PDF - THEP Mainz

Abstract
The standard model of elementary particle physics (SM) is perhaps the most significant
theory in physics. It describes the interacting matter and gauge fields at high prescision.
Nevertheless, there are a few requirements, which are not fulfilled by the SM, for example
the incorporation of gravity, neutrino oscillations and further open questions.
On the way to a more comprehensive theory, one can make use of an effective power series
ansatz, which describes the SM physics as well as new phenomena. We exploit this ansatz
to parameterize new effects with the help of a new mass scale and a set of new coupling
constants. In the lowest order, one retrieves the SM. Higher order effects describe the
new physics. Requiring certain properties under symmetry transformations gives a proper
number of effective operators with mass dimension six. These operators are the starting
point of our considerations.
First, we calculate decay rates and cross sections, respectively, for selected processes under
the assumption that only one new operator contributes at a time. Assuming that the
observable’s additional contribution is smaller than the experimental error, we give upper
limits to the new coupling constant depending on the new mass scale. For this purpose we
use leptonic and certain semileptonic precision data.
On the one hand, the results presented in this thesis give physicists the opportunity to
decide, which experiments are good candidates to increase precision. On the other hand,
they show which experiment has the most promising potential for discoveries.