LCWS11 - Linear Collider Workshop

ABSTRACTS

Repository for talks (to be uploaded for comments prior to the conference)

Number of abstracts: 18/21

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Higgs / Electroweak Symmetry Breaking

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Analyses of light Higgs decays for the CLIC CDR

• Authors: Tomas Lastovicka (Czech Academy of Sciences), Christian Grefe (CERN and University of Bonn), Jan Strube (CERN), Frederic Teubert (CERN), Blai Pie Valls (University of Barcelona)

• Speaker: Jan Strube (CERN)

• Status: submitted 1-Sep-2011

• Abstract:
  We present the measurements of the branching ratios of a light higgs boson at sqrt(s) = 3 TeV. These were carried out in the context of the CLIC CDR to study momentum resolution and flavour tagging performance especially in the forward region.

Study of Heavy Higgs Bosons in 3 TeV e+e- Collisions

• Authors: Marco Battaglia (University of California, Santa Cruz and CERN), Arnaud Ferrari (Uppsala University), Johan Relefors (Uppsala University), Sarah Zalusky (University of California, Santa Cruz)

• Speaker: Marco Battaglia (University of California, Santa Cruz and CERN)

• Status: submitted 1-Sep-2011, abstract sent 9-Sep-2011

• Abstract:
  The talk summarises requirements and results of the study of charged and neutral heavy Higgs boson pairs in 3 TeV collisions. After a discussion of the mass and width accuracy requirements in dark matter motivated MSSM scenarios, we present results obtained with fully simulated and reconstructed events and accounting for SM and machine-induced backgrounds for two different MSSM benchmark points.

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Beyond the SM: SUSY, Cosmology, Alternative

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CLIC Physics Potential

• Authors: James Wells (CERN)

• Speaker: James Wells (CERN)

• Status: submitted 1-Sep-2011, withdrawn 20-Sep-2011

• Abstract:
  This talk is a short summary of the work done for the "Physics Potential" chapter of the CLIC CDR. Topics addressed are prospects for discovery and careful study of Higgs bosons, supersymmetry, extra gauge forces, and other alternative scenarios of physics beyond the Standard Model.

Determination of Heavy Slepton Mass at CLIC

• Authors: Jean-Jacques Blaising (LAPP Annecy), Marco Battaglia (University of California, Santa Cruz and CERN)

• Speaker: Jean-Jacques Blaising (LAPP Annecy)

• Status: submitted 1-Sep-2011

• Abstract:
  The determination of scalar leptons and gauginos masses is an important part of the program of spectroscopic studies of Supersymmetry at a high energy linear collider. We present results of a study of selectron, smuon and sneutrino production in a Supersymmetric scenario at 3 TeV at CLIC. We report the expected accuracy on the production cross sections and on the selectron, smuon, sneutrino and gauginos mass determination. We discuss the performances on the lepton energy resolution and boson mass resolution, and the requirements on the luminosity spectrum, as well as on the detector time stamping capability. Results are obtained after full simulation and reconstruction with overlay of beam-beam induced background.

Mass and Cross Section Measurements of light-flavored Squarks at CLIC

• Authors: Frank Simon (MPI Munich), Lars Weuste (MPI Munich)

• Speaker: Frank Simon (MPI Munich)

• Status: submitted 1-Sep-2011

• Abstract:
  We present a study of the prospects for the measurement of TeV-scale light-flavored right-squark masses and and the production cross sections at a 3 TeV e+e− collider based on CLIC technology. The analysis is based on full Geant4 simulations of the CLIC_ILD detector concept, including standard model physics background and machine related hadronic background from two-photon processes. The events were reconstructed using particle flow event reconstruction, and the mass and cross sections were obtained from a template fit built from generator-level simulations with smearing to parametrize the detector response. Rejection of large cross-section physics background is based on multivariate techniques, and machine background is controlled through timing cuts in the reconstruction and through jet finding. For an integrated luminosity of 2 ab^-1, a statistical precision of 5.9 GeV, corresponding to 0.52% is obtained for unseparated first and second generation right squarks. For the combined cross section, a precision of 0.07 fb, corresponding to 5% is achieved.

Measurement of Chargino and Neutralino production at CLIC

• Authors: Tim Barklow (SLAC), Astrid Münnich (CERN), Philipp Roloff (CERN)

• Speaker: Philipp Roloff (CERN)

• Status: submitted 1-Sep-2011

• Abstract:
  We present a study performed for the CLIC CDR on the measurement of chargino and neutralino production at sqrt(s) = 3 TeV. Fully hadronic final states with four jets and missing transverse energy were considered. Results obtained using full detector simulation for the masses and for the production cross sections of the changino and the lightest and next-to-lightest neutralinos are discussed.

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Top / QCD / Loopverein

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Top mass measurement with the CLIC_ILD detector at 500 GeV

• Authors: Katja Seidel (MPI Munich), Frank Simon (MPI Munich)

• Speaker: Katja Seidel (MPI Munich)

• Status: submitted 1-Sep-2011

• Abstract:
  The top quark plays a special role in particle physics due to its high mass, which makes the top quark sensitive to new physics and measurements of electroweak symmetry breaking possible. It has sizable impact on the Higgs boson mass through radiative corrections, and, together with the W boson mass, drives electroweak predictions for the Higgs mass. Therefore an analysis to study the top mass and width was performed at a 500 GeV e+e- collider based on the CLIC technology. The analysis is based on full detector simulations of the CLIC_ILD detector concept using Geant4, including realistic background contributions from two photon processes. Event reconstruction is performed using a particle flow algorithm with stringent cuts to control the influence of background. The mass and width of top quarks is studied in fully-hadronic and semi-leptonic decays of ttbar pairs using event samples of signal and standard model background processes corresponding to an integrated luminosity of 100 fb^-1. The results will be compared to a similar analysis performed within the framework of the ILC.

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Simulation / Detector Performance / Reconstruction

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Lepton Identification at CLIC

• Authors: Jean-Jacques Blaising (LAPP Annecy), John Marshall (University of Cambridge), Jacopo Nardulli (CERN)

• Speaker: John Marshall (University of Cambridge)

• Status: submitted 1-Sep-2011

• Abstract:
  The efficient identification of high energy leptons is of crucial importance to analyses of potential beyond the standard model physics at CLIC. The identification takes place during the particle flow reconstruction and is performed by algorithms implemented in the PandoraPFA framework. This talk will describe the algorithms and discuss their performance.

Flavour tagging at CLIC

• Authors: Tomas Lastovicka (Czech Academy of Sciences), Katja Seidel (MPI Munich), Jan Strube (CERN)

• Speaker: Jan Strube (CERN)

• Status: submitted 1-Sep-2011

• Abstract:
  We present an overview over the Flavour Tagging studies for the benchmarking analyses in the CLIC CDR with an eye on the impact of CLIC backgrounds on the tagging performance.

Particle Flow Performance at CLIC

• Authors: John Marshall (University of Cambridge), Astrid Münnich (CERN), Mark Thomson (University of Cambridge)

• Speaker: Astrid Münnich (CERN)

• Status: submitted 1-Sep-2011

• Abstract:
  The particle flow approach (PFA) to calorimetry aims to reconstruct the four-vectors of all visible particles in an event. Charged particle momenta are measured in the tracking detectors and only energy measurements for photons and neutral hadrons are obtained from the calorimeters. The performance of PFA is studied for the two detector concepts under consideration for CLIC: CLIC_SID and CLIC_ILD. The influence of the machine induced background of gamma gamma -> hadrons events on the jet energy resolution is investigated.

Monte Carlo production for the CLIC CDR

• Authors: Akiya Miyamoto (KEK), Stephane Poss (CERN), Jan Strube (CERN)

• Speaker: Stephane Poss (CERN)

• Status: submitted 1-Sep-2011, abstract changed 18-Sep-2011

• Abstract:
  The CLIC conceptual design report required several dedicated physics studies to benchmark the detectors' concepts. To perform those studies, a large number of Monte Carlo events were needed at generator, simulation, and reconstruction levels. We present the production system used as well as the required resources. We emphasize on the generator step, that required the use of WHIZARD and PYTHIA, and we present the technical issues faced, in particular the handling of Overlay events. Finally, we show examples of functionalities that can be applied on the ILC DBD context.

Beam-Induced Backgrounds in the CLIC Detectors

• Authors: Dominik Dannheim (CERN), Andre Sailer (CERN and Humboldt University of Berlin), Mark Thomson (University of Cambridge)

• Speaker: Andre Sailer (CERN and Humboldt University of Berlin)

• Status: submitted 1-Sep-2011, to be moved to Detector Integration / MDI / Polarization session?

• Abstract:
  The beam parameters of the proposed CLIC concept for a linear electron-positron collider with a centre-of-mass energy of up to 3 TeV will lead to high rates of beam-induced background events in the tracking and forward regions of the detectors. Simulation studies of two-photon and incoherent interactions are presented. The CLIC detector models and their optimisation to reduce background occupancies are described. The characteristics of the events are discussed and resulting occupancies and energy deposits, as well as expected levels of both total ionising dose and displacement damage in the detectors are discussed.

Machine background suppression at CLIC

• Authors: Philipp Roloff (CERN), Katja Seidel (MPI Munich), Mark Thomson (University of Cambridge)

• Speaker: Katja Seidel (MPI Munich)

• Status: submitted 1-Sep-2011, to be moved to Detector Integration / MDI / Polarization session?

• Abstract:
  At CLIC hadronic background from two-photon processes, due the high bunch crossing frequency of 2 GHz, the high beamstrahlung due to the high collision energy and strong beam focusing, will lead to a significant pile-up in the detectors. This gamma gamma -> hadrons background is a severe challenge for event reconstruction and physics analysis. We will discuss the influence of this background, and strategies for its mitigation by combinations of timing and momentum cuts in the reconstruction and by specific jet-finding algorithms.

Muon background mitigation and impact on the detector

• Authors: Mark Thomson (University of Cambridge)

• Speaker: Mark Thomson (University of Cambridge)

• Status: submitted 1-Sep-2011, to be moved to Detector Integration / MDI / Polarization session?

• Abstract:
  Due to the 0.5 ns bunch structure at CLIC, inevitably a detector at CLIC will integrate over multiple bunch crossings. As a consequence, high energy beam halo muons from multiple bunch crossings are a potentially significant source of background. In this talk the impact of the beam halo muon background on the calorimeters at CLIC will be discussed. It will be shown that the effects can be mitigated utilising the high granularity readout of the calorimeters and dedicated pattern recognition algorithms.

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Detector Integration / MDI / Polarization

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Update on CLIC detector magnets and R&D

• Authors: Andrea Gaddi (CERN)

• Speaker: Andrea Gaddi (CERN)

• Status: submitted 1-Sep-2011

• Abstract:
  to be delivered

Passive Isolation R&D

• Authors: Fernando Duarte Ramos (CERN), Hubert Gerwig (CERN)

• Speaker: Fernando Duarte Ramos (CERN)

• Status: submitted 1-Sep-2011, abstract sent 5-Sep-2011

• Abstract:
  The design parameters of CLIC require that the final focusing quadrupoles (in particular QD0, but also QF1) be stabilized to the sub-nanometer level in the vertical direction, at frequencies higher than about 4 Hz. Although work is underway in the field of the active mechanical stabilization of QD0, every effort should be made in order to provide a “stable ground” as a basis for the active stabilization. This implies the choice of a “quiet” site, the reduction as far as possible of noise from equipment, etc.. In addition, the introduction of a passive, heavy, low frequency pre-isolator placed between the ground and the final focusing quadrupoles might be of great importance. In this talk, the theoretical principles behind the chosen approach, together with results from both ANSYS simulations of the proposed design and an experimental test set-up are presented.

Detector movements on platforms and infrastructure

• Authors: Hubert Gerwig (CERN), Maciej Herdzina (CERN)

• Speaker: Maciej Herdzina (CERN)

• Status: submitted 1-Sep-2011

• Abstract:
  to be delivered

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Tracking / Vertex

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Background Studies for Vertex and Forward Tracking Optimisation

• Authors: Dominik Dannheim (CERN), Juan Trenado (University of Barcelona), Marcel Vos (University of Valencia)

• Speaker: Juan Trenado (University of Barcelona)

• Status: submitted 1-Sep-2011, abstract sent 9-Sep-2011

• Abstract:
  Previous simulations of background radiation in ILC Vertex and Tracking region configuration, with a centre-of-mass energy of up to 3 TeV, showed the need to redesign these for the CLIC requirements. Layout studies were performed to find and optimal configuration for Vertex and Tracking region. Using the new configuration, detailed studies of the background radiation for different technologies were carried out. We present a new layout for Vertex and Tracking region, and the background radiation impact in the behaviour of the Forward Tracking, depending the technology used.

CLIC Vertex Detector Mechanics

• Authors: Bill Cooper (FNAL)

• Speaker: Bill Cooper (FNAL)

• Status: submitted 1-Sep-2011

• Abstract:
  Geometry, mechanical support, cooling, and other mechanical aspects of a vertex detector based upon CLIC design parameters will be described. Pixel sensors, a barrel and disk geometry, low-mass support structures, and air cooling are assumed. Options for sensor support, power delivery, and external vertex detector support will be described.

Tracking performance in CLIC_ILD and CLIC_SiD

• Authors: Christian Grefe (CERN and University of Bonn), Michael Hauschild (CERN), Martin Killenberg (CERN), Jacopo Nardulli (CERN)

• Speaker: Michael Hauschild (CERN)

• Status: submitted 1-Sep-2011

• Abstract:
  The tracking performance of the TPC-based CLIC_ILD tracking system and of the All-Silicon CLIC_SiD tracking system will be presented. Tracking efficiencies, fraction of badly reconstructed tracks and momentum resolution have been studied. The addition of background from gamma gamma -> hadrons of 3.2 events per bunch crossing does not significantly change the results. The goal of a momentum resolution of sigma(1/p_t) = 2 x 10^-5 GeV^-1 is reached for tracks with p_t > 100 GeV in di-jet and in ttbar events with large track density. For the CLIC_ILD tracking system, the capability of time stamping of tracks has been investigated. 90% of the tracks could be correctly reconstructed to within +/- 5 bunch crossings.

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Calorimetry / Muons

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Test beams (hardware), detector calibration plots (light yield, noise above threshold, MIPs calibration, etc) (exact title + abstract to be added)

• Authors: Shaojun Lu (DESY), Angela Lucaci-Timoce (CERN), Martin Killenberg (CERN),

• Speaker: Shaojun Lu (DESY)

• Status: to be approved and submitted through CALICE

• Abstract:
  to be delivered

CALICE T3B: Measurements of the Time Structure of Hadronic Showers in a Scintillator-Tungsten HCAL

• Authors: Frank Simon (MPI Munich), Christian Soldner (MPI Munich), Lars Weuste (MPI Munich)

• Speaker: Frank Simon (MPI Munich)

• Status: to be approved and submitted through CALICE

• Abstract:
  For calorimeter applications requiring precise time stamping, the time structure of hadronic showers in the detector is a crucial issue. This applies in particular to detector concepts for CLIC, where a hadronic calorimeter with tungsten absorbers is being considered to achieve a high level of shower containment while satisfying strict space constraints. The high hadronic background from gamma gamma to hadron processes at CLIC, together with the bunch crossing frequency of 2 GHz requires good time stamping in the detectors.

  To provide first measurements of the time structure in a highly granular scintillator-tungsten calorimeter, T3B, a dedicated timing experiment, was installed behind the last layer of the CALICE WHCAL prototype, a 30 layer tungsten scintillator calorimeter. T3B consists of 15 small scintillator cells with silicon photomultiplier, read out with fast digitizers over 2.4 us, and provides detailed measurements of the time structure of the signal. The offline data reconstruction performs an automatic gain calibration using noise events recorded between physics triggers and allows the determination of the arrival time of each photon at the photon sensor.

  We will discuss the T3B setup, its calibration and data reconstruction, and will report first results of the time structure of the calorimeter response for 10 GeV pions recorded at the CERN PS, confronted with GEANT4 simulations using several physics lists.

-- Main.MichaelHauschild - 26-Mar-2011