Stuttgart, Univ., Diss., 2007.

Universiẗat, Diss., 2002--München.

Techn. Hochsch., Diss., 2000--Aachen. / Gedr. Ausg. im Physikalischen Inst., Aachen.

Universiẗat, Diss., 2001--Dortmund.

Techn. Hochsch., Diss., 2002--Aachen.

Techn. Hochsch., Diss., 1997--Aachen.

Freiburg i. Br., Univ., Diss., 2008.

In the United States, educators have struggled with low student achievement in reading proficiency, which affects student success in school and leads to higher dropout rates. To address low reading proficiency scores, a local charter high school implemented the myON'reader program. The myON reader program is an electronic library that allows students to choose their own reading based on their reading level and interest. The program tracks students' reading habits and level of reading, so teachers can determine students' progress. Guided by self-directed learning and social constructivism, the purpose of this study was to review available data to determine if the program increased students' reading assessment scores. This study used a mixed-methods design and 3 sets of data: a reading assessment (n = 39), the myON'reader program itself (n = 39), and a semi-structured interview (n = 2). A paired-samples t test determined a statistically significant difference between pretest and posttest data in assessments of students using the myON'reader program. Pearson's correlation coefficient determined a statistically significant correlation between the difference in the reading test scores and hours the students read, as well as a statistically significant correlation between reading test scores and Lexile level of reading. Finally, a semi-structured interview was conducted to determine the teachers' opinions of the program providing additional data for triangulation. The interview was recorded, transcribed, and coded to determine common themes. The positive social change implications included the improvement of student reading ability at the local charter high school, which over time will develop students better prepared for success.

Freiburg i. Br., Univ., Diss., 2007.

COMET ist ein zukunftsweisendes Experiment der neuen Generation. Es wird nach dem kohärenten neutrinolosen Übergang eines Myons zu einem Elektron im Coulombfeld eines Aluminiumatomkerns suchen. Dieser Prozess eröffnet herausragende Möglichkeiten zur Erforschung und Entdeckung neuer Physik, da die kohärente Myonen-zu-Elektronen Umwandlung die geladene Leptonenzahlerhaltung verletzt und im Standardmodell der Teilchenphysik bis weit unterhalb messbarer Beiträge unterdrückt ist. Das Experiment befindet sich derzeit in der Aufbauphase. In Phase-I wird angestrebt, das bestehende Limit auf das Verzweigungsverhältnis von 7x10^-13 um zwei Größenordnungen zu verbessern, wobei eine zusätzliche Verbesserung um mindestens zwei weitere Größenordnungen für Phase-II erwartet wird. Zur Realisierung dieser beeindruckenden Verbesserung benötigt das COMET-Experiment einen äußerst intensiven, niederenergetischen Myonenstrahl. Über die geplante Laufzeit des Experiments von 146 Tagen erreichen etwa 1,6x10^17 Myonen den Detektorbereich. Allerdings kann nur ein Bruchteil dieser Myonen genutzt werden, da diese zuerst gestoppt und an einen Atomkern gebunden werden müssen, bevor eine kohärente Umwandlung in Elektronen möglich ist. Diese Arbeit widmet sich der detaillierten Untersuchung der Komponente, die für diese Aufgabe verantwortlich ist: dem sogenannten Myonen-Stop Target. Mithilfe modernster Simulationstechnik werden die Parameter des Myonen-Stop Targets analysiert und optimiert, um die Anzahl der gestoppten Myonen zu maximieren, während gleichzeitig eine hohe Akzeptanz für die Signal-Elektronen gewährleistet wird. Darüber hinaus wird das Vorhaben untersucht, die Anzahl der gestoppten Myonen durch die Messung von charakteristischen myonischen Röntgenstrahlen mittels eines hochreinen Germaniumdetektors zu bestimmen. Es wird gezeigt, dass die 'Single Event Sensitivity' des Experiments um einen Faktor zwei auf bis zu 1,5x10^-15 verbessert werden kann, wenn ein Myonen-Stop Target verwendet wird, das aus 66 Aluminiumscheiben mit einer Dicke von 0,1mm besteht. Es wird eine spezielle Aufhängestruktur zur Befestigung dieser Scheiben entworfen und mithilfe eines entwickelten Prototyps umfangreich getestet. Installations- und Stabilitätstests zeigen eine Positionsgenauigkeit von +-1mm in x- und +-5mm in y- und z-Richtung. Innerhalb dieser Genauigkeit wird keine negative Auswirkung auf die Anzahl der gestoppten Myonen erwartet. Die Aufhängestruktur wurde auf Stabilität optimiert, wobei der Verlust an Signalakzeptanz durch Interferenz mit Signalelektronen auf 3,4% begrenzt werden konnte. Die Umsetzbarkeit des myonischen Röntgendetektors wird demonstriert. Die Platzierung des Detektors in einem Abstand von 6m und einem Winkel von 8,5° relativ zum Myonen-Stop Target, zusammen mit einer eigens entwickelten Detektorabschirmung, die ein 2m langes Kollimatorrohr mit einem Durchmesser von 50mm enthält, ist ausreichend, um die Untergrundrate im Germaniumdetektor auf ein arbeitsfähiges Niveau zu senken.:Kurzfassung Abstract List of Tables List of Figures 1. Introduction to Muons 1.1. Muons in the Standard Model 1.1.1. The Free Muon Decay and Flavour Conservation 1.1.2. Muonic Atoms 1.2. Muons in Beyond Standard Model Physics 1.2.1. Motivation behind (Charged) Lepton Flavour Violation 2. The COMET Experiment 2.1. A Staged Approach: COMET Phase-I and Phase-II 2.2. The μ−e Conversion Signal 2.2.1. Detecting Conversion Electrons: A Cylindrical Detector System 2.2.2. The Single Event Sensitivity 2.3. Understanding and Suppressing Background 2.3.1. Primary Beam: Proton Target, Energy, and Timing Structure 2.3.2. Particle Transport: Particle Selection with Bent Solenoids 2.3.3. Muon-Stopping Target: Shape and Material 3. The COMET Simulation: ICEDUST 3.1. Simulating the Primary Beam 3.2. Direct Simulation of Conversion Electrons and X-rays 3.3. Details of the Geometry and Magnetic Field 3.4. Handling of Physics in ICEDUST 3.5. General Optimization Strategy 4. The Muon-Stopping Target 4.1. Introduction: Status Quo and Motivation 4.2. Methodology 4.2.1. Interpreting Plots: The Centered Coordinate System 4.2.2. Investigating the Number of Muons Stopped 4.2.3. Investigating the Signal Acceptance 4.2.4. Investigating Detector Background Rates 4.2.5. Treatment of Uncertanties 4.3. Performance Overview: Default Configuration 4.3.1. Additional Information: Single Layer Occupancy 4.4. Starting Point: The Tube-like Disk Structure 4.4.1. Matching the Target Shape to the Beam Profile 4.4.2. Using Multiple Separate Target-Disks Forming a Tube 4.5. Changing the Target-Disk Radius 4.5.1. The Effect on Total Number of Muons Stopped 4.5.2. The Effect on Signal Acceptance 4.5.3. The Effect on Detector Background 4.5.4. Summary and Performance Overview 4.6. Material Budget: Target-Disk Thickness 4.6.1. Summary and Performance Overview 4.7. Material Budget: Total Number of Target-Disks 4.7.1. The Effect on Total Number of Muons Stopped 4.7.2. The Effect on Signal Acceptance 4.7.3. The Effect on Detector Background 4.7.4. Summary and Performance Overview 4.8. Disk Positioning Along the Beam Axis 4.9. Signal Background from Muon Decay In Orbit 4.9.1. Updated Results for the Default Configuration 4.9.2. Results for New Configurations 4.9.3. DIO Background from Other Isotopes 4.9.4. DIO Background from the Surrounding Helium Gas 4.10. Single Event Sensitivity for New Configurations 4.10.1. Calculating the SES 4.10.2. Summary and Interim Results 4.11. Production of Target-Disks 5. The Muon-Stopping Target Suspension 5.1. Technical Layout of the Suspension Structure 5.1.1. The Outer Ring Structure 5.1.2. The Three Long Bars 5.1.3. The Support Ring 5.2. Holding the Target-Disks in Place: The Spokes 5.3. The Installation Procedure 5.4. ICEDUST Study of Key Parameters 5.4.1. Positional Accuracy 5.4.2. Size of the Three Long Bars 5.5. Final Results and Summary 6. The Muon-Stopping Monitor 6.1. Methodology: The Two Main Parameters 6.1.1. Assessing the Germanium Detector Background 6.1.2. Calculating the Germanium Detector Signal Acceptance 6.2. Results: Positioning and Collimator 6.3. Discussion and Outlook 6.3.1. Moving Toward a Realistic Shielding 6.3.2. HPGe Data Acquisition: Read-out and Dead Time 6.3.3. Estimation of Accuracy 6.3.4. COMETs Timing Structure and Supplementary Measurements 7. Conclusion List of Acronyms References A. Collimator Performances / COMET is a next-generation experiment. It will search for the coherent neutrinoless transition of a muon to an electron in the Coulomb field of an atomic aluminium nucleus. This process provides a golden channel for probing and discovering new physics since coherent muon-to-electron conversion violates charged lepton flavor conservation and is suppressed below measurable contributions in the Standard Model of particle physics. During Phase-I, the experiment currently under construction seeks to improve the existing branching ratio limit of 7x10^-13 by two orders of magnitude, with an additional improvement by at least two orders of magnitude anticipated for Phase-II. To realize such remarkable improvements, the COMET experiment requires an incredibly intense, low-energy muon beam. Over a planned runtime of 146 days, approximately 1.6x10^17 muons will reach the detector area. However, only a fraction of these muons are usable, as they must first be stopped and bound to a nucleus to undergo conversion. Within this thesis, the component responsible for this task is under detailed scrutiny: the muon-stopping target. A simulation-based study evaluates and optimizes the muon-stopping target's parameters to maximize the number of stopped muons while maintaining a high acceptance for signal conversion electrons. In addition, the scheme to monitor the number of stopped muons by measuring muonic X-rays with a high-purity germanium detector is investigated. A twofold improvement in single event sensitivity to 1.5x10^-15 is shown to be achievable by employing 66 target-disks with a thickness of 0.1mm. A dedicated suspension structure to hold these target-disks is designed, prototyped, and tested. Installation and stability tests demonstrate a positional accuracy of +-1mm in x and +-5mm in y and z directions. Within this accuracy, no negative impact on the number of muons stopped is foreseen. The suspension structure is optimized for stability while limiting the decrease in signal acceptance from interference with signal electrons to 3.4%. The feasibility of the muonic X-ray detector is demonstrated. Placing the detector 6m away at an 8.5° angle relative to the muon-stopping target, along with dedicated shielding and a 2m long, 50mm diameter tube collimator, is sufficient to achieve workable background rates for the high-purity germanium detector.:Kurzfassung Abstract List of Tables List of Figures 1. Introduction to Muons 1.1. Muons in the Standard Model 1.1.1. The Free Muon Decay and Flavour Conservation 1.1.2. Muonic Atoms 1.2. Muons in Beyond Standard Model Physics 1.2.1. Motivation behind (Charged) Lepton Flavour Violation 2. The COMET Experiment 2.1. A Staged Approach: COMET Phase-I and Phase-II 2.2. The μ−e Conversion Signal 2.2.1. Detecting Conversion Electrons: A Cylindrical Detector System 2.2.2. The Single Event Sensitivity 2.3. Understanding and Suppressing Background 2.3.1. Primary Beam: Proton Target, Energy, and Timing Structure 2.3.2. Particle Transport: Particle Selection with Bent Solenoids 2.3.3. Muon-Stopping Target: Shape and Material 3. The COMET Simulation: ICEDUST 3.1. Simulating the Primary Beam 3.2. Direct Simulation of Conversion Electrons and X-rays 3.3. Details of the Geometry and Magnetic Field 3.4. Handling of Physics in ICEDUST 3.5. General Optimization Strategy 4. The Muon-Stopping Target 4.1. Introduction: Status Quo and Motivation 4.2. Methodology 4.2.1. Interpreting Plots: The Centered Coordinate System 4.2.2. Investigating the Number of Muons Stopped 4.2.3. Investigating the Signal Acceptance 4.2.4. Investigating Detector Background Rates 4.2.5. Treatment of Uncertanties 4.3. Performance Overview: Default Configuration 4.3.1. Additional Information: Single Layer Occupancy 4.4. Starting Point: The Tube-like Disk Structure 4.4.1. Matching the Target Shape to the Beam Profile 4.4.2. Using Multiple Separate Target-Disks Forming a Tube 4.5. Changing the Target-Disk Radius 4.5.1. The Effect on Total Number of Muons Stopped 4.5.2. The Effect on Signal Acceptance 4.5.3. The Effect on Detector Background 4.5.4. Summary and Performance Overview 4.6. Material Budget: Target-Disk Thickness 4.6.1. Summary and Performance Overview 4.7. Material Budget: Total Number of Target-Disks 4.7.1. The Effect on Total Number of Muons Stopped 4.7.2. The Effect on Signal Acceptance 4.7.3. The Effect on Detector Background 4.7.4. Summary and Performance Overview 4.8. Disk Positioning Along the Beam Axis 4.9. Signal Background from Muon Decay In Orbit 4.9.1. Updated Results for the Default Configuration 4.9.2. Results for New Configurations 4.9.3. DIO Background from Other Isotopes 4.9.4. DIO Background from the Surrounding Helium Gas 4.10. Single Event Sensitivity for New Configurations 4.10.1. Calculating the SES 4.10.2. Summary and Interim Results 4.11. Production of Target-Disks 5. The Muon-Stopping Target Suspension 5.1. Technical Layout of the Suspension Structure 5.1.1. The Outer Ring Structure 5.1.2. The Three Long Bars 5.1.3. The Support Ring 5.2. Holding the Target-Disks in Place: The Spokes 5.3. The Installation Procedure 5.4. ICEDUST Study of Key Parameters 5.4.1. Positional Accuracy 5.4.2. Size of the Three Long Bars 5.5. Final Results and Summary 6. The Muon-Stopping Monitor 6.1. Methodology: The Two Main Parameters 6.1.1. Assessing the Germanium Detector Background 6.1.2. Calculating the Germanium Detector Signal Acceptance 6.2. Results: Positioning and Collimator 6.3. Discussion and Outlook 6.3.1. Moving Toward a Realistic Shielding 6.3.2. HPGe Data Acquisition: Read-out and Dead Time 6.3.3. Estimation of Accuracy 6.3.4. COMETs Timing Structure and Supplementary Measurements 7. Conclusion List of Acronyms References A. Collimator Performances