High Energy Physics (HEP) is a sub-discipline of Physics which seeks to understand the nature of space and time, the characteristics of the forces governing the interactions of matter and energy, and the origins of the properties of the elementary particles in high energy systems. HEP is an experimental and theoretical science.
Experimental HEP scientists team in thousand-strong collaborations to build the largest instruments ever, aiming to reproduce on Earth, through high-energy hadron collisions in vacuum, the energy densities of the universe at its birth (i.e. Large Hadron Collider, LHC).
At the same time, theoretical particle physicists are linked in global networks through which they collaborate to formulate hypotheses and theories aimed to predict and interpret experimental findings. (Aymar 2009, p.3)
HEP experimental research takes place mainly in international accelerator research centres in Europe, such as the European Organization for Nuclear Research (CERN) in Geneva or the Deutsches Elektronen-Synchrotron (DESY) in Hamburg; in the United States mainly at the Stanford Linear Accelerator Center (SLAC) in California and the Fermi National Accelerator Laboratory (Fermilab) in Illinois; and in Japan at the High Energy Accelerator Research Organization (KEK) in Tsukuba.
HEP theoretical research takes place in hundreds of universities and institutes worldwide, which also host experimental teams building parts of the large detectors used at the large accelerator laboratories and analyzing the data these collect. (Aymar 2008, p.3)