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Hadronenstruktur und Fundamentale Symmetrien

Stephan Paul


Our group involved in a number of research projects dealing with high energy particle physics and neutron physics.


James-Franck-Str. 1/I
85748 Garching b. München
+49 89 289 12572
Fax: +49 89 289 12570

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Ausgeschriebene Angebote für Abschlussarbeiten an der Arbeitsgruppe

Double-sided silicon microstrip detectors for track reconstruction in COMPASS - implementation of clustering algorithms

The COMPASS collaboration operates at the CERN Super Proton Synchrotron a complex detector setup including silicon microstrip detectors for the observation of charged particles trajectories. Due to high beam intensity and reactions with several particles in the final state, many particles cross within the same time window, and the observed hit pattern must be analysed using elaborate clustering and background suppression algorithms. While after many years of running, the implemented algorithms have been refined and enhanced in several iterations, there is known room for improvement, and a need for working over the related software. Depending of the pre-knowledge for this bachelor thesis, this may be a well-defined part of it, or the overall structure (within the analysis C++ framework).

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Jan Michael Friedrich
Entwicklung eines autonomen Triggersystems mit Myonkammern mit zylindrischen Driftrohren.

Kammern mit zylindrischen Driftrohren sind bestens für die Instrumentierung großflächiger Myonsysteme von Hadroncolliderexperimenten geeignet. Sie gestatten es kostengünstig, die Flugbahnen der Myonen sehr genau zu vermessen. Bisher wurden diese Kammern stets zusammen mit schnellen Triggerkammern betrieben. Die Fortschritte im Bereich der Digitalelektronik, insbesondere die Verfügbarkeit leistungsfähiger FPGAs, eröffnen die Möglichkeit, Kammern mit zylindrischen Driftrohre selbstauslösend ohne schnelle Triggerkammern zu betreiben. In der Bachelorarbeit soll dies mit Hilfe simulierter und experimenteller Daten demonstriert werden.

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Oliver Kortner
Investigation of systematics of using an electromagnetic calorimeter for measuring a high-energy cross-section revealing pion dynamics

The TUM group of the COMPASS collaboration at the CERN Super Proton Synchroton specialized in the analysis of high-energy scattering reactions for a better understanding of the strong interaction and the quark-gluon structure of hadrons. The lightest hadron, the pion, consists mainly of light up- and down-quarks and has surprising properties linked to the breaking patterns of chiral symmetry. For the investigation of one of them, the chiral anomaly, a special scattering type has been examined with a charged and a neutral pion in the final state. The neutral pion decays almost promptly into two photons, which are observed in an electromagnetic calorimeter. The analysis of the data depends on a good understanding of this detection, and on the separation of background. In this thesis, the dependence of different background suppression scenarios is to be studied, supporting the analysis for understanding an important aspect of the subatomic structure of matter.

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Jan Michael Friedrich
Optimierung der Impulsformung der Signale zylindrischer Driftrohre für den Betrieb bei hohen Teilchenflüssen

Zylindrische Driftrohre sind bestens für die genaue Vermessung der Flugbahnen von Myonen in Colliderexperimenten geeignet. Bei zukünftigen Beschleunigerprojekten wie dem HL-LHC oder dem FCC-hh werden diese Myonkammern einem Untergrund von Gammaquanten ausgesetzt sein. Die von diesen Gammanquanten ausgelösten Signale führen bei hohen Untergrundraten zur Verschlechterung des Myonnachweises. Dieser Effekt kann durch geeignete Pulsformungstechniken minimiert werden. In der Bachelorarbeit sollen verschiedene Ansätze zur Pulsformung mit simulierten und experimentellen Daten verglichen werden.

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Oliver Kortner
Pion polarisability from COMPASS high-statistics data

The COMPASS collaboration operates a complex spectrometer setup in order to investigate reactions of high-energy pion and muon beams with various targets. Final states with a single photon produced along the scattering of the beam particle, with only tiny momentum transfer to the target, serve to determine the electromagnetic polarisabilities of the scattered particle. This is the most precise way of accessing the pion polarisability, which is an important fundamental quantity of the microcosmos. Data have been taken in the years 2009 and 2012, with low and high statistics, respectively. The existing analysis of the 2009 data is to be applied to the 2012 data, with some need for refining the methods due to the higher statistics. Main part of the work is programming in a C++ based framework, and handling large data sets on computer clusters.

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
Themensteller(in): Jan Michael Friedrich
Search for New Particles at the COMPASS Experiment

In nature, quarks and gluons cannot exist as free particles and are always confined into hadrons. Unfortunately, the equations of the strong interaction that governs the behavior of quarks and gluons cannot be directly solved at energy scales where hadrons form. Hence theoretical predictions of hadron properties like masses and decay modes are very difficult. This is in particular true for hadrons that are made of the three lightest quarks: „up“, „down“ and „strange“. Also on the experimental side much confusion exists on what concerns masses, decay widths, and the assignment of quantum numbers of some observed states, let alone the interpretation of their internal structure.

Our group participates in the COMPASS experiment at CERN, where we study the production of mesons (hadrons with integer spin) in the scattering of a 190 GeV pion beam off a stationary proton target. The produced highly excited mesons have extremely short life times of the order of 10-24 seconds and can hence be measured only via their decay products. Our group employs and develops mathematically involved analysis tools in order to identify the produced mesons with high sensitivity and to measure their properties with high precision. We have recently found a new meson with surprising properties and also did groundbreaking work on precision measurements of the properties of the pion. This science is directly connected to the understanding of the strong force at large distances and low energies and the search for new forms of matter and therefore addresses one of the last open questions of the Standard Model.

This science project, involves the use of several state-of-the-art technologies:

  • Building of analysis models in close collaboration with theorists
  • Handling of very large data sets (several Petabytes)
  • Elaborate data fitting with more than 1000 parameters
  • Use of large computing clusters (200 cores at E18 + 2000 cores at LRZ/Excellence cluster)
  • Software development to exploit new CPU/GPU technologies

In addition, we operate and maintain a large-scale scientific apparatus, which involves tasks like:

  • Calibration of particle detectors
  • Adaptation of large simulation codes

We offer thesis topics at various levels of difficulty, which cover a wide range of subjects in strong-interaction physics, statistics and/or computer science. They include for example

  • Data handling and event selection
  • Simulation of high-energy scattering processes and detector response
  • Model building and model selection
  • Estimation of model parameters from high-dimensional data
  • Parallelization of analysis software

You have the opportunity to perform your own science analysis, e.g. searching for new particles and determining their properties. The analysis work can start at different levels within the analysis chain: from the selection of a reaction process itself in order to study the feasibility of a full-fletched analysis up to the final fitting process leading to scientific publications. The topic can be chosen according to personal preference and interest. Thesis projects usually involve travels to CERN.

Experience in programming (C++, Python) is helpful, but not required.

Contact: Boris Grube, room PH1 3574, Tel. 089 289 12588