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Hadronic Structure and Fundamental Symmetries

Prof. Stephan Paul

Research Field

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

Address/Contact

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

Members of the Research Group

Professor

Office

Scientists

Students

Other Staff

Teaching

Course with Participations of Group Members

Offers for Theses in the Group

Build up of a 4He purifier

Outline, calculation and design of a purification cryostat to produce isotopically pure He-4 out of natural helium in a continuous manner based on the superfluid heat flush principle.

The FRM II is presently testing and will subsequently install a source to produce ultra-cold neutrons (UCN) in the reactor. In the central section of this UCN source, helium is used for cooling. By passing through, the cooling agent helium will be irradiated by neutrons, which create radioactive tritium out of the He-3 portion. This negative side effect can be avoided respectively reduced to a permissible level if isotopically purified He-4 with no traceable He-3 content is used.

Sources for isotopically pure He-4 are scarce and availability varies with market demand. In order to ensure continuous operation of the UCN source the availability must be secured. For this reason such an isotopic purifier shall be build.

In this thesis a small illustrator shall be build up, and its cool down characteristics shall be measured.

Contact / Supervisor:

Dr. Andreas Frei, Tel. 089 289 14260, andreas.frei@tum.de

suitable as
  • Bachelor’s Thesis Physics
Supervisor: Stephan Paul
Outline, calculation and design of a purification cryostat to produce isotopically pure He-4 out of natural helium in a continuous manner based on the superfluid heat flush principle.

The FRM II is presently testing and will subsequently install a source to produce ultra-cold neutrons (UCN) in the reactor. In the central section of this UCN source, helium is used for cooling. By passing through, the cooling agent helium will be irradiated by neutrons, which create radioactive tritium out of the He-3 portion. This negative side effect can be avoided respectively reduced to a permissible level if isotopically purified He-4 with no traceable He-3 content is used.

Sources for isotopically pure He-4 are scarce and availability varies with market demand. In order to ensure continuous operation of the UCN source the availability must be secured. For this reason such an isotopic purifier shall be build.

In the first phase a smaller illustrator shall be designed and made to prove feasibility and validate the concept. The above master thesis is part to this first phase.

In a second phase a scaled-up apparatus shall be manufactured for operational use.

Contact / Supervisor:

Dr. Andreas Frei, Tel. 089 289 14260, andreas.frei@tum.de

suitable as
  • Master’s Thesis Nuclear, Particle, and Astrophysics
  • Master’s Thesis Applied and Engineering Physics
Supervisor: Stephan Paul
Measurement of the scattering cross section of ultracold neutrons on solid ortho-deuterium (o-D2) at a temperature of T = 5 K

Mit Hilfe von Streuexperimenten von ultrakalten Neutronen (UCN) an Kryo-Festkörpern bestimmen Sie Wechselwirkungsquerschnitte bei niedrigsten Energien. Des Weiteren beschäftigen Sie sich mit verschiedenen Aspekten der Erzeugung von ultrakalten Neutronen mittels superthermischer Konversion im Rahmen des Aufbaus der Quelle für ultrakalte Neutronen am FRM II. Ihre experimentell gewonnenen Ergebnisse bewerten Sie im Hinblick auf Auslegung und Verbesserung von neuartigen Quellen für sehr kalte und ultrakalte Neutronen. Ihr Experiment führen Sie am Forschungsreaktor des Institut Laue-Langevin (ILL) in Grenoble durch.

suitable as
  • Master’s Thesis Condensed Matter Physics
  • Master’s Thesis Nuclear, Particle, and Astrophysics
  • Master’s Thesis Applied and Engineering Physics
Supervisor: Stephan Paul
Search for New Particles at the COMPASS Experiment at CERN

In nature, quarks and gluons cannot exist as free particles. They 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 such as their 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 hadrons, 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 statistical 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
  • Estimation of model parameters from high-dimensional data
  • Model building and model selection
  • 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

suitable as
  • Master’s Thesis Nuclear, Particle, and Astrophysics
Supervisor: Stephan Paul
Search for New Particles at the COMPASS Experiment at CERN

In nature, quarks and gluons cannot exist as free particles. They 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 such as their 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 hadrons, 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 statistical 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 addresses one of the last open questions of the Standard Model of particle physics, which is the understanding of the strong force at large distances and low energies.

We offer thesis topics, which cover a wide range of subjects in strong-interaction physics, statistics, and/or computer science. The thesis work can start at different levels within the analysis chain: from the selection of a reaction process itself up to the final fitting process leading to scientific publications. The topic can be chosen according to personal preference and interest.

Experience in computer programming is helpful, but not required.

Contact: Boris Grube bgrube@tum.de, room PH1 3574, Tel. 089 289 12588

suitable as
  • Bachelor’s Thesis Physics
Supervisor: Stephan Paul
Simualtion of an 4He Purifier with COMSOL

Outline, calculation and design of a purification cryostat to produce isotopically pure He-4 out of natural helium in a continuous manner based on the superfluid heat flush principle.

The FRM II is presently testing and will subsequently install a source to produce ultra-cold neutrons (UCN) in the reactor. In the central section of this UCN source, helium is used for cooling. By passing through, the cooling agent helium will be irradiated by neutrons, which create radioactive tritium out of the He-3 portion. This negative side effect can be avoided respectively reduced to a permissible level if isotopically purified He-4 with no traceable He-3 content is used.

Sources for isotopically pure He-4 are scarce and availability varies with market demand. In order to ensure continuous operation of the UCN source the availability must be secured. For this reason such an isotopic purifier shall be build.

In this thesis the thermodynamical properties of the purifier shall be simulated with COMSOL.

Contact / Supervisor:

Dr. Andreas Frei, Tel. 089 289 14260, andreas.frei@tum.de

suitable as
  • Bachelor’s Thesis Physics
Supervisor: Stephan Paul

Current and Finished Theses in the Group

Search for New Particles at the COMPASS Experiment at CERN
Abschlussarbeit im Masterstudiengang Physik (Kern-, Teilchen- und Astrophysik)
Themensteller(in): Stephan Paul
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