Theses Topics
Possible topics for Bachelor and Master theses in our research group reach from developing, testing and building detectors to the development of analysis and simulation software for the presently running CBELSA/TAPS experiment and the future PANDA experiment. In addition, further data analysis topics are offered within the CBELSA/TAPS experiment.
If you are interested in a Bachelor or Master thesis within one of our research projects, please do not hesitate to contact us. A few examples for possible topics are listed below.
Examples for Master-thesis subjects
Crystal Barrel/TAPS Experiment
Study of timing capabilities of the CB SADC
CB Sampling ADCs (SADC) will be installed for all crystals of the calorimeter within the next month. First SADC-data from the Crystal Barrel Calorimeter has already been recorded and analyzed. At the time of this measurement only the forward rings of the calorimeter had been equipped with SADCs allowing for detailed tests. A working firmware for the SADC's FGPA (field programmable gate array - the core of the SADC) allows the extraction of the basic "features" (energy, timing) and also a pile-up recognition. The timing capabilities are however limited due to a non-ideal synchronization of the trigger signal, and a constant fraction discrimination (CFD) with limited accuracy and room for parameter optimization. Within this thesis, the determination of the trigger timestamp as well as the CFD timestamp should be optimized, with a goal to reach a standard deviation of less than 40ns for small pulses. This is achieved in four steps:
- Optimization of the algorithms in VHDL
- Verification of the current and improved performance with a VHDL testbench (simulation of the FPGA's firmware) or SIMULINK
- Verification of the current and improved performance with a lab setup
- Verification during a beam-time at ELSA (if possible)
Simulations, Design and setup of a new Møller detector
To monitor the polarization of electrons, Møller scattering can be used. Within this thesis an upgrade of the present Møller detector is planned. The thesis includes simulation of the Møller process, the design of the detector, as well as its setup.
Improving the kinematic fit of the Crystal Barrel / TAPS- Experiment
All measured quantities, such as e.g. the energies and angles of the photons measured in the Crystal Barrel / TAPS- experiment have uncertainties. Now, a kinematic fit makes use of conservation laws such as energy- and momentum-conservation or the known particle masses to vary the measured quantities within their known uncertainties. This allows for improvements in the resolution as well as for a measure of how well a certain event matches a certain hypotheses in the fit (e.g. γp→ pπ°π° to p4γ in comparison to γp→ pπ°η to p4γ).
To do so the uncertainties of the measured values need to be well known and should ideally show a Gaussian distribution. This is unfortunately quite often only approximately the case. The aim of this Master thesis is an improvement of the existing kinematic fit extending also its present functionality. It is e.g. planned to add the option to fit the vertex in the target, where the particles are produced. New functionalities should go along with an improvement of the exiting software structure and code.
Simulation and reconstruction of cosmics in the TAPS detector
Presently a pre-calibration of the TAPS detector is performed by considering muons traveling through the TAPS crystals of the detector system. Within this thesis it is planned to use the Cosmic-ray Shower Library of the Lawrence Livermore National Laboratory to simulate cosmics considering properly their angular and energy distributions. Tracking the particles with Geant through the detector system, a realistic simulation of cosmics in the TAPS detector can be performed.
After reconstruction, the expected energy deposits in the different crystals depending on their event topology can be determined as well as in the respective scintillators in front of the crystals. The simulated distributions can be compared to the ones obtained in experiment. This will lead to an improved energy-precalibration for the crystals as well as to an energy-calibration for the vetos.
A first investigation of γp→ KsΣ+→ pπ°π° pπ°
Data on the reaction γp → p 3π° shows indications for events due to the reaction γp→ KsΣ+. In this theses, this data will be explored further to investigate whether beam asymmetries for this interesting final state can be extracted from the data.
P̅ANDA
Investigation of possible damages of PCB-prototypes after irradiation
For the final readout of the crystals in the forward-endcap of the PANDA central calorimeter, the crystal signals, the low voltage as well as further control signals of the 4x4 or 2x4 crystal detector submodules will be transferred via a patch panel. The high voltage (HV) on the other hand will be regulated on an additional HV-regulation board before transferred to the photosensors attached to the crystals (Avalanche Photo Diodes, APDs). Since the APD detector modules of the forward-endcap of the calorimeter are still placed in an area where radiation and therefore radiation damage plays a role extensive tests of the prototype of the HV-regulation board are necessary and will be performed within this thesis.
Recalibration of the ADC and potentiometer on the HV regulation board after possible radiation damage - method development and tests
For the final readout of the crystals in the forward-endcap of the PANDA central calorimeter, the crystal signals, the low voltage as well as further control signals of the 4x4 or 2x4 crystal detector submodules will be transferred via a patch panel. The HV on the other hand will be regulated on an additional HV-regulation board before transferred to the photosensors attached to the crystals (APDs). Since the APD-modules detector modules of the forward-endcap of the calorimeter are still placed in an area where radiation and therefore radiation damage plays a role, a method to recalibrate the on board ADC and potentiometer needs to be developed. The development of a recalibration method as well as the respective tests will be the aim of this thesis.
Study of the physics performance of the PANDA detector for specific reactions
The PANDA detector at FAIR is presently build within a large international collaboration. Of course not only setting up the detector itself but also the preparation of the reconstruction and analysis tools is of large importance. This is done based on simulated data. Within several possible theses, the simulation of reactions like pp→ ηπ° or pp→ ηπ°π° (Important for the low mass glueball search) or pp→ Ξ+Ξ-π° (double strange baryon spectroscopy) are planned. These theses will include in addition to the data analysis part also a software development part, which aims at an improvement of the existing simulation and reconstruction software based on the reaction channels investigated. Software/programming experience needed.
Optimisation of the simulation and reconstruction of photons in the PANDA calorimeter
The observation of photons with good energy and angular resolution is one of the important tasks to reach with the electromagnetic calorimeter of the PANDA detector. This theses aims at an optimisation of the simulation and reconstruction of photons in the electromagnetic calorimeter starting with the forward endcap. Software/programming experience needed.
Optimization of the simulation and reconstruction of photons in the PANDA calorimeter
Within this theses, the effect of other detector components and in general of material in front of the EMC will be studied and optimized reconstruction procedures will be developed.
Simulation and reconstruction of cosmics in the PANDA-EMC forward-endcap
As soon as the forward-endcap of the electromagnetic calorimeter is build up, it will be tested with cosmics. Afterwards in-beam tests are planned. To be well prepared for the first tests with Cosmics, this thesis aims at a detailed simulation. It is planned to use the Cosmic-ray Shower Library of the Lawrence Livermore National Laboratory to generate cosmics considering properly their angular and energy distributions. Tracking the particles with Geant through the detector system, a realistic simulation of cosmics in the EMC-forward-endcap of complicated geometry can be performed. After reconstruction, the expected energy deposits in the different crystals depending on specific event topologies can be determined. Topologies will be identified based on the simulation which will allow the most sensitive test cases in the later test measurements.
Examples for Bachelor-thesis subjects
Crystal Barrel/TAPS Experiment
Newly implemented SADC-readout of the Crystal Barrel Calorimeter - Cross check of first data taken
The Crystal Barrel calorimeter has been upgraded. The new readout of the CsI(Tl) crystals is now done by avalanche photo diodes (APDs). This readout is fast enough to not only provide an energy but also a time and a trigger signal. In the next step of upgrading the detector system, Sampling-ADCs (SADCs) will replace the presently used integrating ADCs (QDCs). The SADC-development is finalized and the SADCs will be implemented and tested within the next months. During a test-phase they will be used in parallel to the presently used QDCs. Within this thesis the first data taken with a calorimeter fully equipped by an SADC-readout will be analyzed and compared to the QDC-data to identify possible problems if they should be occurring.
Monitoring of the discriminator thresholds
Discriminator thresholds determine if the information of a detector component is e.g. further processed. The discriminator thresholds in the Crystal Barrel calorimeter determine e.g. whether certain signals in the crystals are high enough to contribute to the trigger signal, which finally decides whether or not e.g. the event is written to disk. In addition, only for events above the discriminator threshold a time for the respective crystal is stored. Similarly signals above a discriminator threshold indicate that a certain plastic scintillator in the tagging system was hit by an electron. Obviously the knowledge of the discriminator thresholds set in the experiment is important. The aim of this thesis is therefore to include this information into the slowcontrol database (SQL) for later use and in addition to monitor the thresholds as part of the online monitoring during the beamtime.
Optimisation of the energy correction function of the TAPS-detector
Based on Monte Carlo simulations an energy correction function (ECF) has been developed for the Crystal Barrel as well as for the TAPS calorimeter. This energy correction function takes into account the energy losses of a photon with a certain energy at a certain angle in the detector system. It is e.g. obvious that in certain areas, e.g. at the edge of the detector system, a larger part of the electromagnetic shower of a photon might be lost compared to areas more central in the detector system. In addition, holding structures are responsible for energy losses. The existing ECF for TAPS has proven in analyses to have some shortcomings, which should be removed within the scope of this theses. The theses would therefore study the interaction of photons with the TAPS detector system and based on the results optimise the existing ECF.
Control of the VME-crates of the experiment (voltages, temperatures)
VME crates are hosting e.g. Time Digital Converter (TDC) or trigger modules of the experiment. The aim of this thesis is to control e.g. the voltages supplied by the crates as well as their temperatures. To do so this information needs to be read out, saved as part of the slowcontrol system and should in addition be visualized on the slowcontrol website of the experiment.
P̅ANDA
Tests of the High voltage (HV) regulation board
For the final readout of the crystals in the Forward Endcap of the PANDA central calorimeter, the crystal signals, the low voltage as well as further control signals of the 4x4 or 2x4 crystal detector submodules will be transferred via a patch panel. The HV on the other hand will be regulated on an additional HV-regulation board before transferred to the photosensors attached to the crystals (APDs). The HV regulation is controlled via I²C. Within this thesis it will be tested whether there is any influence of the I²C-signals on the APD-signals themselves. In addition, a long term test on the stability of the HV provided will be performed.