LCWS13 - International Workshop on Future Linear Colliders

ABSTRACTS

Number of abstracts: 18 (17 submitted, 2 sent to CALICE for submission)

Physics & Detectors Plenary

CLICdp

• Speaker: André Sailer (CERN)

RD 1: Higgs Physics / Electroweak Symmetry Breaking

Measurement of the Higgs boson decays to gamma gamma and to Z gamma at a CLIC collider operating at 1.4 TeV

• Author(s): Christian Grefe (CERN), Eva Sicking (CERN)
• (Proposed) Speaker: Eva Sicking (CERN)
• Status: submitted 13-Oct-2013
• Abstract:
  The studies presented in this talk are part of an ongoing effort to investigate the complete physics potential of a CLIC collider operated at various energies for measurements of the SM Higgs boson properties. The prospects of the measurement of the cross section times branching ratio of the loop induced rare decays H -> Z gamma and H -> gamma gamma at a center-of-mass energy of 1.4 TeV are discussed. Both analyses are based on full detector simulations using Geant4. All relevant standard model backgrounds are considered. Beam-induced backgrounds from gamma gamma -> hadrons interactions are overlaid to the physics events.

Measurement of the top Yukawa coupling at a 1.4 TeV CLIC collider

• Author(s): Sophie Redford (CERN), Philipp Roloff (CERN), Marcelo Vogel (University of Santiago)
• (Proposed) Speaker: Marcelo Vogel (University of Santiago)
• Status: submitted 13-Oct-2013
• Abstract:
  The physics potential for a direct measurement of the top Yukawa coupling using the process e+e- -> ttH at a CLIC collider operated at 1.4 TeV is investigated. Final states with six and eight jets are reconstructed. This study addresses various aspects of the detector performance: jet clustering in complex hadronic final states, missing energy reconstruction, flavour-tagging and the identification of high-energy leptons. The analysis is based on a full detector simulation using Geant4. Beam-induced backgrounds from gamma gamma -> hadrons interactions are overlaid to the physics events.

H->WW* at 1.4 TeV and HZ->Hqq at 350 GeV

• Author(s): Mark Thomson (University of Cambridge)
• (Proposed) Speaker: Mark Thomson (University of Cambridge)
• Status: submitted 13-Oct-2013
• Abstract:
  A high-energy electron-positron collider like CLIC operating over a range of centre-of-mass energies would enable precise measurements of the properties of the Higgs boson to be made in a number of Higgs production and decay processes. This talk will describe the measurement potential at a centre-of-mass energy of 350 GeV for both invisible Higgs decays and the nearly model independent measurement of the HZ production cross-section using Z->qq decays. At higher energies, where the dominant Higgs production process is WW fusion, high statistics samples of Higgs boson decays can be accumulated. In this talk, the physics potential for measuring the H->WW* cross section at 1.4 TeV is reviewed.

SM-like Higgs decay into two muons at 1.4 TeV CLIC

• Author(s): Ivanka Bozovic-Jelisavcic (University of Belgrade)
• (Proposed) Speaker: Ivanka Bozovic-Jelisavcic (University of Belgrade)
• Status: submitted 13-Oct-2013
• Abstract:
  Branching fraction measurement of the SM-like Higgs boson decay into two muons will be reviewed in this talk at 1.4 TeV CLIC. The study is performed in the fully simulated ILD detector concept for CLIC, taking into consideration all the relevant physics and the beam-induced backgrounds, as well as the instrumentation of the very forward region to tag the high-energy electrons. Higgs couplings are known to be sensitive to BSM physics and we prove that BR times the Higgs production cross section can be measured with the 29% statistical accuracy in four years of the CLIC operation at 1.4 TeV center of mass energy. The study complements the Higgs physics program at energy stages foreseen at CLIC.

Higgs production in ZZ fusion at 1.4TeV

• Author(s): Aidan Robson (University of Glasgow)
• (Proposed) Speaker: Aidan Robson (University of Glasgow)
• Status: submitted 13-Oct-2013
• Abstract:
  We present a new study of Higgs production through ZZ fusion in e+e- collisions at 1.4TeV, using full simulation of the CLIC-ILD detector. ZZ fusion is the sub-leading Higgs production mechanism at sqrt(s)=1.4TeV, and we estimate the sensitivity to Higgs couplings that could be achieved by measuring this process.

Higgs Physics at CLIC

• Author(s): Philipp Roloff (CERN)
• (Proposed) Speaker: Philipp Roloff (CERN)
• Status: submitted 13-Oct-2013
• Abstract:
  A high-energy e+e- collider like CLIC would provide a clean environment to study the properties of the Higgs boson with very high precision. The physics performance for measurements of the Higgs properties is being studied using full detector simulations for a scenario where CLIC is constructed and operated in three energy stages. At an initial stage of CLIC operation at sqrt(s) = 350 GeV, the Higgsstrahlung process dominates. In the higher energy stages of CLIC operation (1.4 TeV and 3 TeV), large samples of Higgs bosons will be produced primarily through vector-boson fusion. In addition, various rare decays and production processes can be accessed at high energy. An overview of all possible measurements at the different energy stages is given in this talk. Results from different variants of combined fits to all the experimental measurements involving the Higgs boson couplings are presented.

Measurement of the trilinear Higgs self-coupling at 1.4 and 3 TeV CLIC

• Author(s): Tomas Lastovicka (Czech Academy of Sciences)
• (Proposed) Speaker: Tomas Lastovicka (Czech Academy of Sciences)
• Status: submitted 14-Oct-2013
• Abstract:
  An important test of the SM electroweak symmetry breaking sector is the measurement of the Higgs self-interactions. The measurement of the Higgs self-coupling strength provides a direct access to the Higgs potential, namely to the quartic potential coupling $\lambda$. We demonstrate that the large Higgs boson production cross section at a multi-TeV CLIC machine allows for a currently unchallenged measurement of the trilinear Higgs self-coupling at the 10% level. The results of the presented studies are based on detailed detector simulations, with full reconstruction of simulated events.

RD 2: Beyond Standard Model: SUSY, Cosmology

RD 3: Top Physics, QCD, Loopverein

Top Mass and Future Top Studies at CLIC

• Author(s): Frank Simon (MPI Munich)
• (Proposed) Speaker: Frank Simon (MPI Munich)
• Status: submitted 13-Oct-2013
• Abstract:
  Linear Colliders offer excellent possibilities for precise measurements of the mass of the top quark, in particular with a scan of the ttbar threshold. We present the results of full simulation studies, including a thorough investigation of systematic uncertainties due to the knowledge of the luminosity spectrum. The high energy of CLIC also provides the possibility to use the top quark as a tool to probe New Physics. An outlook on planned studies in this direction will also be presented.

RD 4: Gamma-Gamma

RD 5: Simulation, Detector Performance, Reconstruction

Clustering Algorithms for the Forward Calorimeters

• Author(s): André Sailer (CERN)
• (Proposed) Speaker: André Sailer (CERN), on behalf of the FCal Collaboration
• Status: approved by FCal 12-Oct-2013, submitted 13-Oct-2013
• Abstract:
  Clustering algorithms for the forward calorimeters LumiCal and BeamCal, of the linear collider detectors have been developed in the FCal collaboration. The clustering for the LumiCal focuses on precise reconstruction of electron and photon showers, and their separation. The clustering in the BeamCal aims for efficient tagging on top of the strong background from incoherent pairs. The existing implementations will be made available for the full reconstruction within the Marlin/LCIO framework soon. The current status and plans for the clustering algorithms for the forward calorimeters will be presented.

ILCDIRAC

• Author(s): Christian Grefe (CERN)
• (Proposed) Speaker: Christian Grefe (CERN)
• Status: submitted 18-Oct-2013
• Abstract:
  No abstract needed.

RD 6: Detector Integration, Machine-Detector Interface, Polarization

RD 7: Tracking, Vertexing

Physics performance studies for different CLIC vertex detector geometries

• Author(s): Philipp Roloff (CERN), Niloufar Alipour Tehrani (CERN and ETH Zurich)
• (Proposed) Speaker: Niloufar Alipour Tehrani (CERN and ETH Zurich)
• Status: submitted 13-Oct-2013
• Abstract:
  The impact of the detector geometry on the physics performance of the CLIC vertex detector is being investigated. Different options for the barrel detector and alternative layouts of the endcap regions fulfilling engineering requirements while minimizing the material budget are considered. This study is based on a full detector simulation using Geant4. The beauty and charm tagging performances for different jet energies and polar angles are the key observables used to compare the different investigated detector configurations.

Vertex-detector R&D for CLIC

• Author(s): Mathieu Benoit (CERN)
• (Proposed) Speaker: Mathieu Benoit (CERN)
• Status: submitted 13-Oct-2013
• Abstract:
  The requirements for the vertex detectors at the proposed Compact Linear Collider (CLIC) present an unprecedented combination of challenges in terms of material budget (0.2% X0 per layer, corresponding to 200 um of Si), spatial resolution (~3 um), time-tagging capability (~10 ns) and power dissipation (<50 mW/cm^2). A detector concept based on the hybrid planar pixel-detector technology is currently under development. It comprises fast, low-power and small-pitch readout ASICs (CLICpix) coupled to ultra-thin sensors via low-mass interconnects. In this talk we review the CLIC vertex-detector requirements and present the current status of the R&D on readout and sensors, Through-Silicon-Via (TSV) interconnects, powering and cooling solutions, and low-mass mechanical integration.

Calibration, Simulation and test-beam characterization for Timepix hybrid-pixel readout assemblies with ultra-thin sensors

• Author(s): Samir Arfaoui (CERN)
• (Proposed) Speaker: Samir Arfaoui (CERN)
• Status: submitted 13-Oct-2013
• Abstract:
  A vertex-detector concept based on the hybrid planar pixel-detector technology is currently under development for the proposed Compact Linear Collider (CLIC). The low material budget of only 0.2% X0 per layer corresponds to an equivalent thickness of 200 um of silicon and includes the infrastructure for powering and mechanical support. To reach this goal, sensors and readout ASICs will each have to be thinned down to approximately 50 um. In a first phase of R&D, hybrid readout assemblies with Timepix ASICs and ultra-thin sensors (50-200 um) have been produced and characterized with sources and in test-beam measurements. In this talk we present the current status of sensor calibration, test-beam analysis and comparison with simulations.

RD 8: Calorimetry, Muon Systems

Pandora PFA with SiW and ScW ECAL Models

• Author(s): John Marshall (University of Cambridge)
• (Proposed) Speaker: John Marshall (University of Cambridge)
• Status: submitted
• Abstract:
  Fine granularity particle flow calorimetry is the baseline for the detector at the ILC or CLIC. The Pandora algorithms provide the most sophisticated particle flow implementation and are used in the majority of detector-optimisation and physics-sensitivity studies. In this talk, the optimisation of the Electromagnetic Calorimeter (ECAL) will be discussed, and studies of jet energy resolutions will be presented for ECAL models instrumented with either silicon pixels or scintillator tiles. The need to ensure that the particle flow software is fully understood and optimised for each ECAL configuration will be emphasized throughout the talk.

Calibration of the W-DHCAL test beam data

• Author(s): Christian Grefe (CERN)
• (Proposed) Speaker: Christian Grefe (CERN)
• Status: sent to CALICE for approval, to be submitted via CALICE
• Abstract:
  The CALICE digital HCAL prototype using 54 RPC layers as active elements was tested at the CERN PS and SPS beam lines together with tungsten absorber plates, covering beam momenta from 1 GeV up to 300 GeV. We present the current status of the on-going data analysis and will discuss the quality of the data and the calibration procedure that is necessary to normalize the response of the different RPC modules.

Analysis of CALICE W-AHCAL data at 1 - 100 GeV

• Author(s): Eva Sicking (CERN)
• (Proposed) Speaker: Eva Sicking (CERN)
• Status: sent to CALICE for approval, to be submitted via CALICE
• Abstract:
  Results from the analysis of electron and hadron data with beam momenta from 1 to 100 GeV recorded at the CERN PS and SPS in 2010 and 2011 by the CALICE Scintillator-Tungsten HCAL will be presented. The detector response and the energy resolution will be discussed. The results are compared to Geant4 simulations.

Optical fiber calibration system and adaptive power supply

• Author(s): Jiri Kvasnicka (Institute of Physics FZU, Prague)
• (Proposed) Speaker: Jiri Kvasnicka (Institute of Physics FZU, Prague)
• Status: submitted 15-Oct-2013
• Abstract:
  In this talk we report on recent activities of Prague Institute of Physics group. It will address the fast LED driver with notched fiber light distribution system and an adaptive power supply for SiPMs, which has been recently developed.
  
  In the first part, the characteristics of the single-channel, quasi-resonant LED driver will be described. A 3mm near-UV LED (405nm wavelength) is used with the driver, which pushes a 1A half-sine current pulse through the LED. This current pulse is fully steerable and generates in the LED up to 600 nJ light flash with 3 ns optical pulse width. The light intensity capability is demonstrated by several tests with the analogue HCAL engineering prototype base unit (HBU), where the light from a single LED is distributed over the rows of 72 scintillator tiles. The light is guided through bundle of 3 notched fibers, which are machined for an equal light distribution to all scintillator tiles across the whole fiber length (spread <15%).
  
  In the second part, the technical aspects of the adaptive power supply prototype for the SiPM will be described. The power supply uses a precise temperature measurement for adjusting of the SiPM bias. As a result, the gain is kept constant during the temperature variations. The prototype allows trimming (by potentiometers) of the slope (dV/dT) and the voltage bias at a given temperature. It has been tested on some SiPMs in the climate chamber. Preliminary results show, that the gain can be stabilized within 1% deviation over the range of 5 to 40 degrees of Celsius.

Gain Stabilization of SiPMs

• Author(s): Gerald Eigen (University of Bergen)
• (Proposed) Speaker: Gerald Eigen (University of Bergen)
• Status: submitted 15-Oct-2013
• Abstract:
  The gain of SiPMs depends both on bias voltage and on temperature. For stable operations, both need to be kept constant. In an ILC calorimeter with millions of channels this is a challenging task. It is, therefore, desirable to compensate automatically for temperature variations by readjusting the bias voltage. We are designing an adaptive power supply to achieve this task. We anticipate a gain stability at the level of 1%. We present results of the first steps in this process, showing the gain dependence on bias voltage and temperature for several SiPMs from different manufacturers. We have built an adaptive power supply prototype and have performed first compensation studies.

-- Main.MichaelHauschild - 17-Sep-2013