Group of Hubert Spiesberger

Progress in the understanding of the fundamental interactions of elementary particles requires a close collaboration of experimental and theoretical research. The role of theoretical physics is to provide detailed predictions for scattering and decay processes with elementary particles to a precision that matches the experimental possibilities. Testing the phenomenology of elementary particle properties in high energy scattering processes against theoretical predictions is a first step in the search for new particles and new phenomena.

 

Phenomenology of the Eletroweak and Strong Interactions

The evaluation of theoretical predictions for high-energy particle phenomenology requires, with only a few exceptions, perturbation theory. Important steps in obtaining predictions are analytic calculations, often performed with the help of automatic techniques, and the development of Monte Carlo simulation programs which allow us to obtain a detailed understanding of expected experimental data. 

 

Search for Physics Beyond the Standard Model

Despite of its great success, the Standard Model of the electroweak interactions suffers from a number of deficiencies that motivate the study of extensions. A detailed knowledge of how models beyond the Standard Model signal their presence in scattering processes at high energies is needed if they are not to be overlooked in the bulk of standard physics. Experiments in high energy physics are often complementary in their sensitivity for new physics and combined analyses taking into account a broad spectrum of phenomena are necessary. Theoretical studies can provide prescriptions for experimental tests of new models.

 

Electron Scattering

The present activities of my group is taking up the challenge to derive high-precision predictions for electron proton scattering. The new electron accelerator MESA under construction at the Institute of Nuclear Physics in Mainz will offer the possibility to measure with high precision the parity-violating polarisation asymmetry at low momentum transfer. Such a measurement is expected to lead to a high-precision determination of the weak mixing angle. We will also be able to search for signs of new physics at mass scales in the TeV range, competitive with experiments at highest energies like the LHC.

The planned experiment at MESA will use electrons with low energy scattering off protons at rest where nuclear effects play an important role. Previous experiments with electrons at very high energy (H1 and ZEUS at HERA, Hamburg) have still not completely finished their data analysis, in which I participate. Calculations for future experiments at even higher energies (at the LHeC, CERN) or with heavy nuclear targets (at a speculative electron-ion collider, EIC) are also a subject of my work.

 

Electrical Impedance Tomography

EIT is an imaging technique of medical diagnostics, in which one tries to obtain information on the conductivity distribution in the interior of a body by measuring currents and voltages at the surface of the body. Since different types of tissue have different specific conductivities, EIT would provide a non-invasive complementary modality to more conventional imaging techniques. We have built an electrical impedance tomograph for applications in medical diagnostics such as imaging the interior of a human chest, or mammography.
A challenging part of the project is the development of an image reconstruction algorithm. This requires a good understanding of inverse, ill-posed problems. We are testing different reconstruction algorithms and different geometry layouts of electrodes on a sensing head for mammography. Work group members in Mainz are Prof. Karl Schilcher and Dr.-Ing. Karl-Heinz Georgi. The project is embedded in a collaboration with Prof. Khaled Hayatleh (Brookes University, Oxford) and Prof. Cristiana Sebu (University of Malta).