Research in Elementary Particle and Nuclear Physics
Particle and Nuclear Physics are concerned with the elementary building blocks of matter and the fundamental symmetries and interactions governing the foundations of our world.
We know today that the matter around us is built of point-like objects, quarks and leptons with an experimental upper limit for their size of 10-18m. A total number of six quarks, six anti-quarks as well as six leptons and six anti-leptons have been established experimentally. These fundamental building blocks are arranged in three "families" and we have convincing arguments that this set of families is complete. The behaviour of these elementary particles is governed by four fundamental interactions, namely gravitation, electromagnetic, weak and strong interaction. The interactions between particles are meditated by so-called field bosons, which are the graviton, photon, W- and Z bosons, and the gluon, respectively.
The number of particles and corresponding anti-particles created during the "big-bang" was equal and most particle/anti-particle pairs annihilated. However, a very small imbalance, or spontaneous symmetry breaking, resulted in a small excess of the matter of today's universe.
Modern theoretical and experimental research in particle physics has succeeded to unite the electromagnetic, weak and strong interactions into a unified scheme, called the Standard Model, which is able to describe a large set of experimental data on the properties of elementary particles and simple composites thereof. One of the priorities of this field is the search for the so-called Higgs-Boson, which is thought to be responsible for the masses of the elementary particles.
The Standard Model has many parameters for which values cannot be predicted within the framework of the model and therefore have to be introduced empirically. This shortcoming, together with other theoretical arguments, makes an extension of the Standard Model necessary. Experimental evidence of Physics beyond the Standard Model was only recently provided by the observation of neutrino oscillations, which prove that neutrinos have mass, contrary to the fact that neutrinos are massless within the Standard Model. There are other indications from astro-particle physics that so-called "cold dark matter" exists, requiring the existence of new particles, which are not part of the Standard Model. Due to these facts the search for physics beyond the Standard Model is a major priority of modern experimental and theoretical particle physics.
Future experiments at Fermilab in the U.S. and the LHC at CERN will be able to study the Higgs Boson and establish more physics beyond the standard model.