The fundamental particles:




Fundamental particles are the smallest particles known in physics. In the standard model they are divided in two categories: fermions and bosons. The group of fermions that have a spin of 1/2 consists of leptons and quarks, the basic building blocks of matter. An atom for instance consists of a shell of electrons and a nucleus containing nucleons (protons and neutrons) build of u- and d-quarks.
The bosons have an whole-number spin and transmit the four fundamental interactions. The weak interaction which is responsible e.g. for beta decay, has three bosons : Z, W+ and W-. The boson of the fourth interaction, the gravitation, is supposed to be the graviton which was described theoretically but not found in an experiment yet. The Higgs boson was predicted theoretically as consequence of the higgs field which is responsible for the mass of the particles. The experimental eviedence of this Higgs boson is considered to serve as proove of the Standard model.

Reference: K. Nakamura et al. (Particle Data Group), J. Phys. G 37, 075021 (2010) and 2011 partial update for the 2012 edition.
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