Lauri Kaldamäe will defend his doctoral thesis titled "Fermion mass and spinn polarisation effects in top quark pair production and the decay of the higgs boson" on 17. May 2017 at 16:15 at W. Ostwaldi 1, room A106.
dr Stefan Groote, Institute of Physics, University of Tartu
dr Markus Diehl, DESY, Germany
dr Kristjan Kannike, NICPB, Estonia.
Everything we see and touch in the world, is built up from atoms. However, different from Democritus’ antique opinion, atoms are not the fundamental building blocks. Nowadays’ elementary building blocks are elementary particles like electrons, quarks and bosons. Therefore, to make a tangible and visible thing, an unfathomable number of such tiny building blocks is necessary. If one studies the tiniest things, then it will be inevitably revealed that their behaviour does not comply with our expectations which are based on everyday experience. In the realm of quantum mechanics it is entirely possible for a particle to be in two places at once or to be simultaneously a thing and a wave. In addition to well-known properties that describe items like mass or length, there are some properties (like spin) that cannot be applied to big things. The essence of the thesis is a more precise description of some specific processes that happen to some specific particles. The correlation of spins of jointly created top quark and it’s antiparticle is studied as well as the effect of a lepton to the decay of Higgs boson. The first order corrections to the spin-spin correlation is calculated and opportunity for measuring spin-spin correlations through an angular analysis of movement of the decay products of quarks is discussed. In the calculation of the decay of Higgs boson the created lepton’s mass is taken into account and lepton mass effect to Higgs boson decay probability is found. The originality of the study stems from the inclusion of masses and spins and the analytic presentation of the results, which allows to analyse dependencies on different parameters in detail and to calculate the behaviour in different kinematical limits. These results help to guide future experiments and enable a more detailed comparison with the Standard Model of elementary particles. The aim of this study is not to solve any specific existing modern problem. The motivation and cause for this study is in pushing the boundary of the horizon of the knowledge of the humanity and thus laying a foundation for future technologies.