topic Research

Particle Physics: What holds the core of the universe together

How does mass enter the world?

Particle physics studies the smallest things in our world. It looks for the innermost structures of matter, space and time, as well as for the laws which are the basis for the fundamental forces in the universe. With what we know today, leptons and quarks are the smallest elements in our world. Four fundamental forces exist between them: in addition to the well-known gravity and electro-magnetism, there is the weak force responsible for the radioactive decay of certain atomic cores, and the strong force which keeps quarks in nucleons and nucleons in cores of atoms.

These scientific findings could only be gained because increasingly stronger microscopes in the form of large particle accelerators could be built for particle physics in the last century. Producing the extremely high energy of elementary particles has been essential in enabling an understanding of the smallest dimensions of our world. Such facilities are enormously challenging for engineers and physicists alike, and their construction is always linked to technological innovations.

Despite all the valuable knowledge gained in recent decades, a number of fundamental questions remain unanswered:

• How do elementary particles acquire mass? Or in other words, how does mass enter the world?
• What is the source of the mass of elementary particles?
• Why are there precisely three families of particles and why does the charge of a proton equal exactly that of an electron?
• Is there a universal interaction which is the origin of the four known fundamental forces?
• Are there still unknown forms of matter, for example a new world of super-symmetric particles? Are they the explanation for dark matter in the universe?
• What is the nature of  the dark energy which makes the universe expand more rapidly?
• Are there hidden dimensions in addition to the known three spatial dimensions?

Projects

The Large Hadron Collider (LHC ) at the European Organization for Nuclear Research (CERN) in Geneva has been in operation since 2009. In this circular collider, with a circumference of 27 km, protons are accelerated up to the highest energy ever reached in a laboratory. The LHC is one of the largest facilities for basic research ever built. With its four experiments ALICE, ATLAS, CMS and LHCb, from the very outset, the LHC has been able to verify many previous measurements of the standard model of particle physic with greater precision.

The LHC has an outstanding potential to gain new fundamental insights and make exciting discoveries about the innermost structure of material and its fundamental forces. Thousands of particle physicists from all over the world are carrying out research in the experiments at LHC. To make full use of the LHC's physics potential, it is currently shut down for repairs that will allow it to achieve higher energies. Strategic planning and preparation for the next generation of particle accelerators are already taking place worldwide.

Particle physics also makes use of complementary methods in the search for new evidence. For example, with high precision experiments at lower energies, researchers look for deviations from the standard model (flavor physics, neutrino physics).

CERN Researchers discover new particle

Recording of a procedure at the Large Hadron Collider with possible evidence of the Higgs particle. © CERNOn 13 December 2011, scientists at the European accelerator centre CERN announced the sighting of what could possibly be the first traces of the long-sought Higgs particle. On 4 July 2012, CERN published new research data from the Large Hadron Collider (LHC), the world's largest particle accelerator, which was collected by the ATLAS and CMS experiments between April and mid-June. The researchers had managed a spectacular discovery: a particle with a mass of 125 GeV/c².

GeV stands for "gigaelectronvolts" - or a billion electronvolts - and GeV/c² is a unit of mass used in elementary particle physics. 1 GeV/c² is slightly more that the mass of a hydrogen atom. The probability of error with this discovery is less than one in a million. On 14 March 2013, after the analysis of further data, CERN confirmed that the properties of the discovered particle point strongly towards the Higgs Boson. 

With funding from the Federal Ministry of Education and Research (BMBF), Germany has been significantly involved in the planning, construction and financing of the LHC particle accelerator at CERN. The European Organization for Nuclear Research CERN is the largest particle research laboratory in the world. Today, over 20 European countries participate at CERN. The annual budget in 2012 was approximately 900 million euros.

Germany is the largest investor - about every fifth Euro comes from Germany. Since 2009, German particle physicist Rolf-Dieter Heuer has been general director of CERN. He can be seen discussing the findings announced on 4 July 2012in this video.