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Humboldt-Universität zu Berlin - Faculty of Mathematics and Natural Sciences - Experimental Particle Physics

Forces

All phenomena observed in nature can be explained by the the four fundamental forces, the strong and weak interaction, electromagnetism and gravity.  Whereas gravity is the the most familiar force to us, known for a long time and well-described, it is gravity about which we have the least understanding.  In the energy range of experimental particle physics its strength is many orders of magnitude smaller compared to the other forces and is therefore negligible.

In our every day life electromagnetism is all around us.  Its description by Maxwell's equations, formulated in the 18th century, was the first example of the unification of two phenomenological different effects within one field theory.  In the view of particle physics, the electromagnetic force is mediated by the photon.  Aside from all electric and optic effects in our life, this force is also responsible for the binding of atoms and molecules.

As we know from radioactive nuclei, particles can decay.  The most prominent example is the beta-decay of a neutron.  According to the description of forces in particle physics, this can be described by the exchange of an interaction particle, the charged W-boson.  Together with the neutral Z-boson they are the exchange particles for the weak interaction.  In measurements it was shown that the electromagnetic and weak forces can also be described by one common theory.  The electroweak interaction is one of the main subjects of recent research in particle physics.

Finally, the strong interaction is responsible for the binding between protons and neutrons in the nuclei.  As we know today, this can be derived from a more fundamental force between the basic components of the proton and the neutron, the quarks.  The exchange particle in this case is called the gluon. The strong interaction is, as the name says, the most powerful one.


Forces | Strong Force | Weak Force | Symmetry | Symmetry Breaking