Experimental Flavor Physics
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Bachelor Thesis Topics

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Sensitivity studies for the measurement of CP violation in D0 -> KS0 KS0 decays (topic not available any more)

So far the violation of the CP symmetry was observed for particles with s and b quarks, but not with c quarks. A promising decay mode of a particle with charm quark where a relatively large effect of CP violation is expected is D0 -> KS0 KS0. Based on simulation studies the precision at which the matter-antimatter asymmetry can be measured should be estimated.

Semileptonic B meson decays to excited D mesons (topic not available any more)

The measured rate of B -> D(*) tau nu decays does not agree with the standard model prediction. To confirm this deviation further measurements, in particular at Belle II, are required. An important background in the measurement are semileptonic decays in excited D mesons. The current status of experimental results and theoretical calculations should be summarized and compared with the implementation in the Belle II simulation.

Sensitivity studies for the test of isospin symmetry at Belle (topic not available any more)

For the reaction e+ e- -> Y(4S) -> B anti-B it is often assumed that pairs of charged and neutral B mesons are produced at equal rate as expected in case of isospin symmetry. But isopsin is only an approximate symmetry. With the world's largest Y(4S) dataset of the Belle experiment it will be possible to make an improved measurement of the decay rates to B+ B- and B0 anti-B0 pairs. These branching fractions are an essential input for many other results and the precision that could be reached should be estimated.

Optimization of background identification with machine learning techniques (topic not available any more)

The decay B -> K(*) nu anti-nu is sensitive to contributions from physics beyond the standard model, but only the Belle II experiment will be able to observe this decay. A challenge in the analysis of this decay is the understanding of backgrounds which requires huge samples of simulated events. To efficiently obtain these samples, background events are selected before the computationally expensive detector response is simulated. Different multivariate techniques for an optimization of the selection should be studied.

Study of improvements of time difference resolution at SuperKEKB (topic not available any more)

The so-called B-factories were built to measure time-dependent CP asymmetries in B meson decays. For such measurements it is essential to determine the difference in the decay time of the two B mesons produced in an e+e- collision. The time difference is obtained from a measurement of the distance of the decay vertices of the two B mesons, using some kinematic approximation. The much smaller beam size at the SuperKEKB accelerator may allow to reduce the uncertainty coming from this approximation and thus be an important improvement for measurements of CP violation at the Belle II experiment.

Vertex fitting algorithms survey

A precise knowledge of the origin of particles is important for many particle physics measurements. Several tools have been developed for determining which particles come from which vertex and for getting the best parameters for the vertex positions and the momenta of the decay particles. Most of the vertex fitter tools, which vary in functionality, interface, and execution speed, were developed for specific experiments. These tools should be systematically evaluated and optimized if needed.

Visualization of Belle II events

For the development of algorithms to reconstruct tracks from individual hits in the detector it is very important to have a good understanding of the detector geometry, the interaction of particles with the detector material, and the resulting signals. A visualization of the detector and the particle trajectories is a powerful tool for developers. The Virtual Reality and Visualisation Centre (V2C) at the LRZ offers a room with projections on 5 sides for a stereocopic display of sientific data (CAVE). The existing Belle II event display should be interfaced to the CAVE and improved to enhance the immersive analysis of events.

Program

A structured program is offered for the bachelor theses.