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| Home > Publications database > Development of a Triple GEM Readout Module for a Time Projection Chamber & Measurement Accuracies of Hadronic Higgs Branching Fractions in $\nu\nu$H at a 350 GeV ILC |
| Home > Publications database > Development of a Triple GEM Readout Module for a Time Projection Chamber & Measurement Accuracies of Hadronic Higgs Branching Fractions in $\nu\nu$H at a 350 GeV ILC |
| Book/Report/Dissertation / PhD Thesis | PUBDB-2016-02659 |
; ;
2016
Verlag Deutsches Elektronen-Synchrotron
Hamburg
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Please use a persistent id in citations: doi:10.3204/PUBDB-2016-02659
Report No.: DESY-THESIS-2016-018
Abstract: The presented thesis addresses the development and evaluation of one of the detector conceptfor the International Linear Collider (ILC). The ILC is a planned, future electron-positronlinear collider with a center-of-mass energy of up to 500 GeV in its first construction stage.The ILC is designed to perform precision measurements of the Standard Model, especially amodel-independent reconstruction of the electroweak symmetry breaking sector. In 2012, thediscovery of the Higgs boson at the LHC was an important first step and facilitates precisionmeasurements of the Higgs boson coupling constants at the ILC. Challenging design goals havebeen defined for the ILC detectors in order to reach the desired measurement precisions.One of the two ILC detector concepts is the International Large Detector (ILD). A large TimeProjection Chamber (TPC) is foreseen as the central tracking detector. In contrast to modernsilicon tracking detectors, a TPC provides a large number of space points, and thus continuoussampling of the track parameters. Therefore, TPCs offer great pattern recognition capabilitiesincluding the identification of particle decays within the sensitive volume. The design momentumresolution of the ILD TPC is $\sim(1=p_t) \approx 10^{-4}$ GeV$^{-1}$ which can be translated into atransverse spatial resolution of $\sigma_{r\phi} \le 100$ \mu m over the complete drift distance of 2.35 m.In the first part of the thesis, the development of a readout module for the TPC is presentedwhich fulfills the performance requirements of the ILD TPC. The developed readout moduleis based on a stack of three “Gas Electron Multiplier” (GEM) foils and a pad readout. Thinceramic grids are used as the support structure and spacers between the GEMs. The readoutmodule was tested in a prototype TPC with a maximal drift distance of around 60 cm at theDESY II test beam. An additional guard ring at the upper edge of the module was introducedto minimize field distortions at the module boundary. The presented data analysis is focusedon the impact of the field distortions and the spatial point resolution. An extrapolation ofthe measured spatial resolution to the ILD TPC working parameters shows that the desiredtransverse point resolution of $\sigma_{r\phi} \le 100$ \mu m can be accomplished.The coupling constants of the Higgs boson to other particles can be derived from a measurementof the Higgs decay branching ratios. These measurements are an important testof the Higgs sector as well as electroweak symmetry breaking. Even small deviations of themeasurements from the Standard Model predictions can indicate new physics. A high accuracyis essential to distinguish between a Standard-Model-like Higgs boson or different extensionsof the Standard Model. In the second part of the thesis, the achievable statistical measurementuncertainties of the Higgs branching ratios into b, c and g are studied in the final state$\nu\nu$H at a 350 GeV ILC. The study is based on a detailed detector simulation which includeslow momentum hadron background from photoproduction. Two different analysis proceduresare presented: an event counting method and three-dimensional template fits. Relative measurementprecisions of 1 %, 4.2 % and 10 % for $\sigma \times BR$ of b, g and c can be achievedfor an integrated luminosity of 330 fb$^{-1}$ and a beam polarization of $P_{e^{-},e^{+}} = (-0.8, +0.3)$.Additionally, the analysis is modified to distinguish between the two production processes: Higgs strahlung and WW fusion. Under the assumption that the Higgs-strahlung cross section is known precisely, the WW-fusion cross section can be determined to a relative precision of 2.7 %.
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