Eldorado Collection:http://hdl.handle.net/2003/442024-03-29T05:32:34Z2024-03-29T05:32:34ZThe radiosensitizing effect of platinum nanoparticles in proton irradiations is not caused by an enhanced proton energy deposition at the macroscopic scaleBehrends, CarinaBäcker, Claus MaximilianSchilling, IsabelleZwiehoff, SandraWeingarten, JensKröninger, KevinRehbock, C.Barcikowski, StephanWulff, JörgBäumer, ChristianTimmermann, B.http://hdl.handle.net/2003/412452023-02-16T23:12:03Z2022-07-29T00:00:00ZTitle: The radiosensitizing effect of platinum nanoparticles in proton irradiations is not caused by an enhanced proton energy deposition at the macroscopic scale
Authors: Behrends, Carina; Bäcker, Claus Maximilian; Schilling, Isabelle; Zwiehoff, Sandra; Weingarten, Jens; Kröninger, Kevin; Rehbock, C.; Barcikowski, Stephan; Wulff, Jörg; Bäumer, Christian; Timmermann, B.
Abstract: Objective. Due to the radiosensitizing effect of biocompatible noble metal nanoparticles (NPs), their administration is considered to potentially increase tumor control in radiotherapy. The underlying physical, chemical and biological mechanisms of the NPs' radiosensitivity especially when interacting with proton radiation is not conclusive. In the following work, the energy deposition of protons in matter containing platinum nanoparticles (PtNPs) is experimentally investigated. Approach. Surfactant-free monomodal PtNPs with a mean diameter of (40 ± 10) nm and a concentration of 300 μg ml−1, demonstrably leading to a substantial production of reactive oxygen species (ROS), were homogeneously dispersed into cubic gelatin samples serving as tissue-like phantoms. Gelatin samples without PtNPs were used as control. The samples' dimensions and contrast of the PtNPs were verified in a clinical computed tomography scanner. Fields from a clinical proton machine were used for depth dose and stopping power measurements downstream of both samples types. These experiments were performed with a variety of detectors at a pencil beam scanning beam line as well as a passive beam line with proton energies from about 56–200 MeV. Main results. The samples' water equivalent ratios in terms of proton stopping as well as the mean proton energy deposition downstream of the samples with ROS-producing PtNPs compared to the samples without PtNPs showed no differences within the experimental uncertainties of about 2%. Significance. This study serves as experimental proof that the radiosensitizing effect of biocompatible PtNPs is not due to a macroscopically increased proton energy deposition, but is more likely caused by a catalytic effect of the PtNPs. Thus, these experiments provide a contribution to the highly discussed radiobiological question of the proton therapy efficiency with noble metal NPs and facilitate initial evidence that the dose calculation in treatment planning is straightforward and not affected by the presence of sensitizing PtNPs.2022-07-29T00:00:00ZCharacterisation of irradiated and non-irradiated silicon sensors with a table-top two photon absorption TCT systemPape, SebastianFernández García, M.Moll, M.Montero, R.Palomo, F.R.Vila, I.Wiehe, M.http://hdl.handle.net/2003/412432023-02-16T23:12:05Z2022-08-16T00:00:00ZTitle: Characterisation of irradiated and non-irradiated silicon sensors with a table-top two photon absorption TCT system
Authors: Pape, Sebastian; Fernández García, M.; Moll, M.; Montero, R.; Palomo, F.R.; Vila, I.; Wiehe, M.
Abstract: A tabletop Two Photon Absorption-Transient Current Technique (TPA-TCT) set-up built at CERN was used to investigate a non-irradiated PIN diode, an irradiated PIN diode, and a non-irradiated 5 × 5-multipad HPK LGAD. The intrinsic three dimensional spatial resolution of this method is demonstrated under normal incidence of the laser probe. A charge collection versus depth profile of the non-irradiated PIN diode is presented, where reflection on the rear silicon-air interface was observed. It is found that the time-over-threshold versus depth profile is particularly suitable to determine the boundaries of the DUT's active volume. A depth scan of the irradiated PIN diode is discussed and a method to omit the single photon absorption background is presented. Finally, a charge collection measurement in the inter-pad region of the 5 × 5-multipad HPK LGAD is presented and it is demonstrated that TPA-TCT can be used to image the implantation and the electric field of segmented silicon devices in a three dimensional manner.2022-08-16T00:00:00ZWith bottom-up to the top and beyondSedlaczek, Kevinhttp://hdl.handle.net/2003/410652022-09-07T22:12:03Z2022-01-01T00:00:00ZTitle: With bottom-up to the top and beyond
Authors: Sedlaczek, Kevin
Abstract: In this thesis, the measurement of the inclusive and differential production cross-sections of a top quark in association with an anti-top quark at large transverse momenta in proton-proton collisions, as well as one of the first direct interpretations of such a measurement in the framework of effective field theories (EFT) are presented. The measurement is based on data collected with the ATLAS detector at the Large Hadron Collider at CERN and corresponds to an integrated luminosity of 139 fb-1. Events of the process tt → WbWb→lvbqqb in the region of large transverse momenta are analyzed. After unfolding the data to particle level, the cross-section is presented as function of several kinematic variables relevant to this process. In order to validate the predictions based on the Standard Model of particle physics, the data is compared to several predictions and effects of higher order contributions in quantum chromodynamics are investigated. In this measurement, the impact of systematic uncertainties on the energy reconstruction of jets is reduced by employing a novel method. It introduces a scaling of the energies of the jets in order to decrease discrepancies in the reconstruction of jet energies in data and the different predictions. Using this precision measurement, an indirect and model-independent search for physics beyond the Standard Model (BSM) in the framework of EFT is performed.
In particular, the effects of two EFT operators on the coupling of the top quark to gluons and other quarks are investigated. A model based on the two operators OtG and O(8)tq in the top-quark sector of the EFT framework is employed to interpret the measurement in the context of BSM physics.
Bayesian statistics is used in order to set limits on the effects of these operators via their respective Wilson coefficients CtG and C(8)tq. This analysis is among the very first direct EFT interpretations of a differential cross-section measurement in the top-quark sector. The determined limits on C(8)tq are competitive with recent global combinations, while soundly treating all parameters of the interpretation and without employing any of the assumptions, typical in global combinations. Both Wilson coefficients are found to be compatible with the SM.; In dieser Arbeit wird die Messung der inklusiven und differentiellen Produktionswirkungsquerschnitte eines Top-Quarks in Verbindung mit einem Anti-Top-Quark bei großen Transversalimpulsen in Proton-Proton-Kollisionen vorgestellt. Des Weiteren wird eine der ersten direkten Interpretationen einer solchen Messung im Rahmen der effektiven Feldtheorien (EFT) vorgestellt. Die Messung basiert auf Daten, die mit dem ATLAS-Detektor am Large Hadron Collider am CERN aufgenommen wurden und einer integrierten Luminosität von 139 fb-1 entsprechen.
Es werden Ereignisse des Prozesses tt → WbWb→lvbqqb im Bereich großer Transversalimpulse analysiert. Nach der Entfaltung der Daten auf Teilchenebene wird der Wirkungsquerschnitt als Funktion mehrerer, für diesen Prozess relevanter, kinematischer Variablen untersucht. Um die Vorhersagen auf der Grundlage des Standardmodells der Teilchenphysik zu überprüfen, werden die Messungen mit verschiedenen Vorhersagen verglichen und die Auswirkungen von Korrekturen höherer Ordnung in der Quantenchromodynamik untersucht. Bei dieser Messung werden die Auswirkungen systematischer Unsicherheiten auf die Energierekonstruktion von Jets durch den Einsatz einer neuartigen Methode verringert. Dazu wird eine Skalierung der Energien der Jets eingeführt, um die Diskrepanzen bei der Rekonstruktion der Jet-Energien in den Daten und den verschiedenen Vorhersagen zu verringern. Mit dieser Präzisionsmessung wird eine indirekte und modellunabhängige Suche nach Physik jenseits des Standardmodells (BSM) im Rahmen der EFT durchgeführt. Insbesondere werden die Auswirkungen von zwei EFT-Operatoren auf die Kopplung des Top-Quarks an Gluonen und andere Quarks untersucht. Ein Modell, das auf den beiden Operatoren OtG und O(8)tq im Top-Quark-Sektor der EFT basiert, wird zur Interpretation der Messung im Kontext von Suchen nach BSM-Physik konstruiert und verwendet. Mit Hilfe der Bayes'schen Statistik werden die Auswirkungen dieser Operatoren über ihre jeweiligen Wilson-Koeffizienten CtG und C(8)tq begrenzt.
Diese Analyse ist eine der ersten direkten EFT-Interpretationen einer differentiellen Wirkungsquerschnittsmessung im Top-Quark-Sektor. Die ermittelten erlaubten Parameterbereiche für C(8)tq sind konkurrenzfähig mit den jüngsten globalen Kombinationen, wobei alle Parameter der Interpretation konsistent behandelt werden und keine der für globale Kombinationen typischen Annahmen getroffen werden. Beide Wilson-Koeffizienten erweisen sich als kompatibel mit dem SM.2022-01-01T00:00:00ZNuclear physics in proton therapy: new approaches for proton beam range verification using delayed gamma-raysBäcker, Claus Maximilianhttp://hdl.handle.net/2003/409222022-05-25T22:12:04Z2022-01-01T00:00:00ZTitle: Nuclear physics in proton therapy: new approaches for proton beam range verification using delayed gamma-rays
Authors: Bäcker, Claus Maximilian
Abstract: In-vivo monitoring of the delivered dose is desirable in radiation therapy. Radionuclides generated during the proton irradiation can be used for imaging methods from nuclear medicine after the treatment session. In order to improve these techniques, this work focuses on three different aspects of nuclear physics from basic nuclear physics measurements to a clinical validation. The most relevant nuclear interaction is the production of C-11 from carbon as this nuclear interaction is used as a monitor reaction for the measurement of several other radionuclides. Furthermore, this is one of the relevant residuals produced from the tissue nuclei. As the data from the literature scatter by about 15%, a new reference cross section value of (68 ± 3) mb at 97 MeV is determined from the cross sections measured in different settings. In a second part, the activation of iodine during proton irradiation is investigated. Several radionuclides are produced from iodine which decay by the emission of positrons and can potentially be used for PET imaging subsequent to the fractional treatment. In the last step, the activation of titanium implants is investigated. A benchmarking test including MC simulations is performed which study reveals the limited applicability of PET imaging with implants for field verification in proton therapy.; Die Überwachung der applizierten Dosisverteilung in der Strahlentherapie kann zur Optimierung der Therapie genutzt werden. Während der Protonenbestrahlung erzeugte Radionuklide können nach der Behandlungssitzung zur Bildgebung mit Methoden aus der Nuklearmedizin verwendet werden. Die vorliegende Arbeit untersucht drei verschiedene kernphysikalische Aspekte von der Untersuchung von Kernreaktionen hin zu einer klinischen Validierung, um diese Techniken zu verbessern. Zunächst wird die Produktion von C-11 aus Kohlenstoff untersucht, da diese Reaktion in der Kernphysik als Monitorreaktion verwendet wird. Die Literaturwerte der Wirkungsquerschnitte variieren um bis zu 15%. Außerdem stellt diese Reaktion eine wichtige Produktion von Radionukliden in menschlichem Gewebe dar. Als neuer Referenzwert kann (68 ± 3) mb bei einer Energie von 97 MeV bestimmt werden. In einem weiteren Schritt wird die Aktivierung von Iod untersucht. Da viele Positronenemitter bei der Bestrahlung von Iod produziert werden, kann die Aktivierung von Iod zur PET Bildgebung verwendet werden. Als letztes wird die Aktivierung von Titanimplantaten betrachtet. Dazu wird dazu ein Sensitivitätstest inklusive der Aktivitätsvorhersage durchgeführt, der die beschränkten Einsatzmöglichkeiten der PET Bildgebung zur Feldverifikation in der Protonentherapie aufzeigt.2022-01-01T00:00:00ZThe silicon strip detector of the ATLAS Inner Tracker: from individual sensing units to multi-module petal structuresRenardi, Alessiahttp://hdl.handle.net/2003/409062022-05-19T06:56:40Z2022-01-01T00:00:00ZTitle: The silicon strip detector of the ATLAS Inner Tracker: from individual sensing units to multi-module petal structures
Authors: Renardi, Alessia
Abstract: Nowadays particle detector technology is taking big steps forwards and new devices
dedicated to particle physics show very high performance. Particularly the semiconductor
detectors have advanced significantly and are used for tracking purposes
in the A Toroidal LHC ApparatuS (ATLAS) experiment at CERN thanks to their
excellent spacial resolution: the compact size of the silicon and its high granularity
allow to reach a precision measurement of few tens of microns.
This thesis is focused on the upgrade of the ATLAS tracking detector required for the
High Luminosity Large Hadron Collider (HL-LHC), starting in 2027. The HL-LHC
foresees an integrated luminosity of L = 3000 fb−1, which comes with an unprecedented
rate of proton collisions, with a pile-up of h i = 200, and very high radiation
doses. As the current inner detector has not been designed for the HL-LHC environmental
conditions, an all-silicon Inner Tracker (ITk) will take its place during
Phase-II upgrade of the ATLAS experiment.
The ITk strip endcap sub-detector is the main topic of this PhD project. The investigation
covers the assembly of silicon strip endcap modules and their loading on
a local support structure. The building and loading procedures are presented as well
as results of quality control (QC) tests carried out on prototyping components to
establish their working performance and the fulfillment of the specifications. This
work provides the procedure optimization in order to achieve the requirements imposed
by the collaboration.
Results on prototyping components, such as a fully electrical module and a semielectrical
petal, both built and tested at DESY, are presented. They are followed by
tests on an electrical petal performed at low temperature with the evaporative CO2
cooling technique. The QC tests carried out on all prototypes have demonstrated
that they have been properly assembled and are fully functional. Moreover they
fulfil the respective requirements validating therefore the components design and the
building methods.; In der heutigen Zeit macht die Detektortechnologie große Fortschritte, und neue
Geräte für die Teilchenphysik sind sehr leistungsstark. Insbesondere die Halbleiterdetektoren
haben sich erheblich weiterentwickelt und werden dank ihrer exzellenten
räumlichen Auflösung im A Toroidal LHC ApparatuS (ATLAS) Experiment am
CERN für die Spurrekonstruktion eingesetzt. Die dünnen Siliziumsensoren sowie die
hohe Granularität ermöglichen Präzisionsmessungen mit einer Auflösung von einigen
zehn Mikrometern.
Die vorliegende Arbeit befasst sich mit dem Upgrade des ATLAS-Spurdetektors,
das für den im Jahr 2027 in Betrieb gehenden High Luminosity Large Hadron Collider
(HL-LHC) erforderlich ist. Der HL-LHC sieht eine integrierte Luminosität von
L = 3000 fb−1 vor, was mit einer bisher unerreichten Rate von Protonkollisionen mit
einem Pile-up von h i = 200 und sehr hohen Strahlungsdosen einhergeht. Da der
derzeitige innere Spurdetektor nicht für die Umgebungsbedingungen des HL-LHC
ausgelegt ist, wird er während des Phase-II-Upgrades durch den neuen, vollständig
aus Siliziumsensoren bestehenden Inner Tracker (ITk) ersetzen werden.
Der ITk-Streifen-Endkappen-Subdetektor ist das Hauptthema dieses PhD-Projekts.
Es umfasst den Zusammenbau von Siliziumstreifen-Endkappenmodulen und deren
Montage auf einer lokalen Trägerstruktur. Es werden die Konstruktions- und Montageverfahren
sowie die Ergebnisse von Qualitätskontrolltests vorgestellt, die an Prototypkomponenten
durchgeführt wurden, um deren Funktionalität sowie die Erfüllung
der Spezifikationen sicherzustellen. Im Rahmen dieser Arbeit wurden die Verfahren
optimiert, um die von der Kollaboration gestellten Anforderungen zu erfüllen.
Es werden Ergebnisse zu Prototypkomponenten, wie beispielsweise einem vollständig
elektrischen Modul und einem halbelektrischen Petals vorgestellt, die beide bei DESY
gebaut und getestet wurden. Des Weiteren werden Tests an einem elektrischen Petal
vorgestellt, die bei niedrigen Temperaturen mit der CO2-Verdunstungskühltechnik
durchgeführt wurden. Die an allen Prototypen durchgeführten Qualitätskontrolltests
haben gezeigt, dass sie ordnungsgemäß zusammengebaut wurden und voll funktionsfähig
sind. Darüber hinaus erfüllen sie die entsprechenden Anforderungen, so
dass das Design der Komponenten und die Bauverfahren validiert wurden.2022-01-01T00:00:00ZExperimental consolidation and absolute measurement of the nat C(p,x)11 C nuclear activation cross section at 100 MeV for particle therapy physicsBäcker, Claus MaximilianHorst, FelixAdi, WihanBäumer, ChristianGerhardt, MarcelJentzen, WalterKazek, Sandra LauraKröninger, KevinSchuy, ChristophVerbeek, NicoWeingarten, JensWulff, JörgTimmermann, Beatehttp://hdl.handle.net/2003/408252022-03-23T23:12:04Z2021-08-02T00:00:00ZTitle: Experimental consolidation and absolute measurement of the nat C(p,x)11 C nuclear activation cross section at 100 MeV for particle therapy physics
Authors: Bäcker, Claus Maximilian; Horst, Felix; Adi, Wihan; Bäumer, Christian; Gerhardt, Marcel; Jentzen, Walter; Kazek, Sandra Laura; Kröninger, Kevin; Schuy, Christoph; Verbeek, Nico; Weingarten, Jens; Wulff, Jörg; Timmermann, Beate
Abstract: The natC(p,x)11C reaction has been discussed in detail in the past [EXFOR database, Otuka et al. (Nuclear Data Sheets 120:272–276, 2014)]. However, measured activation cross sections by independent experiments are up to 15% apart. The aim of this study is to investigate underlying reasons for these observed discrepancies between different experiments and to determine a new consensus reference cross section at 100 MeV. Therefore, the experimental methods described in the two recent publications [Horst et al. (Phys Med Biol https://doi.org/10.1088/1361-6560/ab4511 [Titel anhand dieser DOI in Citavi-Projekt übernehmen] , 2019) and Bäcker et al. (Nuclear Instrum Methods Phys Res B 454:50–55, 2019)] are compared in detail and all experimental parameters are investigated for their impact on the results. For this purpose, a series of new experiments is performed. With the results of the experiments a new reference cross section of (68±3) mb is derived at (97±3) MeV proton energy. This value combined with the reliably measured excitation function could provide accurate cross section values for the energy region of proton therapy. Because of the well-known gamma-ray spectrometer used and the well-defined beam characteristics of the treatment machine at the proton therapy center, the experimental uncertainties on the absolute cross section could be reduced to 3%. Additionally, this setup is compared to the in-beam measurement setup from the second study presented in the literature (Horst et al. 2019). Another independent validation of the measurements is performed with a PET scanner.2021-08-02T00:00:00ZDevelopment of tools for Bayesian data analysis and their application in the search for physics beyond the Standard ModelGrunwald, Corneliushttp://hdl.handle.net/2003/406392022-01-03T13:19:06Z2021-01-01T00:00:00ZTitle: Development of tools for Bayesian data analysis and their application in the search for physics beyond the Standard Model
Authors: Grunwald, Cornelius
Abstract: In this thesis, methods for Bayesian data analysis are employed in the search for physics beyond the Standard Model (BSM). A new implementation of the Bayesian Analysis Toolkit in
Julia (BAT.jl) is introduced as a modern data analysis framework providing algorithms for
Bayesian inference. The EFTfitter.jl package for interpreting measurements in the context of
effective field theories (EFTs) is presented. It facilitates combining measurements and estimating underlying parameters with Bayesian inference. Both tools are employed for indirect
BSM searches using EFTs. Wilson coefficients of dimension-six operators from the top-quark
sector of the Standard Model effective field theory (SMEFT) are constrained, and approaches
for enhancing fits of SMEFT coefficients are investigated. Studies on the effects of correlations
between the uncertainties of measurements on the results of SMEFT fits are conducted. It is
demonstrated that the correlations can significantly impact the resulting constraints and can
be the crucial components deciding whether deviations from the Standard Model of particle
physics are observed or not, in particular when assuming future measurements with reduced
uncertainties. Moreover, studies on combining measurements of top-quark and flavor physics
observables for SMEFT interpretations are performed, and the steps necessary for a combined
fit are discussed. Powerful synergies between top-quark processes and b → s transitions are
observed when constraining SMEFT Wilson coefficients of the top-quark sector. It is demonstrated that due to complementary sensitivities, combining observables from different energy
scales can tighten the constraints significantly. Future scenarios assuming measurements from
HL-LHC, Belle II, and CLIC are investigated, and their potential for improving constraints
on up to eleven SMEFT Wilson coefficients is pointed out. The benefits of orthogonal constraints in multidimensional phase spaces for resolving ambiguous solutions are highlighted.
The SMEFT studies presented in this thesis demonstrate the capabilities of the new BAT.jl
and EFTfitter.jl packages for BSM analyses.2021-01-01T00:00:00ZDevelopment and calibration of an s-tagging algorithm and its application to constrain the CKM matrix elements |Vts| and |Vtd| in top-quark decays using ATLAS Run-2 DataZeißner, Sonja Verenahttp://hdl.handle.net/2003/403512021-07-29T22:12:18Z2021-01-01T00:00:00ZTitle: Development and calibration of an s-tagging algorithm and its application to constrain the CKM matrix elements |Vts| and |Vtd| in top-quark decays using ATLAS Run-2 Data
Authors: Zeißner, Sonja Verena
Abstract: In this thesis, the development and calibration of an algorithm used to identify jets from strange quarks as well as a measurement constraining the CKM matrix elements $|V_{ts}|$ and $|V_{td}|$ in top-quark decays are presented.
The thesis considers data from proton-proton collisions at the Large Hadron Collider at a center-of-mass energy of 13 TeV recorded by the ATLAS Experiment during Run 2.
First, the maximally achievable separation between jets from strange quarks and jets from down quarks at hadron colliders given different idealized detector designs is studied using recurrent neural networks containing Long Short-Term Memory layers.
Afterwards, an algorithm to select jets from strange quarks for the application at the ATLAS Experiment is developed using deep neural networks.
Its efficiency for these jets from strange quarks and mis-tag rates for jets of other flavors is determined in semileptonic decays of top-antitop pairs selected from data.
The algorithm to identify jets from strange quarks is then applied in events containing decays of top-antitop pairs with an electron and a muon of opposite-sign electric charge in the final state in order to study its potential to constrain the CKM matrix elements $|V_{ts}|$ and $|V_{td}|$ in the two-dimensional plane spanned by them. In this study, limits of $|V_{ts}|^2+|V_{td}|^2<0.06$, $|V_{ts}|<0.21$, and $|V_{td}|<0.24$ are derived at 95% confidence level assuming unitarity of the CKM matrix.
Kurzfassung
Diese Dissertation befasst sich mit der Entwicklung und Kalibrierung eines Algorithmus zur Identifikation von Jets aus strange-Quarks sowie einer Messung zur Bestimmung von oberen Schranken auf die CKM-Matrixelemente $|V_{ts}|$ und $|V_{td}|$ in top-Quark-Zerfällen.
In dieser Arbeit werden Daten aus Proton-Proton-Kollisionen am Large Hadron Collider, die bei einer Schwerpunktsenergie von 13 TeV am ATLAS-Experiment während des Run-2 aufgenommen wurden, verwendet.
Zuerst wird die maximal mögliche Trennung von Jets aus strange-Quarks und Jets aus down-Quarks an Hadronenkollidern unter der Annahme einer Nutzung von unterschiedlichen, idealisierten Detektordesigns untersucht. Hierfür werden Recurrent Neural Networks verwendet, deren Hauptkomponente Long Short-Term Memory Layers sind.
Anschließend wird ein Algorithmus zur Selektion von Jets aus strange-Quarks zur Anwendung am ATLAS-Experiment entwickelt, der Deep Neural Networks verwendet.
Die Identifikationseffizienz dieses Algorithmus in Bezug auf Jets aus strange-Quarks und die Wahrscheinlichkeit, Jets eines anderen Ursprungs fehl zu identifizieren, werden in semileponischen Zerfällen von top-antitop-Paaren, die aus dem aufgenommenen Datensatz selektiert wurden, bestimmt.
Schlussendlich wird der Algorithmus zur Identifikation von Jets aus strange-Quarks in Ereignissen angewendet, die dileponischen Zerfällen von top-antitop-Paaren mit einem Myon und einem Elektron im Endzustand beinhalten. Hierbei wird sein Potenzial in der Bestimmung von Schranken auf die CKM-Matrixelemente $|V_{ts}|$ und $|V_{td}|$ im zweidimensionalen Raum untersucht. Daraus folgen Schranken von $|V_{ts}|^2+|V_{td}|^2<0.06$, $|V_{ts}|<0.21$ und $|V_{td}|<0.24$ mit einem Konfidenzintervall von 95% unter der Annahme von CKM-Matrix-Unitarität.2021-01-01T00:00:00ZStudy of interference effects in the search for flavour-changing neutral current interactions involving the top quark and a photon or a Z boson at the LHCBarros, MauraCastro, Nuno FilipeErdmann, JohannesGeßner, GregorKröninger, KevinLa Cagnina, SalvatorePeixoto, Anahttp://hdl.handle.net/2003/401352021-04-06T22:10:20Z2020-03-30T00:00:00ZTitle: Study of interference effects in the search for flavour-changing neutral current interactions involving the top quark and a photon or a Z boson at the LHC
Authors: Barros, Maura; Castro, Nuno Filipe; Erdmann, Johannes; Geßner, Gregor; Kröninger, Kevin; La Cagnina, Salvatore; Peixoto, Ana
Abstract: Flavour-changing neutral-current interactions of the top quark can be searched for in top-quark pair production with one top quark decaying to an up-type quark and a neutral boson, and they can be searched for in the single production of a top quark in association with such a boson. Both processes interfere if an additional up-type quark is produced in the case of single production. The impact of these interference effects on searches for flavour-changing neutral currents at the LHC is studied for the case where the neutral boson is a photon or a Z boson. Interference effects are found to be smaller than variations of the renormalisation and factorisation scales.2020-03-30T00:00:00ZA selection framework for LHCb’s upgrade triggerNolte, Niklashttp://hdl.handle.net/2003/400592021-03-05T23:10:24Z2020-01-01T00:00:00ZTitle: A selection framework for LHCb’s upgrade trigger
Authors: Nolte, Niklas
Abstract: Das LHCb Experiment am Large Hadron Collier am CERN wird momentan für die nächste Datennahme verändert und modernisiert. Die instantane Luminosität wird um einen Faktor fünf erhöht, damit mehr Daten in kürzerer Zeit aufgenommen werden können. Die erste Stufe der Datennahme, der Hardwaretrigger, wird entfernt. LHCb muss nun eine Kollisionsrate von 30MHz in Echtzeit verarbeiten. In dieser Arbeit werden drei Projekte vorgestellt,die signifikant zu der Entwicklung eines schnellen und effizienten Triggersystems beitragen. Der erste Beitrag ist ein Scheduling Algorithmus mit vernachlässigbarem Overhead in der neuen Trigger-Applikation. Der Algorithmus steuert das Multi-Threading des Systems und ist der erste Algorithmus in LHCb, der den technischen Spezifikationen des Systems genügt. Durch die Restriktion auf Inter-Event Parallelismus können die meisten teuren Entscheidungen schon vor der Laufzeit der Applikation getroffen werden. Der zweite Beitrag besteht aus mehreren Algorithmen zur Filterung und Kombination von Teilchen in der Kollision. Diese Algorithmen sind bis zu mehreren Größenordnungen schneller als die aktuellen, etablierten Algorithmen. Der Einsatz der neuen Algorithmen in der zweiten Trigger-Phase (HLT2) ist ein wichtiger Schritt zur Vervollständigung eines Trigger-Systems, dass den erhöhten Anforderungen entspricht. Das letzte Projekt beschäftigt sich mit der Bandbreite, mit der der Trigger Kollisionen abspeichert. Dazu wird die wichtigste Selektion im HLT2 betrachtet, der topologische Trigger. Dieser Trigger versucht, Zerfälle von beauty Hadronen inklusiv zu selektieren. Zuerst wird der Selektionsalgorithmus selber optimiert. In einem zweiten Schritt werden die Kollisionen, die der Selektion entsprechen, getrimmt. Irrelevante Information für die Analyse von beauty Hadronen in diesen Kollisionen werden entfernt. Damit kann die Bandbreite pro gespeicherter Kollision verringert werden.2020-01-01T00:00:00ZInvestigations of planar n+-in-n ATLAS silicon sensors with modified pixel implantationsWagner, Mareikehttp://hdl.handle.net/2003/400202021-02-02T23:10:24Z2020-01-01T00:00:00ZTitle: Investigations of planar n+-in-n ATLAS silicon sensors with modified pixel implantations
Authors: Wagner, Mareike
Abstract: In hoch energetischen Physikexperimenten werden kontinuierlich verbesserte Sensoren und Module benötigt, um neuen Anforderungen gerecht zu werden. Die REINER-Pixelmodule weisen verschiedene Pixelvariationen auf, um die Sensoreigenschaften, vor allem nach Bestrahlung, zu untersuchen. In dieser Arbeit werden die Labor- und Teststrahlergebnisse von mehreren REINER- Pixelmodulen präsentiert.
Insgesamt wurden dazu neun Module mit Protonen und Neutronen in Bestrahlungseinrichtungen bestrahlt, um die Strahlenhärte und die beabsichtigte Ladungsverstärkung zu untersuchen. Vor der Bestrahlung zeigten alle Pixelvariationen ähnliche Effizienzen in der Ladungssammlung und des Teilchennachweises, was sich jedoch nach der Bestrahlung änderte. Für fast alle Module wurden nach der Bestrahlung die höchsten Teilchennachweiseffizienzen bei niedrigen Spannungen für das Standardpixeldesign gemessen. Nur bei einem mit Neutronen hoch bestrahlten Modul (5x1015neq/cm²) erreicht die Pixelvariation V5 deutlich höhere Nachweiseffizienzen bei niedrigen Spannungen. Die anschließenden Studien, bei denen ein anderes Modul erhitzt wurde, haben gezeigt, dass die höhere Anzahl an Ladungsträgern und die erhöhte Teilchennachweiseffizienz von Pixelvariation V5 ein Aufheizeffekt sind: Für dieses mit Neutronen hoch bestrahlte Modul wurden nach langen Aufheizzeiten eine erhöhte Ladungssammlung und eine höhere Teilchennachweis-effizienz gemessen.
Zusätzlich wurde im Zuge dieser Arbeit ein Aufbau in Betrieb genommen, mit dem die laserinduzierte Ladungssammlungseffizienz eines Sensors mit einer Auflösung im Subpixelbereich im Labor untersucht werden kann. Erste vielversprechende Ergebnisse dieses Aufbaus sind konsistent zu Pixeleffizienzen aus Teststrahlmessungen: Die erhöhte Ladungssammlung- und Teilchennachweiseffizienz von Pixelvariation V5 nach Bestrahlung und Aufheizen ist vermutlich auf elektrische Feldstärkenmaxima zurückzuführen, die an den Ecken und Kanten der n⁺-Implantation auftreten. Dieses stärkere elektrische Feld verbreitert die Verarmungszone und ein Ladungsvervielfältigungseffekt tritt auf.2020-01-01T00:00:00ZFirst evidence of standard model pp → tttt production and performance studies of the ATLAS tile calorimeter for HL-LHCRustige, Lennarthttp://hdl.handle.net/2003/399842021-01-18T23:10:28Z2020-01-01T00:00:00ZTitle: First evidence of standard model pp → tttt production and performance studies of the ATLAS tile calorimeter for HL-LHC
Authors: Rustige, Lennart
Abstract: In diesem Dokument werden zwei Analysen auf dem Gebiet der Teilchenphysik vorgestellt. Erstens, Studien über die Performanz der Rekonstruktion von Myonen unter Verwendung von Kalorimeterinformationen während der HL-LHC Phase des ATLAS Detektors. Zweitens, die Suche nach der simultanen Produktion von vier Top-Quarks, wie vom Standard Modell (SM) prognostiziert, unter Verwendung des vollständigen Run-II-Datensatzes, der von ATLAS aufgenommen wurde. Dieser Datensatz entspricht einer integrierten Luminosität von L = 139 fb-1 von Proton–Proton Kollisionen bei einer Schwerpunktsenergie von √s = 13 TeV.
Für diese Arbeit wird die Performanz der Rekonstruktion von Myonen für verschiedene pile-up Szenarien untersucht, wie sie für die HL-LHC-Phase erwartet werden, und im Hinblick auf verschiedene Rauschszenarien, die den Verlust der Energieauflösung und die Verschlechterung der Detektorakzeptanz aufgrund von Alterung und Bestrahlung der Detektorkomponenten nachbilden. Diese Studie wird durchgeführt, um vorgeschlagene Szenarien für die Aufrüstung des Detektors vor ihrer Implementierung zu testen. Die Suche nach der vom SM prognostizierten Produktion von vier Top-Quarks, konzentriert sich auf die Zerfallsmoden mit zwei Leptonen gleicher Ladung oder mehr Leptonen im Endzustand. Die Suche nach diesem Prozess ist unter anderem durch die sehr hohen involvierten Energien motiviert und durch die Tatsache, dass derzeit verfügbare Datensätze möglicherweise für eine Entdeckung ausreichen. Die finalen Messergebnisse werden mit einem Profile-Likelihood-Fit erzielt, der das Ergebnis eines Boosted-Decision-Trees beinhaltet, welcher darauf trainiert ist zwischen Signal und Untergrund zu unterscheiden. Der Fit führt zu einem Wirkungsquerschnitt von σ(p→tt ¯tt ¯ )=24(+7-6)fb, was einer beobachteten (erwarteten) Signifikanz von Z = 4,3 (Z = 2,4) entspricht. Dies repräsentiert den ersten Nachweis (Evidence) für diesen Prozess. Das erhaltene Ergebnis ist mit der SM Vorhersage innerhalb von 1,7 Standardabweichungen kompatibel.
Auf diesen ersten Nachweis aufbauend, wird die Möglichkeit der Rekonstruktion des vier Top-Quark Systems unter Verwendung eines kinematischen Likelihood Fits entwickelt und getestet. Die Entwicklungen und Tests werden mit dem KLFitter Software Paket durchgeführt und erzielen eine Effizienz der korrekten Zuordnung aller vier Top-Quarks von ε = 33 ± 4 % unter optimalen Bedingungen für den Endzustand mit einem Lepton.; Two analyses in the field of particle physics are presented in this document. First,studies on the performance of the reconstruction of muons using calorimeter inform-ation under the conditions of the High-Luminosity Large-Hadron-Collider (HL-LHC)phase of theATLASdetector. Second, the search for the Standard Model (SM) sim-ultaneous production of four top quarks using the full Run-II data set recorded byATLAS. This data set corresponds to an integrated luminosity ofL= 139 fb−1ofproton–proton collisions at a centre of mass energy of√s= 13 TeV.Here, the performance of the reconstruction of muons is probed for different pile-upscenarios, as those expected for the HL-LHC phase, and in light of different noise scen-arios that emulate the loss of energy resolution and deterioration of detector acceptancedue to ageing and irradiation of detector components. This study is conducted to testproposed detector upgrade scenarios before their implementation.The search for SM like four top quark production presented here, focuses on the de-cay modes with two same sign or more leptons in the final state. The search for thisprocess is, among other factors, motivated by the very large energies involved and bythe fact that it is likely on the verge of being discovered with currently available datasets. The final results are obtained in a profile likelihood fit involving the outcome of aboosted decision tree trained to discriminate between signal and background. The fitresults in a production cross section ofσ(pp→tt tt) = 24+7−6fb, which correspondsto an observed (expected) significance ofZ= 4.3(Z= 2.4). This represents the firstevidence for this process. The obtained result is compatible with the SM prediction within 1.7 standard deviations.Following first evidence, the possibility of reconstructing the four top quark systemusing a kinematic likelihood approach is developed and tested. These developmentsare performed with theKLFitter tool set and yield an efficiency of correctlymatching all four top quarks of ε = 33±4 %under optimal conditions in the singlelepton final state.2020-01-01T00:00:00ZSearches for vector-like quarks with 13 TeV at the ATLAS experiment and development of a boosted-object tagger using a deep neural networkFreundlich, Elena M.http://hdl.handle.net/2003/398032020-11-11T23:10:34Z2020-01-01T00:00:00ZTitle: Searches for vector-like quarks with 13 TeV at the ATLAS experiment and development of a boosted-object tagger using a deep neural network
Authors: Freundlich, Elena M.
Abstract: In this thesis, two searches for the pair production of vector-like top (VLT) and vector-like bottom (VLB) quarks are presented using 36.1 fb⁻¹ and 139 fb⁻¹ of data. The data was taken at √s = 13 TeV in proton-proton collisions with the ATLAS detector, which is one of the major experiments at the Large Hadron Collider at CERN. The decay signature of this search for TT and BB production is characterized by the presence of a Z-boson, which is reconstructed from two opposite-charge same-flavor leptons (e or μ) and is produced alongside a third-generation quark. In addition, the analyses target final-state objects with high transverse momentum, pT.
Within the scope of this thesis, the Multi-Class Boosted-Object Tagger (MCBOT) is developed and characterized. It uses a deep neural network, which identifies reclustered large-radius jets originating from V-bosons, H-bosons, top-quarks and background unambiguously. For the search with 139 fb⁻¹, the multiplicity of hadronic high-pT objects is exploited by defining multiple regions according to the number of MCBOT- and b-tags.
No deviation from the Standard Model expectation is found in the observed data for 36.1 fb⁻¹ and 139 fb⁻¹, and exclusion limits on the pair production cross-section and the mass of VLT and VLB quarks are set depending on various branching-ratio assumptions. With 36.1 fb⁻¹, VLT quark masses below 1102 GeV are excluded with respect to the (T,B) and (X,T) doublet models. For VLB quarks, lower mass limits of 1063 GeV are set for the (B,Y) doublet. The results of this search significantly contribute to the sensitivity of two combination searches for TT and BB production performed at the ATLAS experiment with 36.1 fb⁻¹, which constrain the phase-space for vector-like quark existence further.
For the full Run-2 search with 139 fb⁻¹ of data, lower limits on the VLT quark mass of 1350 GeV are observed and VLB quark masses below 1316 GeV are excluded assuming the mentioned doublet models. The observed limits of this search for TT and BB production represent the highest exclusion limits to date assuming the 100% branching ratio into Zt/b final states and – in case of VLB quarks – for the (B,Y) doublet model.2020-01-01T00:00:00ZDetection and identification of electrons and photonsArling, Jan-Hendrikhttp://hdl.handle.net/2003/397852020-10-27T09:51:07Z2020-01-01T00:00:00ZTitle: Detection and identification of electrons and photons
Authors: Arling, Jan-Hendrik
Abstract: It is important to exploit particle detectors for the detection and identification of electrons and photons in the best possible way, as it is adressed in this thesis by discussing three different application examples of precisely measuring electrons and photons at high-energy physics and
test beam experiments.
Firstly, the optimization of the photon identification within the ATLAS detector at the LHC
is investigated. Appropriate selection criteria are needed to efficiently discriminate prompt photons steming from the hard-scattering collision process from photons originating from hadronic jet decays. Systematic studies for the use of a multivariate optimization with a Boosted Decision Tree are presented and compared to the currently used rectangular cut approach.
Secondly, the planned Inner Tracker (ITk) as an upgrade of the ATLAS detector for the HL-LHC is discussed. The focus of the investigations lies on the support structures foreseen for the silicon sensor modules, the petal core. The thermo-mechanical characterization of the petal is investigated using infrared thermography, dual-phase CO2 cooling and geometrical metrology, proving a well-performing design of the local support structure within the ITk detector specifications.
Finally, measurements with multi-GeV electrons at the DESY II Test Beam Facility are presented to investigate the potential of the Material Budget Imaging technique. This technique aims to reconstruct the material distribution of samples by measuring the deflection angles of traversing electrons with the high-resolution EUDET-type beam telescopes exploiting the underlying effect of multiple Coulomb scattering. The results in terms of the determination of the characteristic radiation length of several materials as well as the two-dimensional material budget image of complex composite structures are shown.; Es ist wichtig, Teilchendetektoren für den Nachweis und die Identifizierung von Elektronen und Photonen bestmöglich zu nutzen, wie es in dieser Arbeit anhand von drei verschiedenen Anwendungsbeispielen für die hochpräzise Messung von Elektronen und Photonen bei Hochenergiephysik- und Teststrahlexperimenten diskutiert wird.
Als Erstes wird die Optimierung der Photonenidentifikation beim ATLAS-Detektor am LHC untersucht. Geeignete Auswahlkriterien werden benötigt um prompte Photonen, die aus dem harten Streuprozess der Kollisionen stammen, effizient von Photonen aus hadronischen Jet-Zerfällen zu unterscheiden. Es werden systematische Studien zur Verwendung einer multivariaten Optimierung mit einem Boosted Decision Tree vorgestellt und mit der derzeit verwendeten Optimierung mittels rechteckiger Schnitte verglichen.
Zweitens wird der geplante Inner Tracker (ITk) als Upgrade des ATLAS-Detektors für den HL-LHC diskutiert. Der Schwerpunkt der Untersuchungen liegt auf den für die Silizium-Sensormodule vorgesehenen Trägerstrukturen, dem Petal Core. Die thermo-mechanische Charakterisierung des Petals wird mittels Infrarot-Thermographie, zweiphasiger CO2-Kühlung und geometrischer Metrologie untersucht, wobei ein gut funktionierendes Design der Haltestruktur innerhalb der ITk-Detektorspezifikationen nachgewiesen wird.
Schließlich werden Messungen mit dem Elektronenstrahl der DESY II-Teststrahlanlage vorgestellt, um das Potenzial der Material Budget Imaging-Technik zu untersuchen. Ziel dieser neuen Technik ist es, die Materialverteilung von Proben zu rekonstruieren, indem die Ablenkwinkel der gestreuten Elektronen mit den hochauflösenden Strahlteleskopen gemessen werden, wobei der zugrundeliegende Effekt der Vielfach-Coulomb-Streuung ausgenutzt wird. Die Ergebnisse hinsichtlich der Bestimmung der charakteristischen Strahlungslänge mehrerer Materialproben sowie der zweidimensionalen Verteilung des Materialbudgets von komplexen Verbundstrukturen werden diskutiert.2020-01-01T00:00:00ZHigh temperature thermoluminescence peaks – influence on the albedo principle for personal dosimetry and benefits for the new TL-DOS neutron dosemeterHeiny, Myriamhttp://hdl.handle.net/2003/392292020-08-07T01:40:51Z2020-01-01T00:00:00ZTitle: High temperature thermoluminescence peaks – influence on the albedo principle for personal dosimetry and benefits for the new TL-DOS neutron dosemeter
Authors: Heiny, Myriam
Abstract: The individual monitoring service at the Materialprüfungsamt North Rhine-Westphalia and the TU Dortmund are developing the compact dosemeter system TL-DOS based on thin-layer thermoluminescence detectors as well as an associated glow curve analysis tool. Various dosemeters of the system measure different dose quantities and types of radiation.
This thesis focuses on the TL-DOS neutron dosemeter to measure the whole body dose. The system is optimized in terms of LiF:Mg,Ti detectors, an albedo badge, a readout device and the glow curve deconvolution. In order to gain more information about the irradiation scenario such as the particle type, the detectors are measured at 653K to include the high temperature peaks. After a design speci_cation was defined, the neutron dosemeter is characterized in di_erent photon and neutron radiation fields as well as in workplace fields.
This thesis also presents an analysis that provides the individual induced signal of mixed field irradiations by analyzing the high temperature peaks of a glow curve. The signal induced by irradiation combinations like alpha+photon or neutron+photon fields is separated with only one detector. Finally, the current dealing with the significant energy dependence of neutron dosemeters is critically discussed and new approaches are presented.; Die Personendosismessstelle des Materialprüfungsamtes Nordrhein-Westfalen und die TU Dortmund entwickeln basierend auf Thermolumineszenzdetektoren das kompakte Dosimetersystem TL-DOS sowie ein dazugehöriges Glühkurvenanalysetool. Das System beinhaltet verschiedene Dosimetertypen, um unterschiedliche Dosisgrößen und Strahlungsarten zu messen.
In dieser Arbeit wird das TL-DOS Neutronendosimeter zur Messung der Ganzkörperpersonendosis betrachtet. Das Dosimetersystem wird bezüglich der LiF:Mg,Ti-Detektoren, einer Albedo-Sonde, einem Auslesegerät und der Glühkurvenanalyse optimiert. Die verwendeten Detektoren werden bei 653K gemessen, sodass auch die Glühkurvensignale bei hohen Temperaturen (>573 K) ausgelesen werden. Dies eröffnet die Möglichkeit, Zusatz-Informationen über die Bestrahlung wie z.B. den Teilchentyp zu erhalten. Nachdem eine Auswertevorschrift festgelegt worden ist, wird das Neutronendosimeter in verschiedenen Photonen- und Neutronenstrahlungsfeldern sowie Arbeitsplatzfeldern charakterisiert.
Des Weiteren wird eine Analyse vorgestellt, die das induzierte Signal nach einer Mischfeld- Bestrahlung wie z.B. Alpha+Photonen- oder Neutronen+Photonen-Feldern separiert. Durch das Auswerten der "high temperature peaks" wird die Trennung mittels eines Detektors möglich.
Zum Schluss wird die aktuelle Vorgehensweise der starken Energieabhängigkeitvon Neutronen Dosimetern diskutiert und neue Lösungsansätze werden vorgestellt.2020-01-01T00:00:00ZTemperature scaling of leakage current in irradiated silicon sensorsWizemann, Felixhttp://hdl.handle.net/2003/385722020-02-18T06:58:04Z2019-01-01T00:00:00ZTitle: Temperature scaling of leakage current in irradiated silicon sensors
Authors: Wizemann, Felix
Abstract: Mit dem Ausbau zum High Luminosity LHC (HL-LHC) wird der Spurdetekor des ATLAS-Experiments durch den Inner Tracker (ITk) ersetzt, der Pixel- und Streifensensoren aus Silizium nutzen wird. In Dortmund werden Module für die Endkappe des ITK Streifendetektors gebaut werden. In einem Teil der Arbeit wird der Ablauf derProduktion dieser Module entwickelt. Während des Betriebs werden Strahlenschäden den Leckstrom der Siliziumsensoren erhöhen. Mit Hilfe des Parameters Eeff kann dieser mit der Temperatur skaliert werden.
Studien haben gezeigt, dass dieser Parameter 1.21 eV für Sensoren beträgt,
die zu einer Fluenz von bis zu 1 x 1015 neqcm-2 bestrahlt wurden. Bei höherer Bestrahlung
wurde ein niedriger Wert für Eeff beobachtet. Um diese Änderung in der
Skalierung mit der Temperatur zu untersuchen, wird Eeff in dieser Arbeit für bestrahlte Sensoren mit Fluenzen zwischen 6 x 1014 neqcm-2 und 3 x 1015 neqcm-2 in Abhängigkeit von der angelegten Spannung bestimmt. Es wird beobachtet, dass Eeff spannungsabhängig ist und 1:21 eV nur oberhalb der Depletionsspannung anwendbar ist.2019-01-01T00:00:00ZSearch for flavour-changing neutral currents in processes with a single top quark in association with a photon using a deep neural network at the ATLAS experiment at √s = 13TeVGeßner, Gregorhttp://hdl.handle.net/2003/385222020-01-17T07:17:17Z2019-01-01T00:00:00ZTitle: Search for flavour-changing neutral currents in processes with a single top quark in association with a photon using a deep neural network at the ATLAS experiment at √s = 13TeV
Authors: Geßner, Gregor
Abstract: In this thesis, a search for flavour-changing neutral currents in processes involving a singly produced top quark and a photon is presented. In this search, proton-proton collision data are used which were collected by the ATLAS experiment at the LHC and correspond to an integrated luminosity of 81 fb⁻¹. The top quark is assumed to decay into a b quark and a W boson, which is supposed to decay leptonically. Events are selected whose final state contains exactly one photon, one charged lepton, one b-tagged jet and a certain magnitude of missing transverse momentum. The background contributions, that arise from events with either an electron or a jet misidentified as photon, are estimated using data-driven techniques. The signal is modelled in an effective field theory. The signal coupling is assumed to be either left- or right-handed and to involve either an up quark or a charm quark. Assuming only one of these signal couplings being present at a time, a discriminant is constructed using a deep neural network which classifies events into signal and background candidates. A profile likelihood fit is performed to improve the background prediction and to estimate the signal strength. Since no signal contribution is observed in data and the data are found to be consistent with the background expectation, upper exclusion limits are set on the branching ratios B(t→uγ) and B(t→cγ). The observed limits at a confidence level of 95 % on the branching ratio are B(t→uγ, left-handed) < 2.8 · 10⁻⁵, B(t→uγ, right-handed) < 6.1 · 10⁻⁵, B(t→cγ, left-handed) < 22 · 10⁻⁵ and B(t→cγ, right-handed) < 18 · 10⁻⁵. These limits are interpreted as limits on the cross section for the production of a top quark and a photon via a flavour-changing neutral current, and as limits on the absolute value of the sum of the Wilson coefficients CuBij* and CuWij* for the left-handed and CuBij and CuWij for the right-handed couplings.; In dieser Disseration wird die Suche nach quarkflavourverändernden neutralen Strömen vorgestellt, die in Prozessen mit einem einzeln produzierten Top-Quark und einem Photon auftreten. Die untersuchten Daten wurden am ATLAS-Detektor am LHC in Proton-Proton Kollisionen aufgezeichnet und entsprechen einer integrierten Luminosität von 81 fb⁻¹. Es wird angenommen, dass das Top-Quark in ein b-Quark und ein W-Boson zerfällt, das wiederum leptonisch zerfällt. Es werden Ereignisse selektiert, deren Endzustand aus genau einem Photon, einem geladenen Lepton, einem b-tagged Jet und einem Mindestbetrag an fehlendem transversalen Impuls besteht. Die Untergrundbeiträge von Ereignissen, in deren Endzustand entweder ein Elektron oder ein Jet fälschlicherweise als Photon identifiziert wurde, werden mit Daten-basierten Techniken abgeschätzt. Das Signal wird im Kontext einer effektiven Feldtheorie modelliert. Die angenommene Signalkopplung ist entweder links- oder rechtshändig und involviert entweder ein Up-Quark oder ein Charm-Quark. Unter der Annahme, dass nur eine dieser Signalkopplungen zeitgleich präsent ist, wird jeweils ein tiefes neuronales Netz trainiert, um Ereignisse als Signal- oder Untergrundkandidaten zu klassifizieren. In einem Profile-Likelihood-Fit wird die Untergrundvorhersage verbessert und die Signalstärke abgeschätzt. Weil kein Signalbeitrag in Daten gefunden wurde und die Untergrundvorhersage mit den Daten übereinstimmen, werden obere Ausschlussgrenzen auf die Verzweigungsverhältnisse B(t→uγ) und B(t→cγ) gesetzt. Die beobachteten Ausschlussgrenzen auf das Verzweigungsverhältnis mit einem Konfidenzniveau von 95 % sind B(t→uγ, linkskhändig) < 2,8 · 10⁻⁵, B(t→uγ, rechtshändig) < 6,1 · 10⁻⁵, B(t→cγ, linkshändig) < 22 · 10⁻⁵ und B(t→cγ, rechtshändig) < 18 · 10⁻⁵. Diese Ausschlussgrenzen werden als Ausschlussgrenzen auf den Produktionswirkungsquerschnitt eines Top-Quarks und eines Photons durch einen quarkflavourverändernden neutralen Strom und als Ausschlussgrenzen auf den Absolutwert der Summe der Wilson-Koeffizienten CuBij* und CuWij* für die linkskhändigen und CuBij und CuWij für die rechtshändigen Kopplungen interpretiert.2019-01-01T00:00:00ZThe COBRA extended demonstrator – conception, characterization, commissioningTemminghoff, Roberthttp://hdl.handle.net/2003/385112020-01-10T02:41:33Z2019-12-06T00:00:00ZTitle: The COBRA extended demonstrator – conception, characterization, commissioning
Authors: Temminghoff, Robert
Abstract: Der neutrinolose doppelte Beta-Zerfall ist ein hypothetischer Kernzerfall dessen Nachweis
grundlegende Fragen über bislang unbekannte Eigenschaften von Neutrinos liefern und
auf Physik jenseits des Standard Modells der Teilchenphysik hindeuten würde. Das COBRA
Experiment sucht nach diesem Zerfall mit Hilfe von CdZnTe Halbleiter-Detektoren.
In dieser Arbeit wird ein wesentlich verbesserter Aufbau des Experiments, genannt
Extended Demonstrator (XDEM), präsentiert. Um diesen zur verwirklichen, wurden
wichtige Eigenschaften der verwendeten Detektoren in Labormessungen bestimmt.
Außerdem wurden Simulationen durchgeführt um Aufschluss über die Wahrscheinlichkeit
einen doppelten Beta-Zerfall zu detektieren zu erhalten und eine Abschätzung
des Hintergrundes durch andere Prozesse zu erreichen. Darauf basierend wurden
Daten analysiert, welche über mehr als ein halbes Jahr am LNGS Untergrundlabor
in Italien aufgezeichnet wurden. Im Vergleich zu früheren Versionen des COBRA
Experiments wurde der Hintergrund um mehr als einen Faktor 30 reduziert bei
gleichzeitiger Steigerung der Wahrscheinlichkeit ein Signal zu messen um 50 %. Es wurden
keine Hinweise auf neutrinolosen doppelten Beta-Zerfall gefunden. Stattdessen wurden
untere Grenzen für die Halbwertszeit der Zerfälle von 116Cd und 130Te aufgestellt,
welche für 116Cd 2,7x10^21 yr und für 130Te 8.8x10^21 yr betragen. Dies sind die stärksten
Grenzen auf diese Halbwertszeiten die im Rahmen des COBRA Experiments bestimmt
wurden.2019-12-06T00:00:00ZSearch for Higgs boson production in association with a single top quark and constraints on the H+b-jets background in the H → γγ decay channel at the ATLAS experimentNitsche, Isabelhttp://hdl.handle.net/2003/382102019-09-11T01:40:45Z2019-01-01T00:00:00ZTitle: Search for Higgs boson production in association with a single top quark and constraints on the H+b-jets background in the H → γγ decay channel at the ATLAS experiment
Authors: Nitsche, Isabel
Abstract: In this thesis, the production of a single top quark in association with a Higgs boson (tH) is studied at √s = 13 TeV in the H → γγ decay channel at the ATLAS experiment. Similar to the production of a Higgs boson in association with a top-antitop quark pair (ttH), tH production allows for a direct measurement of the Yukawa coupling, Yt, of the top quark. Due to a destructive interference in tH production, it also provides sensitivity to negative values of the coupling strength modifier κt = Yt/Yt,SM, which describes deviations from the Standard Model (SM) expectation Yt,SM. For the first time at the ATLAS experiment, dedicated tH categories are included in the measurement of top-quark-associated Higgs boson production in the H → γγ channel, using 36.1/fb of data. The measured signal strength for ttH+tH production agrees with the SM expectation and no hint for a negative sign of κt was found. An important background for hadronic ttH and tH final states in the H → γγ channel is the production of a Higgs boson in association with additional b-jets (H+b-jets). This background is associated with a large systematic uncertainty, as the accuracy of the prediction from Monte Carlo (MC) simulations is not known. A measurement of the differential cross section of the number of b-jets, Nb-jets, for inclusive Higgs boson production in the H → γγ decay channel using 79.8/fb of ATLAS data is presented. The measured cross section for Nb-jets = 1, with the dominant contribution resulting from H+b-jets production, is in agreement with the MC expectation within the uncertainties. Additionally, an approach to improve the sensitivity to H+b-jets is presented, which is based on multivariate analysis techniques to discriminate between H+b-jets and the non-resonant background.; In dieser Dissertation wird die Produktion eines einzelnen Top-Quarks in Verbindung mit einem Higgs-Boson (tH) im H → γγ-Zerfallskanal bei √s = 13 TeV am ATLAS-Experiment untersucht. Neben der Produktion eines Higgs-Bosons in Verbindung mit einem Top-Quark-Paar (ttH) ermöglicht die tH-Produktion eine direkte Messung der Yukawa-Kopplung des Top-Quarks Yt. Aufgrund einer destruktiven Interferenz in der tH-Produktion ist dieser Prozess zusätzlich sensitiv auf negative Werte des Kopplungsstärken-Modifikators κt = Yt/Yt,SM, welcher Abweichungen vom erwarteten Wert im Standardmodell (SM) Yt,SM beschreibt. In der hier vorgestellten Messung der ttH+tH-Produktion im H → γγ-Kanal mit einem Datensatz von 36.1/fb wurden am ATLAS-Experiment erstmals optimierte tH-Kategorien berücksichtigt. Die gemessene Signalstärke für die ttH+tH-Produktion stimmt mit der SM-Erwartung überein und es wurde kein Hinweis auf ein negatives Vorzeichen von κt gefunden.
Die Produktion eines Higgs-Bosons in Verbindung mit zusätzlichen b-jets (H+b-jets) ist ein wichtiger Untergrund für hadronische tH- und ttH-Endzustände. Dieser Untergrund ist mit einer großen systematischen Unsicherheit verbunden, da nicht bekannt ist wie zutreffend die Vorhersagen aus Monte-Carlo-Simulationen sind. Eine Messung des differentiellen Wirkungsquerschnittes (WQ) der Anzahl von b-jets, Nb-jets, für inklusive Higgs-Boson-Produktion im H → γγ-Zerfallskanal mit einem Datensatz von 79.8/fb wird präsentiert. Der dominante Beitrag für Ereignisse mit Nb-jets = 1 resultiert dabei aus der H+b-jets-Produktion. Der gemessene WQ für Nb-jets = 1 stimmt innerhalb der Unsicherheiten mit der Monte-Carlo-Vorhersage überein. Zusätzlich wird ein Ansatz zur Erhöhung der Sensitivität auf H+b-jets präsentiert, der auf einer Trennung von H+b-jets und dem nicht-resonanten Untergrund mittels multivariater Analysemethoden basiert.2019-01-01T00:00:00ZCompletion of the muon veto for the Dortmund Low Background Facility and proton activation measurements on irradiated metals from proton beam therapyNitsch, Christianhttp://hdl.handle.net/2003/380072019-04-09T01:40:48Z2018-01-01T00:00:00ZTitle: Completion of the muon veto for the Dortmund Low Background Facility and proton activation measurements on irradiated metals from proton beam therapy
Authors: Nitsch, Christian
Abstract: The Dortmund Low Background Facility is a highly sensitive gamma ray spectrometry system, operated in a low-background environment, which enables the measurement of traces of radioactivity with high precision.
A HPGe detector is set up within an artificial overburden, equivalent to 10 meters of water.
This outer shielding reduces the contribution from cosmic muons during the measurement.
Signals induced by cosmic muons that penetrate this shielding are suppressed by an active cosmic muon veto detector.
Environmental radioactivity is effectively shielded from the germanium detector with an multi-layered inner shielding, which is featuring a neutron absorber inside a massive lead shielding.
During this work, the muon veto detector is completed with newly installed plastic scintillator detectors.
The upgraded veto detector in combination with passive shielding techniques results in a remarkably low residual background count rate of 1.855 counts/(kg min) between 40 keV and 2700 keV.
Subsequently, detection limits below 1 mBq/kg are achieved.
A detailed analysis of the remaining background spectrum is presented within this work, including MC simulations, that are used to estimate the origins of different background contributions.
The irradiation of brass apertures wich high energetic protons during clinical proton beam therapy can create a radiation protection risk for personnel and patients.
In cooperation with the WPE several metal samples are irradiated.
Due to the high sensitivity of the Dortmund Low Background, relatively short-lived radionuclides are identified and analysed within two irradiated brass aperture samples.
The results, presented in this work, are also compared with FLUKA simulations and used for the estimation of the ambient dose rate caused by the activated samples.2018-01-01T00:00:00ZQuad module prototypes and design improvement studies of planar n+-in-n silicon pixel sensors for the ATLAS Inner Tracker upgradeGisen, Andreashttp://hdl.handle.net/2003/373512018-11-01T02:40:53Z2018-01-01T00:00:00ZTitle: Quad module prototypes and design improvement studies of planar n+-in-n silicon pixel sensors for the ATLAS Inner Tracker upgrade
Authors: Gisen, Andreas
Abstract: In order to meet the requirements of the High Luminosity-LHC (HL-LHC), it will be
necessary to replace the current tracker of the ATLAS experiment. Therefore, a new
all-silicon tracking detector is being developed, the so-called Inner Tracker (ITk). The
use of quad chip modules is intended in its pixel region. These quad modules consist of
four read-out chips, bump-bonded to one large silicon pixel sensor.
In this thesis, first prototypes of quad modules are investigated, which were assembled
using a planar n+-in-n silicon pixel sensor and four FE-I4 read-out chips. The focus
of the investigations is the measurement of charge collected in the laboratory and the
tracking efficiency for particle passages at testbeams.
In addition, the development of new pixel designs is presented.; Um die Anforderungen des High Luminosity-LHC (HL-LHC) zu erfüllen, wird es
notwendig sein, den aktuellen Tracking-Detektor des ATLAS-Experiments zu ersetzen.
Deshalb wird ein neuer Silizium-Tracking-Detektor entwickelt, der sogenannte
Inner Tracker (ITk). In dessen Pixelbereich ist der Einsatz von Quad-Chip-Modulen
vorgesehen. Diese Quad-Module bestehen aus vier Auslese-Chips, die über Bump Bonds
mit einem großen Silizium-Pixelsensor verbunden sind.
In dieser Arbeit werden erste Prototypen solcher Quad-Module untersucht, die unter
Verwendung eines planaren n+-in-n-Silizium-Pixelsensors und vier FE-I4-Auslesechips
gefertigt wurden. Der Fokus der Untersuchungen liegt auf Messung der Ladungssammlung
im Labor und der Nachweiseffizienz von Teilchendurchgängen im Testbeam.
Darüber hinaus wird die Entwicklung neuer Pixel-Designs vorgestellt.2018-01-01T00:00:00ZEstimation of fading time and irradiation dose in thermoluminescence dosimetry using uni- and multivariate analysis techniquesTheinert, Roberthttp://hdl.handle.net/2003/373502018-11-01T02:40:55Z2018-01-01T00:00:00ZTitle: Estimation of fading time and irradiation dose in thermoluminescence dosimetry using uni- and multivariate analysis techniques
Authors: Theinert, Robert
Abstract: Fading influences are a crucial point in dosimetry using thermoluminescence dosemeters. Due to thermal fading, the thermoluminescence signal decreases over time resulting in a potential underestimation of the irradiation dose.
This thesis presents two techniques for a fading time independent irradiation dose estimation. Both methods are based on glow curve deconvolution.
In the first approach, the fraction of signal photons of two peaks in the glow curve is used to estimate fading time and irradiation dose. The second approach is based on a multivariate analysis using a neural network with multiple features as inputs to predict the fading time and the irradiation dose.
The measurements presented in this thesis are performed within the context of the TL-DOS project, in which the monitoring service of the Materialprüfungsamt North Rhine-Westphalia and the Lehrstuhl Experimentelle Physik IV at the TU Dortmund are developing a new thermoluminescence dosemeter system for application in routine personal dosimetry.; Bei der Verwendung von Thermolumineszenzdetektoren in der Dosimetrie sind Fadingeinflüsse ein entscheidender Faktor. Durch das thermische Faden nimmt das Thermolumineszenzsignal im Laufe der Zeit ab, was zu einer Unterschätzung der berechneten Dosis führen kann.
In dieser Arbeit werden zwei Techniken vorgestellt, mit denen es möglich ist, eine von der Fadingzeit unabhängige Dosis zu berechnen. Beide Ansätze basieren auf einer Zerlegung der Glühkurve in ihre einzelnen Peaks.
Im ersten Ansatz wird der Anteil der Signalphotonen an der gesamten Glühkurve verwendet, um die Fadingzeit und die Dosis zu bestimmen. Der zweite Ansatz basiert auf einer Multivariaten Analyse, in der ein neuronales Netz mit mehreren Eingangsvariablen benutzt wird, um die Fadingzeit und die Dosis vorherzusagen.
Die Messungen in dieser Arbeit wurden im Rahmen des TL-DOS Projektes durchgeführt, in dem die Personendosismessstelle des Materialprüfungsamts Nordrhein-Westfalen und der Lehrstuhl Experimentelle Physik IV an der TU Dortmund ein Thermolumineszenzdosimetriesystem entwickeln, das in der amtlichen Personendosimetrie eingesetzt werden soll.2018-01-01T00:00:00ZMeasuring the b-tagging efficiency in ATLAS data at √s = 8TeV and √s = 13 TeV using the ρTrel-methodBurmeister, Ingohttp://hdl.handle.net/2003/359572017-05-09T02:00:08Z2017-01-01T00:00:00ZTitle: Measuring the b-tagging efficiency in ATLAS data at √s = 8TeV and √s = 13 TeV using the ρTrel-method
Authors: Burmeister, Ingo
Abstract: In dieser Dissertation wird die erste Messung der b-tagging Effizienz eff(b) mit der pTrel-Methode am ATLAS Experiment unter Run 2 Bedingungen präsentiert. Die Messung wurde durchgeführt mit semileptonisch zerfallenden b-Hadronen mit einem Myon im Endzustand. Dies wurde erreicht durch Selektion von Myonen in einem Jet Kegel. Die pTrel-Variable is dabei sensitiv auf die Masse des schwach zerfallenden Teilchens und damit auf den Flavor des Jets. Dieser Zusammenhang lässt sich mit einem log-likelihood Fit ausnutzen um die Flavor-Anteile zu bestimmen, in Datensätzen unterteilt von dem betrachteten Klassifizierungsalgorithmus und Arbeitspunkt. Dies wurde durchgeführt auf einem Datensatz, der einer integrierten Luminosität von 11.6 / fb an Proton-Proton Kollisionen entspricht, aufgenommen mit dem ATLAS-Experiment bei einer Schwerpunktsenergie von sqrt(s) = 13 TeV.
Zusätzlich wurde die pTrel-Methode benutzt um eff(b) auf Triggerlevel zu bestimmen. Dies wurde durchgeführt auf einem Datensatz von Proton-Proton Kollisionen, aufgenommen mit dem ATLAS-Detektor bei einer Schwerpunktsenergie von sqrt(s) = 8 TeV. Hier wurde die Messung abhängig von einer off-line Klassifizierung durchgeführt.; This thesis presents the first measurement of the b-tagging efficiency eff(b) with the pTrel-method under Run 2 conditions at the ATLAS experiment. The measurement has been performed for semi-leptonically decaying b-hadrons with a muon in the final state. This has been achieved by selecting events with a muon associated to a jet by a cone based matching algorithm. The pTrel-variable is sensitive to the mass of the weakly decaying particle and is therefore sensitive to the jet-flavor. Exploiting this dependence, the flavor fractions are determined with a log-likelihood template fit to the pTrel-distribution in the tagged and untagged jet samples determined by the algorithm and operating point under study. The dataset used for this study corresponds to an integrated luminosity of 11.6 / fb of proton-proton-collisions taken with the ATLAS detector at sqrt(s) = 13 TeV center of mass energy.
In addition, eff(b) has been measured for algorithms on trigger level using the pTrel-method. This has been conducted in a set of proton-proton-collisions recorded at the ATLAS experiment at sqrt(s) = 8 TeV center of mass energy. Here, a conditional calibration depending on off-line tagger decisions has been utilized.2017-01-01T00:00:00ZCommissioning of the ATLAS Insertable B-Layer and first operation experienceDette, Karolahttp://hdl.handle.net/2003/359282017-04-13T02:00:31Z2017-01-01T00:00:00ZTitle: Commissioning of the ATLAS Insertable B-Layer and first operation experience
Authors: Dette, Karola
Abstract: Todays research in particle physics offers a wide field of opportunities for scientists from a variety of different subjects. Discoveries can only be made, with hundreds up to thousands of people working together in collaborations. Designing high precision detectors that can be up to several stories tall, followed by production, construction, commissioning and successful operation is only achievable with the combined effort of skilled and experienced detector physicists and engineers, while the vast amount of data recorded with those detectors calls for specialists in data analysis which are able to find the needle in a haystack or in other words the higgs in a sea of underground events. One of the biggest science collaborations worldwide is the ATLAS collaboration with more than 5000 members from around 180 institutes. ATLAS is one of four big particle physics experiments at the LHC. Its tracking system has been upgraded with a new innermost layer, referred to as Insertable B-Layer (IBL), in 2014. This thesis will focus on the construction, commissioning and first year of operation of the IBL detector and give a brief outlook on upgrade plans for the tracking system. The performance of the IBL and its services was observed before and after each step of its construction. Quality assurance measurements were performed to select the best working staves for the IBL construction. A system test was performed to verify the correct functionality of the final setup were the IBL was built on. A thorough commissioning testing the supply chain, the readout and the performance of complete detector was carried out in a clean room and repeated after installation in ATLAS. Several steps of re-testing took place after the IBL was exposed to thermal stress. The results of each commissioning step will be presented and discussed. During the first year of operating the IBL, an increase of the low voltage currents in the readout chips was observed. A model to understand this increase will be introduced as well as measurements that were used to develop an operation guideline to protect the detector while continuing to take data. The last part of this thesis will give a brief introduction to an alternative method for module hybridisation that was investigated as a possible option for the next upgrade of the ATLAS tracking system.2017-01-01T00:00:00ZCommissioning of the COBRA demonstrator and investigation of surface events as its main backgroundTebrügge, Janhttp://hdl.handle.net/2003/351502016-07-22T02:00:17Z2016-01-01T00:00:00ZTitle: Commissioning of the COBRA demonstrator and investigation of surface events as its main background
Authors: Tebrügge, Jan
Abstract: The COBRA collaboration investigates 0νββ-decays (neutrinoless double beta-de- cays). Therefore, a demonstrator setup using coplanar-grid CdZnTe detectors is operated at the LNGS underground laboratory. In this work, the demonstrator was commissioned and completed, which is discussed extensively. The demonstrator works reliably and collects low-background physics data. One result of the analysis of the data is that surface events are the dom- inating background component. To better understand and possibly discriminate this background, surface events were studied in detail. This was done mainly us- ing laboratory measurements. For a better interpretation of these measurements, simulations of particle trajectories and ranges were done. The surface sensitivity tests showed large differences between the individual detectors. Often, a dead-layer was determined, especially at the surfaces where the non-collecting anode (NCA) is the outermost anode rail. Due to this, the sensitivity of the surfaces where the collecting anode (CA) is adjacent was typically about a factor of three larger than the NCA sensitivity. A comparison of the pulse shape analysis methods LSE and A/E was done. Laboratory measurements indicate, that the latter performs bet- ter. Alpha scanning measurements were done to spatially investigate the surface sensitivity. Plausible variations were measured. However, no hints were found how to improve the surface event recognition. The instrumentation of the guard ring, which surrounds the anode structure, was tested and improved the surface event discrimination significantly. The fraction of surviving alpha events was at a per-mill level. Furthermore, the electron mobility was determined to (968±28) cm^2/(Vs) is in very good agreement with literature values. A variation at the detector edges was found. Important steps for a future large-scale COBRA experiment are discussed briefly, mainly the use of an integrated read-out system. Overall, the results indicate a large potential in background reduction for the COBRA experiment.2016-01-01T00:00:00ZPixel detector modules performance for ATLAS IBL and future pixel detectorsJentzsch, Jenniferhttp://hdl.handle.net/2003/343232015-11-07T02:40:29Z2015-01-01T00:00:00ZTitle: Pixel detector modules performance for ATLAS IBL and future pixel detectors
Authors: Jentzsch, Jennifer
Abstract: The ATLAS Detector is one of the four big particle physics experiments at CERN’s LHC. Its innermost tracking system consisted of the 3-Layer silicon Pixel Detector (~80M readout channels) in the first run (2010-2012). Over the past two years it was refurbished and equipped with new services as well as a new beam monitor. The major upgrade, however, was the Insertable B-Layer (IBL). It adds ~12M readout channels for improved vertexing, tracking robustness and b-tagging performance for the upcoming runs, before the high luminosity upgrade of the LHC will take place. This thesis covers two main aspects of Pixel detector performance studies: The main work was the planning, commissioning and operation of a test bench that meets the requirements of current pixel detector components. Each newly built ATLAS IBL stave was thoroughly tested, following a specifically developed procedure, and initially calibrated in that setup. A variety of production accompanying measurements as well as preliminary results after integration into the ATLAS Pixel Detector, right before the start of the second LHC run, will be presented and discussed. The second focus of this thesis are pixel detector studies with the help of high energetic particle beams. A 3D prototype sensor from the ATLAS IBL production was studied at various rotation angles to investigate its charge collection properties. During these measurements, tracking information was provided by the Timepix telescope. Preliminary results depicting the detectors performance at various particle incidence angles will be evaluated.2015-01-01T00:00:00ZInvestigation of n +-in-n planar silicon pixel detectors for application in the ATLAS experimentAltenheiner, Silkehttp://hdl.handle.net/2003/343222015-11-07T02:40:29Z2015-01-01T00:00:00ZTitle: Investigation of n +-in-n planar silicon pixel detectors for application in the ATLAS experiment
Authors: Altenheiner, Silke
Abstract: One of the two large multi-purpose detectors at the LHC at CERN is the ATLAS detector. The ATLAS detector consists of several sub-detectors, each with diffe- rent tasks. The ATLAS pixel detector was enlarged with a fourth pixel layer, the Insetable B-Layer (IBL) during the first long shutdown. The IBL will increase the tracking performance under high-luminosity conditions. The IBL consists to 75% of n+-in-n slim edge planar pixel sensors. Sensors with a thickness of 200 µm and a requested fluence of 5 x 10 15 n eq cm2 were investigated in terms of leakage current per pixel, power dissipation, and average hit efficiency at bias voltages up to 1000V and a temperature of -15°C. Testbeam and laboratory measurements for the sensor decision for the IBL are presented.2015-01-01T00:00:00ZMeasurement of the top quark mass in topologies enhanced with single top quarks produced in the t-channel using flavour tagging and a neural network with ATLAS data at √s = 8TeVEsch, Hendrikhttp://hdl.handle.net/2003/338112015-08-12T20:00:57Z2015-01-01T00:00:00ZTitle: Measurement of the top quark mass in topologies enhanced with single top quarks produced in the t-channel using flavour tagging and a neural network with ATLAS data at √s = 8TeV
Authors: Esch, Hendrik
Abstract: In this thesis a measurement of the top quark mass in topologies that have been enhanced with single-top quark decays in the t-channel produced via weak interactions is presented.
The dataset consists of proton-proton collisions at a centre-of-mass energy of sqrt(s) = 8 TeV collected with the ATLAS detector at the LHC with a total integrated luminosity of L = 20.3 1/fb. Selected events contain exactly one charged lepton - which can be either an electron or a muon -, missing transverse energy and two jets with exactly one of the two being b-tagged. The techniques of b-tagging used to identify jets induced by heavy quarks is explained further. In addition, the signal is enhanced using a neural network based discriminant that combines the ability to discriminate between signal and background of several correlated variables.
To determine the mass of the top quark a template method is used in combination with the mass sensitive variable, m(l b), which is the invariant mass of the lepton and the b-tagged jet.
The top quark mass is measured as m(top) = [172.2 +/- 0.7 (stat.) +/- 1.9 (syst.)] GeV.2015-01-01T00:00:00ZMaterial screening by means of low-level gamma ray spectrometry with the Dortmund Low Background HPGe FacilityNeddermann, Tillhttp://hdl.handle.net/2003/334822015-08-12T23:55:03Z2014-07-11T00:00:00ZTitle: Material screening by means of low-level gamma ray spectrometry with the Dortmund Low Background HPGe Facility
Authors: Neddermann, Till
Abstract: Many experiments try to investigate the nature of dark matter by searching for rare interactions of hypothetical WIMPs or probe the nature of the neutrino by hunting for the neutrinoless double beta decay. The expected signals lie in the range of approximately 1 keV to 5 MeV, which is the same as the decay energies of radioactive nuclides and other nuclear reactions. Therefore, any energy deposition in the used detectors by particles emitted in a radioactive decay occurring in or near the detectors has to be avoided to lower the background as much as possible.
To support the construction of the COBRA experiment - a second generation project searching for the 0νββ decay - the Dortmund Low Background HPGe Facility (DLB) was designed and set-up. It is a low-level gamma ray spectrometry system intended for the detection of traces of radioactivity and therefore enabling the selection of construction materials.
The necessary low background environment for the germanium detector was achieved by setting up a massive graded shielding containing different qualities of lead, copper and a neutron moderating as well as absorbing layer. To reduce the contribution of cosmic rays to the background spectrum an artificial overburden of up to 10m of water equivalent was constructed, which attenuates the soft component of the cosmic rays effectively. To suppress signals induced by muons penetrating the outer shielding an active veto detector using plastic scintillator sheets was set-up.
With these measures a remarkably low integral background level of 4.06cts/(min kg) (40keV - 2700keV) has been achieved. Analysing the background spectrum only very small remaining gamma ray peaks can be found. Based on this a thermal neutron flux at the HPGe detector was determined, which is nearly two orders of magnitude below the value of conventional detector systems. The calculated upper limit on the flux of fast neutrons is nearly equal to the upper limit for a system with 500mwe of overburden.
To allow the reliable determination of nuclide activities from the acquired low background gamma ray spectra a data analysis software based on the DIN ISO 11929:2011 standard was developed. With the software the detection efficiency between sample and germanium detector can be determined on the basis of Monte Carlo simulations.
The Monte Carlo model of the detector system was optimized in several steps by comparing spectra of different nuclides in certain measurement geometries with the Monte Carlo output. By this the discrepancies between simulation and measurement of up to 28% with the initial detector model could be reduced to maximum 3%.
With these efforts a detector system was set-up which is able to detertmine radioimpurities as low as a few millibequerel per kilogram sample mass and therefore is able to provide valuable data for ultra low background experiments although the system was set-up at the surface.2014-07-11T00:00:00ZInvestigation of radiation damage in n+-in-n planar pixel sensors for future ATLAS pixel detector upgradesRummler, Andréhttp://hdl.handle.net/2003/334262015-08-12T23:44:18Z2014-06-10T00:00:00ZTitle: Investigation of radiation damage in n+-in-n planar pixel sensors for future ATLAS pixel detector upgrades
Authors: Rummler, André
Abstract: The ATLAS detector is a multi-purpose detector within the large hadron collider at CERN in Geneva. Its inner-most sub detector is the pixel detector which is an important part of the tracker system. It is a hybrid detector where readout electronics and sensors are manufactured separately and connected subsequently through bump bonds. Due to the location next to the interaction point sensors have to withstand high radiation. Test sensors were irradiated with neutrons at the JSI in Ljubljana and with protons at the irradiation center Karlsruhe and at CERN-PS. The radiation hardness of planar silicon n-in-n sensors was demonstrated in this thesis up to a fluence of 2E16 n_eq/cm², which is the expected end of life fluence for the inner layer after the HL-LHC upgrade of ATLAS. More charge than calculated with a simple trapping model is collected, indicating that some sort of stable charge amplification is taking place. The measurements were done with a beta particle source and with high energy beams of electrons and pions at test beam sites. An excellent hit efficiency of 97% was achieved.2014-06-10T00:00:00ZMeasurement of the mass of the top quark using the transverse decay length and lepton transverse momentum techniquesJung, Christianhttp://hdl.handle.net/2003/330962015-08-12T16:57:06Z2014-05-07T00:00:00ZTitle: Measurement of the mass of the top quark using the transverse decay length and lepton transverse momentum techniques
Authors: Jung, Christian2014-05-07T00:00:00ZSlim edge studies, design and quality control of planar ATLAS IBL pixel sensorsWittig, Tobiashttp://hdl.handle.net/2003/303622015-08-12T19:14:16Z2013-06-04T00:00:00ZTitle: Slim edge studies, design and quality control of planar ATLAS IBL pixel sensors
Authors: Wittig, Tobias
Abstract: One of the four large experiments at the LHC at CERN is the ATLAS detector, a multi purpose detector. Its pixel detector, composed of three layers, is the innermost part of the tracker. As it is closest to the interaction point, it represents a basic part of the track reconstruction. Besides the requested high resolution one main requirement is the radiation hardness. In the coming years the radiation damage will cause deteriorations of the detector performance. With the planned increase of the luminosity, especially after the upgrade to the High Luminosity LHC, this radiation damage will be even intensified. This circumstance necessitates a new pixel detector featuring improved radiation hard sensors and read-out chips.
The present shutdown of the LHC is already utilized to insert an additional b-layer (IBL) into the existing ATLAS pixel detector. The current n-in-n pixel sensor design had to be adapted to the new read-out chip and the module specifications. The new stave geometry requests a reduction of the inactive sensor edge. In a prototype wafer production all modifications have been implemented. The sensor quality control was supervised which led to the decision of the final sensor thickness. In order to evaluate the performance of the sensor chip assemblies with an innovative slim edge design, they have been operated in test beam setups before and after irradiation. Furthermore, the quality control of the planar IBL sensor wafer production was supervised from the stage of wafer delivery to that before the flip chip process to ensure a sufficient amount of functional sensors for the module production.2013-06-04T00:00:00ZSensitivity studies of CdZnTe semiconductor detectors for the COBRA experimentKöttig, Tobiashttp://hdl.handle.net/2003/297522015-08-12T18:55:58Z2012-11-13T00:00:00ZTitle: Sensitivity studies of CdZnTe semiconductor detectors for the COBRA experiment
Authors: Köttig, Tobias
Abstract: The COBRA Experiment searches for Neutrinoless Double Beta Decay. The observation of this decay would provide the absolute mass of the neutrino and clarify the question whether the neutrino is its own anti particle, a so called Majorana particle, or not. For the search COBRA applies CdZnTe room temperature semiconductor detectors. CdZnTe can be operated as a pixelated detector or with
a Coplanar Grid (CPG) readout. Both detector types are a possible option for the COBRA Experiment, and in this work their prospects and suitability was investigated.
Data measured with a large volume pixel detector was reproduced in Geant4 Monte Carlo simulations. With these simulations the veto capabilities and the most dangerous background contributions for COBRA were determined. It was shown that the background level can be reduced by several orders of magnitude by applying fiducial volume cuts. This is especially efficient for the reduction of background from alpha particles. The main remaining background for pixel detectors was found to derive from rare high energetic gamma radiation.
For the COBRA CPG set-up at the Italian underground laboratory LNGS, a major contribution in the development of new readout electronics was made. Data taken with this new electronics was evaluated to determine the largest remaining background sources of the COBRA LNGS test set-up. As main background sources alpha-decays of Pt-190 and Po-210 were identified and their influence could be significantly reduced.
For the rare alpha decay of Pt-190 a half-life of (5.8 +- 1.0 (stat.) +- 0.7 (syst.)) *10^11 years was determined.
The search for small signals in sparse data requires special analysis methods. For the analysis of COBRA data a new unbinned extended maximum likelihood fitter was developed, thoroughly tested with Monte Carlo data and applied to LNGS data. With the achieved background reduction and the
new analysis method, former COBRA half life limits for neutrinoless double beta decay were improved by more than a factor of two. For Cd-116 and Te-130 upper limits of 2.4*10^20 years and 1.1*10^21 years were obtained respectively.2012-11-13T00:00:00ZDevelopment and operation of a testbeam setup for qualification studies of ATLAS pixel sensorsTroska, Georghttp://hdl.handle.net/2003/293512015-08-12T18:10:37Z2012-02-29T00:00:00ZTitle: Development and operation of a testbeam setup for qualification studies of ATLAS pixel sensors
Authors: Troska, Georg2012-02-29T00:00:00ZExploration of new data acquisition and background reduction techniques for the COBRA experimentSchulz, Oliverhttp://hdl.handle.net/2003/291082015-08-12T17:54:02Z2011-09-20T00:00:00ZTitle: Exploration of new data acquisition and background reduction techniques for the COBRA experiment
Authors: Schulz, Oliver
Abstract: This work has contributed improvements to several key aspects of the COBRA
double-beta decay experiment.
A new data acquisition chain was developed for pulse-shape based readout
of the COBRA coplanar grid (CPG) detectors. Prototype electronics for detector
signal transmission and amplification were developed, as well as a software
package with algorithms for pulse shape analysis of CPG detector signals. The
pulse shape data readout has already resulted in significant improvements of the
detector energy resolution. Pulse shape analysis has added interaction depth information
to data output of the experiment, which has already shown itself to
be an effective tool to suppress part of the background. A wavelet-based data
compression technique has been developed to cope with the significant increase
of data volume inherent to the recording of the full detector pulse shapes.
A flexible data acquisition software framework was developed along with the
new DAQ hardware chain. It is designed for both research and development
applications and long-term physics data collection and is now in production use
at several sites in the COBRA collaboration. The framework was also designed to
scale up to the requirements of a large-scale experiment and its modular nature
ensures that future components can be integrated easily.
This work has contributed to the reduction of the radiation background level
by over an order of magnitude, achieved by the combination of new CPG detector
coatings and contacting methods with nitrogen flushing of the COBRA setup to
create a radon-free environment.
For the first time, low-background physics data was taken with a CdZnTe pixel
detector. The results show that pixel detectors present an exciting option for the
future of the experiment.
Work is currently under way to scale up the new CPG electronics to a high
channel count. The COBRA CPG setup at LNGS is scheduled to be upgraded to
a higher number of detectors in 2011, which will all be run using the new DAQ
system. A detailed study of the detector pulse shapes using simulations and collimated
scans, currently in progress, will yield the necessary basis for advanced
CPG pulse shape analysis. This will, in the future, enable new form of background
suppression like separation between single-site and multi-site events.2011-09-20T00:00:00ZB-Tagging calibration at the ATLAS experimentHirsch, Florianhttp://hdl.handle.net/2003/289572015-08-12T17:09:55Z2011-08-05T00:00:00ZTitle: B-Tagging calibration at the ATLAS experiment
Authors: Hirsch, Florian2011-08-05T00:00:00ZInvestigations on the decay length method for the measurement of the top quark mass at the Atlas experimentWalbersloh, Jörghttp://hdl.handle.net/2003/264612015-08-13T00:50:40Z2009-10-21T09:38:17ZTitle: Investigations on the decay length method for the measurement of the top quark mass at the Atlas experiment
Authors: Walbersloh, Jörg
Abstract: The precision of the determination of the top quark mass at particle collider
experiments with methods which rely on jet energy measurements is limited due to
the jet energy scale. This thesis presents a method that relies almost exclusively on
tracking and thus has complementary uncertainties with respect to other methods.
This so-called decay length method correlates the mean transverse decay length of
B-Hadrons originating from top quark decays to the mass of the initial top quark.
The thesis discusses the application the method for the semileptonic decay channel
of tt-Events at the ATLAS detector and presents an estimate for uncertainties
based on MonteCarlo simulations.2009-10-21T09:38:17ZConstruction of a low background facility for the COBRA experiment and its performanceMünstermann, Danielhttp://hdl.handle.net/2003/259422015-08-12T20:44:56Z2008-12-18T11:35:24ZTitle: Construction of a low background facility for the COBRA experiment and its performance
Authors: Münstermann, Daniel
Abstract: The COBRA experiment is investigating neutrinoless double-beta decays of Cd, Zn and Te isotopes with an array of CdZnTe semiconductor detectors. The current development stage consists of 64 CPG-type detectors of 1 ccm size each that will be arranged in form of a 3-dimensional 4 × 4 × 4-array. At the time of writing, the first 16-detector layer was installed and has been collecting data since January 2007. The remaining three layers are currently being assembled.
Within the course of this work, key experimental components for the COBRA setup have been developed, among them several versions of custom-built preamplifiers, shapers and large parts of COBRA’s VME-based ADC. Furthermore, the detector suspension and contacting were completely re-designed and the shielding concept was significantly enhanced.
Based on roughly 4.2 kg · d of data collected with the first operational 16-detector layer, a coincidence-based analysis has been performed focusing on neutrinoless double-beta decays of Cd-116, Te-128 and Te-130 into excited states. For one of the decays, previously published limits on the half-life could be improved. Moreover, the power of the coincidence analysis method was demonstrated for decays involving gamma emission.2008-12-18T11:35:24ZLadungsträgerverlust in strahlengeschädigten SiliziumsensorenWeber, Jenshttp://hdl.handle.net/2003/251852015-08-12T16:32:05Z2008-04-15T11:53:01ZTitle: Ladungsträgerverlust in strahlengeschädigten Siliziumsensoren
Authors: Weber, Jens2008-04-15T11:53:01ZCommissioning perspectives for the ATLAS Pixel DetectorDobos, Danielhttp://hdl.handle.net/2003/251252015-08-12T23:45:40Z2008-03-18T09:21:58ZTitle: Commissioning perspectives for the ATLAS Pixel Detector
Authors: Dobos, Daniel
Abstract: The ATLAS Pixel Detector, the innermost sub-detector of the ATLAS experiment at
the Large Hadron Collider, CERN, is an 80 million channel silicon pixel tracking
detector designed for high-precision charged particle tracking and secondary vertex
reconstruction. It was installed in the ATLAS experiment and commissioning for the
first proton-proton collision data taking in 2008 has begun. Due to the complex layout
and limited accessibility, quality assurance measurements were continuously
performed during production and assembly to ensure that no problematic components
are integrated. The assembly of the detector at CERN and related quality assurance
measurement results, including comparison to previous production measurements,
will be presented. In order to verify that the integrated detector, its data acquisition
readout chain, the ancillary services and cooling system as well as the detector control
and data acquisition software perform together as expected approximately 8% of the
detector system was progressively assembled as close to the final layout as possible.
The so-called System Test laboratory setup was operated for several months under
experiment-like environment conditions. The interplay between different detector
components was studied with a focus on the performance and tunability of the optical
data transmission system. Operation and optical tuning procedures were developed
and qualified for the upcoming commissioning. The front-end electronics preamplifier
threshold tuning and noise performance were studied and noise occupancy of the
detector with low sensor bias voltages was investigated. Data taking with cosmic
muons was performed to test the data acquisition and trigger system as well as the
offline reconstruction and analysis software. The data quality was verified with an
extended version of the pixel online monitoring package which was implemented for
the ATLAS Combined Testbeam. The detector raw data of the Combined Testbeam
and of the System Test cosmic run was converted for offline data analysis with the
Pixel bytestream converter which was continuously extended and adapted according
to the offline analysis software needs.2008-03-18T09:21:58ZThe ATLAS pixel sensorKlaiber-Lodewigs, Jonas M.http://hdl.handle.net/2003/231122015-08-13T00:50:29Z2006-12-01T11:19:56ZTitle: The ATLAS pixel sensor
Authors: Klaiber-Lodewigs, Jonas M.
Abstract: The planning, construction and commissioning of multi-purpose physics detectors for the LHC proton-proton collider at CERN poses new challenges to the involved institutes regarding scientific, technological and organizational aspects of the process. In the case of the central vertex tracking systems, very complex assemblies have to be produced in large numbers and integrated into a device reliable enough to function for a planned experimental lifetime of at least ten years and in a radiation environment up to doses of several hundred kGy and fluences well above 1014 1MeV neutron equivalents/cm2 for the innermost parts of the tracking system. A quality assurance plan has to be implemented to ensure high quality of all parts according to the necessary performance parameters, define technical specifications accordingly and provide a good understanding of particle-detector interaction and the physical properties of the detector to extrapolate detector behaviour during the experiment. This thesis gives a detailed overview of the motivation, physics and organizational aspects and results of the quality assurance program for the silicon sensor used in the pixel subdetector for the ATLAS multi-purpose experiment. The sensor design used is shown to be well suitable for assembly and long term operation within the ATLAS experiment, and the quality plan implemented for sensor production has proven highly indicative for monitoring crucial aspects of sensor quality. In addition, problems within sensor production could be pinpointed at an early stage and further insights into the physical properties of sensors and parameters of their operation could be gained.2006-12-01T11:19:56ZDetermination of the Half Lives of Rare Decays of Cd, Te and Zn Isotopes for the COBRA ExperimentKiel, Henninghttp://hdl.handle.net/2003/215092015-08-12T20:40:32Z2005-07-05T09:26:36ZTitle: Determination of the Half Lives of Rare Decays of Cd, Te and Zn Isotopes for the COBRA Experiment
Authors: Kiel, Henning
Abstract: A search for rare decays of Cd, Te and Zn isotopes, especially double beta decays, within the COBRA experiment is presented. The measurements were made with a 2x2 array of 1 cm^3 CdZnTe semiconductor detectors which has been built in the R&D phase for a 4x4x4 prototype detector array.
For this prototype detector array a data acquisition system using the VME bus has been set up and programmed including a custom built VME-ADC which has been designed and tested. A detector simulation program based on GEANT4 has been developed which is used to calculate detection efficiencies and simulate various detector setups and signal as well as background events.
With a collected statistics of 2.9 kg*days for the two neutrino double beta decay of Cd116 a current sensitivity on the half life of about 10^17 years has been achieved. This value is only about two orders of magnitude away from the experimental half life value of 2.9*10^19 years for Cd116. The best sensitivities on the half life for neutrino-less double beta decay reach a lower half life limit of 10^20 years which corresponds to a sensitivity of 77.6 eV for the majorana neutrino mass each with 90% C.L. For some decay channels world best limits on the half life were set.
In addition to double beta decays the 4-fold forbidden non-unique beta decay of Cd113 has been investigated. The half life of this decay has been determined as
(8.2 +- 0.2(stat.)+0.2/-1.0(syst.))*10^15 years (90% C.L.). Furthermore, the spectral shape as recommended by the Table of Isotopes has been proven wrong. For the radiative electron decay a modest limit on the half life of >1.3*10^20 years could be set. The charge non-conserving decay of Cd113 to In113 and only neutrals has been investigated as well resulting in a lower limit on the half life 1.47*10^19 years which surpasses the best previous measurements on Cd113 by one order of magnitude.
As can be seen with this R&D setup already good results could be achieved. Performing extensive simulations with the Monte Carlo program developed in this thesis the currently dominating background source for double beta decay searches could be identified in form of the passivation paint on the detectors.2005-07-05T09:26:36ZATLAS Pixel Module - der Aufbau und deren Tests im Labor und im PionenstrahlMass, Martinhttp://hdl.handle.net/2003/201632015-08-13T00:33:51Z2005-02-17T00:00:00ZTitle: ATLAS Pixel Module - der Aufbau und deren Tests im Labor und im Pionenstrahl
Authors: Mass, Martin
Abstract: Der ATLAS-Pixeldetektor stellt den innersten der ATLAS-Subdetektoren dar und soll im ATLAS-Detektor für eine Laufzeit von 10 Jahren vom Vertex abgehende Teilchenspuren detektieren. Der Pixeldetektor besteht aus ca. 1700 hybriden Modulen, die für ihren Einsatz ein Höchstmaß an Zuverlässigkeit bieten müssen, da Wartungs- und Reperaturarbeiten nur einmal jährlich möglich sind.In Dortmund werden bis Ende 2005 vorraussichtlich ca. 250 dieser Module gefertigt und getestet werden. Zu diesem Zweck wurde an der Universität Dortmund eine Produktions- und Testlinie zur Herstellung und vollständigen Charakterisierungaufgebaut.Am H8-Teststrahl des SPS am CERN wurden bestrahlte und unbestrahlte Module mit einem 180 GeV Pionenstrahl getestet, um Aussagen über deren Eigenschaften nach der Strahlenbelastung von 10 Betriebsjahren im Inneren des ATLAS-Detektors treffen zu können.2005-02-17T00:00:00ZCharge collection in irradiated silicon detectorsKrasel, Olafhttp://hdl.handle.net/2003/23542015-08-13T02:31:31Z2004-08-10T00:00:00ZTitle: Charge collection in irradiated silicon detectors
Authors: Krasel, Olaf2004-08-10T00:00:00ZParticle production yields induced by multi-GeV protons on nuclear targetsGroßheim, Alexanderhttp://hdl.handle.net/2003/23532015-08-13T00:02:53Z2004-03-31T00:00:00ZTitle: Particle production yields induced by multi-GeV protons on nuclear targets
Authors: Großheim, Alexander
Abstract: In this study a first analysis is presented which extracts large-angle particle production rates from data taken by the HARP experiment. The analysis is carried out for nine different settings in order to compare the results in view of their dependence on the beam momentum and the target material. To achieve this goal, a fully-featured simulation for the relevant subdetector, the TPC, has been developed. This simulation was then used to unfold the measured momentum and angular distributions of secondaries. The unfolding scheme has been validated with simulated data. Due to the lack of particle identification at the time of this study, the results are not analysed in view of the best parameters for the target station of a Neutrino Factory. Nevertheless, the ratios and trends of the results presented here should already be reliable and have to be confirmed by future analyses. In addition, a comprehensive description of the HARP trigger and data acquisition system is given.2004-03-31T00:00:00ZEntwicklung und Evaluation eines realen-internetgesteuerten Experimentes für verschiedene AnfängerpraktikaBorowski, Andreashttp://hdl.handle.net/2003/23522015-08-13T00:03:06Z2004-02-04T00:00:00ZTitle: Entwicklung und Evaluation eines realen-internetgesteuerten Experimentes für verschiedene Anfängerpraktika
Authors: Borowski, Andreas2004-02-04T00:00:00ZCharacterisation of ionisation induced surface effects for the optimisation of silicon detectors for particle physics applicationsWüstenfeld, Jenshttp://hdl.handle.net/2003/23512015-08-12T16:53:27Z2001-11-12T00:00:00ZTitle: Characterisation of ionisation induced surface effects for the optimisation of silicon detectors for particle physics applications
Authors: Wüstenfeld, Jens2001-11-12T00:00:00ZDer ATLAS-PixelsensorHügging, Fabian Georghttp://hdl.handle.net/2003/23502015-08-12T16:40:53Z2001-10-31T00:00:00ZTitle: Der ATLAS-Pixelsensor
Authors: Hügging, Fabian Georg
Abstract: Das ATLAS Experiment soll ab 2006 Proton-Proton-Kollisionen am Large Hadron Collider (LHC) hochpräzise vermessen, um neue Erkenntnisse im Bereich der Teilchenphysik bei Schwerpunktenergien bis zu 1 TeV und mehr zu liefern. Die technologisch vielleicht anspruchsvollste Komponente des Experimentes stellt der Pixeldetektor dar, der nahe dem Wechselwirkungspunkt eine präzise Spurmessung der bei den Proton-Proton-Kollisionen erzeugten geladenen Elementarteilchen gewährleisten soll. Neben der hohen Wechselwirkungsrate von 40 MHz und der hohen Spurdichte stellt die enorme Strahlenbelastung von bis zu 1015 Teilchen pro Quadratzentimeter (1 MeV Neutron äquivalent), denen alle Komponenten des Pixeldetektor während der geplanten 10-jährigen Betriebszeit ausgesetzt sind, eine wesentliche Anforderung dar. Für den Pixeldetektor wurde ein hybrides Siliziumpixelkonzept gewählt, bei dem der Sensorbaustein und die Ausleseelektronik getrennt gebaut werden und erst in einem weiteren Verarbeitungsschritt (Bump-Bonding) miteinander verbunden werden. Gegenstand der vorliegendes Arbeit ist die Entwicklung des Sensorbausteins des ATLAS Pixeldetektors bis zur Produktionsreife. Die hohen Anforderungen führen dabei zu einem strahlungstoleranten Silizium-Pixelsensor, der bei mehreren hundert Volt und nur teilweise verarmt betrieben werden kann ohne auf eine homogene Ladungssammlung, kleine Pixelzellen oder dünne Sensoren zur Reduzierung der störenden Vielfachstreuung verzichten zu müssen. Weiterhin ist ein Punch-Througk-Biasnetzwerk implementiert worden, um realistische Tests der Pixelsensoren vor der Weiterverarbeitung zu ermöglichen. Die Übertragbarkeit der gewonnenen Erkenntnisse auf zukünftige Sensorentwicklungen auch außerhalb der Teilchenphysik werden diskutiert.2001-10-31T00:00:00ZAnalysis of neutrino interactions and search for neutral heavy particles with the front calorimeter of the NOMAD experimentGeppert, Dirkhttp://hdl.handle.net/2003/23492015-08-12T17:09:09Z2001-02-16T00:00:00ZTitle: Analysis of neutrino interactions and search for neutral heavy particles with the front calorimeter of the NOMAD experiment
Authors: Geppert, Dirk
Abstract: Der NOMAD-Detektor am CERN wurde für die Suche nach Tau-Neutrinos im CERN Breitband-Neutrino-Strahl, der hauptsächlich aus Myon-Neutrinos besteht, konzepiert. Neutrino-Wechselwirkungen im Front-Kalorimeter (FCAL) des Detektors der Datennahme-Perioden 1996-1998 wurden analysiert. Eine Suche nach schweren neutralen Leptonen (NHL) wurde durchgeführt, die in schwachen neutralen Myon-Neutrino Wechselwirkungen im FCAL-Target erzeugt werden und in Endzustände zerfallen, die ein Myon enthalten. Kein Anzeichen für die Existenz eines solchen Teilchen wurden gefunden. Die Ergebnisse wurden im Rahmen einer Theorie der Großen Vereinheitlichung (GUT) parametrisiert, in dem das schwere neutrale Lepton als Singulet unter der Gruppe des schwachen Isospins des Standard Models der Teilchenphysik vorhergesagt wird.; The NOMAD detector at CERN was designed for the appearance search of tau neutrinos in the CERN wide-band neutrino beam, predominantly composed of muon type neutrinos. Neutrino interactions in the front calorimeter (FCAL) of the detector accumulated during the 1996-1998 data taking periods have been analyzed. A search for muon type neutral heavy leptons (NHL) produced by neutral-current muon neutrino interactions in the FCAL target and decaying into final states including a muon has been conducted. No evidence for the existence of such a particle has been found. The results have been parametrized in terms of a Grand Unification Theory (GUT) NHL predicted to behave as a singlet under weak-isospin group of the Standard Model of particle physics.2001-02-16T00:00:00ZDreidimensionale Bauelementesimulationen verschiedener Prototyp-Designs für den ATLAS-PixelsensorBartsch, Valeriahttp://hdl.handle.net/2003/23482015-08-12T23:55:58Z2000-03-10T00:00:00ZTitle: Dreidimensionale Bauelementesimulationen verschiedener Prototyp-Designs für den ATLAS-Pixelsensor
Authors: Bartsch, Valeria
Abstract: Im Rahmen dieser Diplomarbeit sind die Pixelsensoren, die für das im Jahr 2005 geplante Hochenergieexperiment ATLAS (A Toroidal LHC Apparatus) am LHC (Large Hadron Collider) in Genf gebaut werden, mit Hilfe der Bauelementesimulation untersucht worden. Um die ATLAS Pixelsensoren wirklichkeitsgetreu zu simulieren, ist in dieser Diplomarbeit der Schritt von zweidimensionalen Simulationen zu dreidimensionalen Simulationen gemacht worden. In dieser Arbeit ist zunächst die GCD Struktur untersucht worden, um die Vorhersagekraft des verwendeten kommerziellen Programmpaketes ISE TCAD festzustellen. Darüberhinaus sind strahleninduzierte Veränderungen des Detektorverhaltens mit Hilfe von bekannten Defektniveaus, die durch DLTS und TSCMessungen bestimmt worden sind, erstmalig simuliert worden. Wegen des hohen Arbeitsspeicherbedarfs dreidimensionaler Simulationen ist die Oxidschicht durch ein geeignetes Modell, welches im Rahmen des Simulationspaketes einsetzbar ist, zu ersetzen und damit den benötigten Arbeitsspeicher zu reduzieren. Zwischen den drei im Rahmen dieser Diplomarbeit entwickelten Modellen ist eine klare Auswahl getroffen worden. Bei der dreidimensionalen Simulation der ATLAS Pixelsensor Prototypen konnten die Potentiale der floatenden Implantationen des Tile1Designs und des Tile3Designs bestimmt werden. Bei dem Vergleich mit zweidimensionalen Simulationen ist eine gute Übereinstimmung festgestellt worden. Insgesamt ist gezeigt worden, daß dreidimensionale Simulationen der ATLAS Pixelsensoren mit Hilfe des Programmpaketes ISE TCAD erfolgreich durchgeführt werden können. In Zukunft werden dreidimensionale Simulationen wegen der Weiterentwicklung der Computer sicherlich Standard werden. Die Arbeit ist die elektronische Version der Diplomarbeit Bartsch, Valeria: Dreidimensionale Bauelementesimulationen verschiedener Prototyp-Designs für den ATLAS-Pixelsensor".2000-03-10T00:00:00Z