Schwere Quarkmassen von Jets mit effektiven Feldtheorien

Currently the most precise experimental measurements of the top quark mass are obtained from determinations of the top mass parameter in the Monte-Carlo event generator used for the experimental analyses based on kinematic fits to top quark events. However, the exact relation of the Monte-Carlo top mass parameter to a quantum-field-theoretically well-defined top quark mass is unknown. Thus the interpretation of these measurements is limited, because the results contain an intrinsic ambiguity, which has not even been quantified reliably up to now. The proposed project has the aim to remedy the situation by reaching two goals not achieved in the literature before. The first goal is a high precision theoretical calculation of so-called event shape distributions such as “thrust” for massive quark production at the observable particle level. Event shape distributions have a strong sensitivity to the quark mass and the precise calculation requires the implementation of quark mass definitions consistent at the quantum level. The required computations are carried out using effective field theory methods. These allow for a systematic summation of so-called large logarithmic corrections in perturbation theory as well as a consistent account of so-called hadronization corrections which describe the transition from quarks and gluons to the experimentally observable particles. The second goal is to analyze systematically the relation between the Monte-Carlo top quark mass parameter and field-theoretical top quark mass definitions by comparing the theory calculations of the electron-positron eventshape distributions with the corresponding Monte-Carlo results. This analysis will be carried out using numerical fits and will provide the information how the Monte-Carlo top quark mass parameter can be converted to a well-defined field-theoretic top quark mass definition.