GSI-SIS-FOPI (Darmstadt, GSI)

GSI-SIS-FOPI (Darmstadt, GSI)
FOPI A DETECTOR FOR THE PHYSICS OF NUCLEAR REACTIONS

URL: http://www-aix.gsi.de/~fopiwww

Nuclear matter, of which atomic nuclei are composed, is a system of strongly interacting particles called nucleons. In its ground state, it behaves in a manner analogous to a fluid, and strongly resists attempts at compression. To double the density of nuclear matter, for example, requires 2x1033 Pascals, a pressure equivalent to twenty times the mass of the earth resting on an area one square millimeter in size. However, a compressed state is required before some of the fundamental properties of nuclear matter reveal themselves. New studies have shown that it is possible, and perhaps even likely, that the properties of the constituents vary according to the density of their surrounding environment. Referring to this phenomenon, scientists talk of a so-called in-medium effect. The properties of these constituents-elementary particles-are well-known when the particles are surrounded by vacuum. However, their masses may vary due to a particular symmetry of the fundamental interaction-the chiral symmetry of Quantum Chromodynamics. In general, such a supposition is true for all hadrons, i.e. particles subject to the strong interaction. Detecting and understanding the processes at work here should help physicists tackle one of the central problems of modern physics-the inability of theoretical physics to provide an explanation of the principle determining the masses of the elementary particles.

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