The Standard Model summarises all theoretical knowledge about particle physics, that is, which particles that exist and how they interact with each other. There are two types of particles: matter particles and force carriers.

Matter particles consist of six quarks and six leptons that together are divided into three families. For each matter particle there is a corresponding antiparticle with the same properties as the normal particle except that it has the opposite charge. Only the matter particles of the first family exist today. The others were important in the early universe but have since then decayed into particles of the first family.

The quarks have both mass and charge. Different combinations of quarks form hadrons (e.g. protons and neutrons). The leptons (e.g. the electron) are elementary particles, meaning they do not consist of other particles. There are three charged and three neutral leptons. The neutral leptons are very difficult to detect.

Force carriers are particles that mediate an interaction (force). There are three different kinds of force carriers: photons, gluons and vector bosons.

The photon is a massless and neutral elementary particle that mediates the electromagnetism. This is the interaction that acts between electrically charged particles. There are eight gluons that mediate the strong interaction that acts between quarks and keeps hadrons together. The third group of force carriers are the vector bosons (W+, W- och Z0). These mediate the weak interaction that makes particles transform into each other.

The Higgs particle is neither a force carrier nor a matter particle. It appeared in the equations of the Standard Model when these were modified to allow for particles with mass. The scientists hope to demonstrate the existence of the Higgs particle in the new LHC accelerator at CERN.