Popular science description

Particle physics describes the constituents of Nature as a number of elementary particles called quarks and leptons. These quarks and leptons make up all known matter – protons and neutrons, nuclei and atoms – and are the most fundamental building blocks of the Universe known. In particle physics we study how these building blocks interact, and the forces that carry these interactions. These forces are called the electroweak and strong interactions. During the last forty years, a quantum mechanical theory known as the Standard Model was developed, which describes how the quarks and leptons interact by exchanging photons, W- and Z-bosons, and gluons. The Standard Model is an example of a quantum field theory.

The Standard Model is a very successful theory in predicting and explaining experimental observations, the input to the model are some 18 parameters that are fixed experimentally. With these input parameters specified, the Standard Model gives a large set of predictions which can be tested experimentally. Over the past decades a large set of experimental tests universally agree with the predictions of the Standard Model, solidifying it as our best understanding of nature.

Even with the success of the Standard Model there are nevertheless many reasons to expect new physics beyond what we already know. Some of the most prominent include the cosmological observation of dark matter and dark energy, which as to date remains an unknown. Additionally there exist various theoretical problems such as what happens with gravity at high energies. To explain these phenomena it is necessary to go beyond the Standard Model and include additional structure while at the same time not altering the successful experimental predictions.

Beyond the Standard Model theories come in a rich variety and flavour, some of the more popular ones include Supersymmetry which predict that each known particle has a heavy superpartner, some of which could act as a dark matter particle. Other popular possibilities include Grand Unified Theories which states that the known forces unify at a high energy scale, and what we see “down here” is really different aspects of the same force.

In order to judge if a particular beyond the Standard Model theory provides an adequate description of nature it is necessary to connect theory to experiment. This demands considerable calculations to predict signatures that might be seen, for example at the Large Hadron Collider. In our group we specialize on these kind of calculations and use them to study physics both within and beyond the Standard Model using theoretical and computational tools and methods.