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Dark Matter

Prof. Susanne Mertens

Research Field

We study the elusive particle, the neutrino, to unlock fundamental mysteries of physics: What is our universe made of? How did structures evolve? Why is our world made of matter and not anti-matter?

Despite major discoveries in the last decades, the neutrino is still one of the most mysterious particles of the standard model of particle physics: What is its mass? Is it its own antiparticle? Does there exist a right-handed partner to the known left-handed neutrino, a so called sterile neutrino? Exploring these properties will help us understand fundamental open questions about our universe.

The Karlsruhe Tritium Neutrino (KATRIN) Experiment will directly measure the absolute neutrino mass. The knowledge of the neutrino mass will have a crucial impact on understanding the structure formation in the early universe. KATRIN is situated at the KIT in Karlsruhe and will start data taking in 2017. With an upgraded multi pixel Si-detector system, called TRISTAN, KATRIN can extend its physics goal to also search for keV-scale sterile neutrinos. This new neutrino species is an ideal candidate for Dark Matter. Our group is leading the sterile neutrino search with KATRIN

Besides KATRIN, our group is involved in the search for neutrinoless double beta decay (0nbb) with the MAJORANA experiment. The discovery of this process would proof that the neutrino is its own antiparticle, which in turn can help us understand the matter anti-matter asymmetry of the universe. MAJORANA and the closely related experiment GERDA plan to join in the near future to perform the ultimate search for this ultra-rare decay.

Address/Contact

Föhringer Ring 6
80805 München
susanne.mertens@tum.de
+49 89 32354-590

Members of the Research Group

Professor

Scientists

Teaching

Course with Participations of Group Members

Offers for Theses in the Group

Characterization of the next-generation TRISTAN prototype detector

Scientific motivation: 

Does there exist an undiscovered type of neutrino, a so-called sterile neutrino? Could this particle be the Dark Matter? These are among the most topical open questions in Astroparticle physics at the moment. 

The aim of the TRISTAN project, is to develop a novel multi-pixel Silicon Drift Detector system to upgrade the KATRIN apparatus. This upgrade would allow the  KATRIN experiment to search for this hypothetical new particle. 


Thesis Topic:

The topic of this Thesis project is the characterization of the next-generation TRISTAN prototype detectors. The goal of this project is a detailed understanding of the detector response to photons and electrons. For this purpose you will perform measurements with x-ray calibration sources and with an electron microscope at the Semiconductor Laboratory of the Max Planck society in Munich. For this purpose a dedicated test stand has to be designed and fabricated. The measurements and data analysis will be complemented with detailed Monte Carlo simulations of the particle interactions in the detector and the signal generation. 


You will gain & learn:

  • Learn about astroparticle physics 

  • Detailed understanding of semiconductor detector technology

  • Expertise in experimental hardware work 

  • Programming in Python and C++

  • Work in a fun team with lots of social events

suitable as
  • Master’s Thesis Nuclear, Particle, and Astrophysics
Supervisor: Susanne Mertens
ComPol - a Compton telescope inside a nano satellite

Scientific motivation:

The structure of astrophysical compact objects e.g. black hole binaries (BHB) can not be resolved with optical methods. Therefore one has to use other methods to get informations on processes in and around these systems. By measuring the polarization of the emitted hard X-rays it is possible to draw conclusions on their production mechanism and the geometrical structure of BHBs. The CubeSat project ComPol (Compton Polarimeter) aims at measuring spectrum and polarization of the BHB Cygnus X-1 in the hard X-ray range (20 - 2000 keV).

Since it will be a CubeSat based mission, the whole system has to be very compact to fit in the satellites volume (~10x10x30cm³). The small detector area together with strong weight limitations makes it ambitious to achieve a good sensitivity. Besides lab tests simulations are needed to get the best out if it.


Thesis Topics:

  1. Simulation based design study for ComPol, a Compton telescope inside a Nano-satellite

  2. Characterizing and testing components of the first ComPol prototype

 

You will gain & learn:

  • Learn about astroparticle physics

  • Understand the working principle of Compton telescopes

  • Detailed understanding of semiconductor detector technology

  • Expertise in experimental hardware work

  • Knowledge of Monte Carlo particle simulation with Geant4

  • Programming in Python and C++

  • Work in a fun team with lots of social events

suitable as
  • Master’s Thesis Nuclear, Particle, and Astrophysics
Supervisor: Susanne Mertens
Data analysis for the KATRIN experiment

Scientific motivation: 

What is the mass of the neutrino? This is one of the most fundamental open questions in Astroparticle Physics today. We know from neutrino oscillations that neutrinos must have a mass, but its actual value is still unknown. The knowledge of the neutrino mass would be an important key to understand the formation of structures in the early universe and it could help to shed light on the fundamental origin of masses.

The Karlsruhe Tritium Neutrino (KATRIN) experiment is a direct neutrino mass experiment, which is designed to determine the neutrino mass via a precise measurement of the tritium beta decay spectrum. KATRIN just started data taking in April 2019. The goal is to reach a sensitivity to the neutrino mass of 200 meV after 3 years of data taking. So, right now is the perfect moment to join the experiment!


Thesis Topic: In this Thesis project you participate in the analysis of the KATRIN data. You will analyze new data sets, acquired in the near future, which will provide unprecedented sensitivity to the neutrino mass. Besides using existing techniques we also focus on developing novel analysis tools based on Bayesian techniques and neural networks. Finally, you will gain a deep understanding of the experiments, as systematic uncertainties in the theoretical description of the measured beta-decay spectrum are of key relevance to achieve the desired sensitivity. 


You will gain & learn: 

  • Participate in world-leading experiment to directly determine the neutrino mass

  • Learn about astroparticle physics 

  • In-depth knowledge on data analysis

  • Programming in C++ and Python

  • Work in a fun team with lots of social events

suitable as
  • Master’s Thesis Nuclear, Particle, and Astrophysics
Supervisor: Susanne Mertens
Detector R&D and data analysis with the LEGEND experiment

Motivation:

The observation of neutrinoless double beta (0𝜈ββ) decay would establish the Majorana nature of neutrinos and explicitly show that lepton number conservation is violated. In their search for the rare decay in the isotope Ge-76, the GERDA and Majorana Demonstrator experiments have achieved the lowest backgrounds and best energy resolutions of any 0𝜈ββ decay experiment. Building on the successful results of these experiments, the Large Enriched Germanium Experiment for Neutrinoless Double Beta Decay (LEGEND) collaboration aims to develop a phased 0𝜈ββ decay experimental program. The first phase of LEGEND, a 200 kg measurement utilizing the existing GERDA infrastructure at LNGS in Italy, is expected to start in 2021. Be part of this amazing collaboration with about 200 scientists from all over the world.


Thesis topics:

  1. Development and characterization of ASIC-based readout electronics for Germanium detectors (with possibility of research stay at Berkeley lab)

  2. Analysis of first LEGEND data (e.g. focus on optimization of energy resolution)

  3. Pulse shape simulations (e.g. investigation of impact of diffusion and self-repulsion)


Technical skills and scientific environment:

  • Data analysis methods in experimental physics, C++ and Python programming

  • Electronics and cryogenics (liquid Argon & Nitrogen)

  • Astroparticle physics

  • Scientific writing and presentation of scientific results

Scientific supervision:

  • Prof. Dr. Susanne Mertens

  • Dr. Michael Willers (Postdoc)

suitable as
  • Master’s Thesis Nuclear, Particle, and Astrophysics
Supervisor: Susanne Mertens
Development of a theoretical model for the keV sterile neutrino search

Scientific motivation: 

Does there exist an undiscovered type of neutrino, a so-called sterile neutrino? Could this particle be the Dark Matter? These are among the most topical open questions in Astroparticle physics at the moment. 

The aim of the TRISTAN project, is to develop a novel multi-pixel Silicon Drift Detector system to upgrade the KATRIN apparatus. This upgrade would allow the  KATRIN experiment to search for this hypothetical new particle. 


Thesis Topic:

To search for keV sterile neutrinos in the differential energy spectrum of tritium a sophisticated model is required, which will be the main aspect of this Thesis topic. You will develop and extend the existing model used in the KATRIN experiment for the neutrino mass measurement, to suite the keV sterile neutrino search. A key aspect of this investigation is the understanding of systematic uncertainties and their impact on the final sensitivity of the final TRISTAN experiment. Additionally, already now we can extract an differential energy spectrum from the ongoing measurements through the Forward Beam Monitor, where you can test your model and may extend the current limits for keV sterile neutrinos.


You will gain & learn:

  • Learn about astroparticle physics 

  • In-depth knowledge on data analysis

  • Programming in Python and C++

  • Work in a fun team with lots of social events

suitable as
  • Master’s Thesis Nuclear, Particle, and Astrophysics
Supervisor: Susanne Mertens
Simulation and analysis of backgrounds for the Solar Axion Experiment IAXO

Scientific motivation: 

Axions are a well motivated explanation for the strong CP problem. They are also one of the most promising Dark Matter candidate. The IAXO experiment is exploring a unique phase space to look for this particle emitted by the Sun. A very intense magnetic field would transform these solar axions into few keV x-rays. Silicon Drift Detectors (SDD) are a very suitable candidate for x-ray detection. The background of such a detector is the only limiting factor. Therefore it should be correctly measured, understood and mitigated.


Thesis Topics:

 The thesis would focus on measuring with the existing set-up located at the TUM UGL the SDD intrinsic background as well as to model its provenance. Then depending on this result, work would be to design a new detector/set-up to reach the final IAXO requirements. 


You will gain & learn:

  • Learn about astroparticle physics 

  • Detailed understanding of semiconductor detector technology

  • Expertise in experimental hardware work and simulations

  • Programming in Python and C++

  • Low background in the keV regime 

  • Work in a fun team with lots of social events

suitable as
  • Master’s Thesis Nuclear, Particle, and Astrophysics
Supervisor: Susanne Mertens

Current and Finished Theses in the Group

Energy Calibration of the TRISTAN Silicon Drift Detectors
Abschlussarbeit im Bachelorstudiengang Physik
Themensteller(in): Susanne Mertens
Pulse Shape Analysis with the TRISTAN Silicon Drift Detector
Abschlussarbeit im Bachelorstudiengang Physik
Themensteller(in): Susanne Mertens
Investigation of the noise performance of silicon drift detectors for the TRISTAN project
Abschlussarbeit im Bachelorstudiengang Physik
Themensteller(in): Susanne Mertens
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