Neutrinos - probes for the elementary particles of matter

Neutrinos are massless particles without electric charge. They move in vacuo at the speed of light and penetrate matter easily. Neutrinos produced in high energy particle accelerators are used for the investigation of the internal structure of the atomic nucleus. It is found that the consituents of the nucleus, proton and neutron, themselves consist of 3 point-like objects, called quarks. There is first experimental evidence for a theoretical description of the fundamental force between quarks. Furthermore, neutrino experiments show that the electromagnetic and weak forces in nature are manifestations of one single 'electroweak' force. (orig.)