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Linné on line arrow Physics and the Cosmos arrow Physics and the Cosmos arrow Quarks and leptons arrow WASA, an Uppsala experiment

WASA, an Uppsala experiment

In the WASA/PROMICE experiment at the CELSIUS ring in Uppsala one is colliding protons with protons in order to study particle production and decays at low energies. One is mainly interested in the production mechanism close to threshold when the energy is just enough. In the future one will also be interested in rare decays of mesons. The hope is that this will give a better understanding of the mechanisms which control the interactions between quarks at low energies.


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  In a typical collision a proton (blue) with about 300 MeV kinetic energy collides with another proton (yellow) which is almost at rest. In the collision a neutral pion (red) is produced together with the two protons. The pion is unstable and therefore it decays to two photons (white). Since the pion is more or less at rest the photons must move in opposite directions in order to conserve the momentum.

The WASA detector mainly consists of two parts, one forward and one central detector. The main purpose of the forward detector (red in the picture) is to detect the two outgoing protons (green in the picture above) and measuring their energies. The purpose of the central detector (yellow and orange) is to detect the other particles that are produced, either directly in the interaction or indirectly from the decay of directly produced particles (white above).

The experiment has its own homepage.