 300GeV for pions and up to 150GeV for electrons. Given the large number of crystals intercalibration of ECAL is a very important and complicated task. I will discuss different approaches to intercalibration of ECAL including the method of using neural networks. [Preview Abstract] |
Monday, April 16, 2007 10:57AM - 11:09AM |
R13.00002: Calibration of the CMS Barrel Electromagnetic Calorimeter Using Neutral Pion Decays Marat Gataullin A rapid and precise calibration of the CMS electromagnetic calorimeter must be performed in situ at the LHC in order to fully exploit the physics reach of the CMS experiment. Achieving the design-goal calibration precision of 0.5\% will be particularly important for a discovery of the Higgs boson in the two-photon decay channel. In this paper we evaluate the potential of a novel calibration technique that makes use of photon pairs produced in neutral pion decays, $\pi^0 \rightarrow \gamma \gamma$. Such photon pairs will be selected using an online filter farm from the QCD events accepted by the Level 1 triggers. Assuming a Level~1 trigger rate of 10~kHz, the rate of suitable neutral pions is found to be as high as 1~kHz. We show that 95\% of the barrel electromagnetic calorimeter can be calibrated to at least a 1\% (0.5\%) precision after several days (weeks) of data-taking in the low-luminosity scenario of LHC, $L = 2 \cdot 10^{33} \, \mathrm{cm}^{-2}\,\mathrm{s}^{-1}$. The challenges of rapid data transfer and analysis on the filter farm are also discussed. [Preview Abstract] |
Monday, April 16, 2007 11:09AM - 11:21AM |
R13.00003: Electron/photon reconstruction in ATLAS Julia Hoffman The ATLAS experiment at the LHC will face the challenge of effective selection of interesting events in pp collisions at 14 TeV center-of-mass energy and rejection of an enormous QCD background. Efficient reconstruction of electrons and photons is one of the key issues in this challenge and will be important at the start of data-taking with ATLAS in 2007. In this talk an overview of current physics and system performance of the offline selection for electrons and photons is given. The results presented here are based on detailed Monte Carlo simulations. The electromagnetic calorimeter cluster algorithm and energy measurement will be described. In addition we will describe the electron identification based on the shower shape in the calorimeter and tracking information to achieve the required rejection of 10**5 against QCD jets. For photon identification, in addition to the shower shape in the calorimeter, recovery of photon conversions is an essential ingredient given the large amount of material in the inner tracker and this also relies heavily on the tracker performance. The electron and photon identification methods (cuts and multivariate analyses) and their performance will be discussed as a final step. [Preview Abstract] |
Monday, April 16, 2007 11:21AM - 11:33AM |
R13.00004: Alignment of the Silicon Detectors of the ATLAS Experiment Florian Heinemann The ATLAS Experiment is one of the four large detectors located at the Large Hadron Collider at CERN in Geneva, Switzerland. Data taking of ATLAS is expected to start in autumn 2007. The reconstruction of charged particle tracks is performed by silicon and drift tube based sub-detectors. In order to achieve the ATLAS physics goals the intrinsic resolution of the precision tracking devices should not be degenerated by more than 20{\%} due to misalignment. Thus, the positions of the silicon detector elements have to be known to an accuracy of about 10 micrometers. This precision can be achieved by track based alignment algorithms combined with measurements from hardware based alignment techniques. The alignment strategy and the proposed alignment algorithms for the ATLAS Inner Detector as well as their implementations into the common ATLAS software framework are presented. Results from a test-beam setup, from cosmic ray data as well as from full detector simulation studies are shown and discussed. [Preview Abstract] |
Monday, April 16, 2007 11:33AM - 11:45AM |
R13.00005: Analyses of the CMS ECAL+HCAL Test Beam Data and Jet Reconstruction Kazim Gumus, Heejong Kim, Lisa Berntzon, Nural Akchurin, Sung-Won Lee, Richard Wigmans We present the combined response of the CMS calorimeters to a variety of particles in the momentum rage of 1 to 350 GeV/c.~ Based on these measurements, obtained in 2006 at CERN's H2 beam line, we reconstruct the overall jet response of these calorimeters and apply them to the first day physics analyses of the CMS experiment at the Large Hadron Collider (LHC) which is scheduled to start this year.~ We discuss in detail the response differences to different single particles, optimization of the energy resolution of the combined calorimeter systems and the expected jet response and energy resolution. [Preview Abstract] |
Monday, April 16, 2007 11:45AM - 11:57AM |
R13.00006: Prospects for measuring the Underlying Event and Minimum Bias at the LHC Khristian Kotov We present in proton-proton collisions prospects of the studies of ``minimum bias'' collisions and of the ``underlying event'' in hard collisions with the CMS detector at the LHC proton collider under constructions. The ``underlying event'' accompanies every hard 2-to-2 scattering process in proton collision and consists of proton remnants and initial and final state radiation. Events collected with a trigger that is not very restrictive are referred to as minimum bias events. We measure particle multiplicity and transverse momentum density in the ``transverse'' region of charged particle jet production and in the central region of Drell-Yan muon-pair production. These observables help to find parameters for phenomenological models of non-perturbative QCD implemented in many event generators. The LHC will reach new energy and luminosity frontiers and will offer a unique opportunity to study the ``underlying event'' and ``minimum bias'' collisions up to the TeV scale. The CDF and D0 groups at the Tevatron have made significant contribution to this study at lower energy scales. We compare our studies based on simulation to their results. [Preview Abstract] |
Monday, April 16, 2007 11:57AM - 12:09PM |
R13.00007: Status and Design of Muon Reconstruction at the Large Hadron Collider with the CMS detector Adam Everett, Norbert Neumeister, Chang Liu The Compact Muon Solenoid (CMS) is a general purpose detector with a design goal to ensure efficient and accurate identification and reconstruction of muons. The CMS detector thus has a sophisticated muon system made up of tracking chambers and dedicated trigger chambers. The global muon reconstruction algorithms combine muons reconstructed in the three types of dedicated muon detector components with tracks reconstructed in the silicon tracker. The muon reconstruction software employs a modular design which allows muon reconstruction offline with the full calibration and detector readout. The modular design also allows muon reconstruction to be used in online event selection (HLT). We present and discuss the design, implementation, and performance, obtained on simulated data, of the CMS muon reconstruction and identification software. [Preview Abstract] |
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