Particle physics

Particle physics is a branch of physics that studies the elementary constituents of matter and radiation, and the interactions between them. It is also called high energy physics, because many elementary particles do not occur under normal circumstances in nature, but can be created and detected during energetic collisions of other particles, as is done in particle accelerators.

Subatomic particles

Modern particle physics research is focused on subatomic particles, which have less structure than atoms. These include atomic constituents such as electrons, protons, and neutrons (protons and neutrons are actually composite particles, made up of quarks), particles produced by radiative and scattering processes, such as photons, neutrinos, and muons, as well as a wide range of exotic particles.

Related Topics:
Subatomic particle - Atom - Electron - Proton - Neutron - Quark - Radiative - Scattering - Photon - Neutrino - Muon - Exotic particles

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Strictly speaking, the term particle is something of a misnomer. The objects studied by particle physics obey the principles of quantum mechanics. As such, they exhibit wave-particle duality, displaying particle-like behavior under certain experimental conditions and wave-like behavior in others. Theoretically, they are described neither as waves nor as particles, but as state vectors in an abstract Hilbert space. For a more detailed explanation, see quantum field theory. Following the convention of particle physicists, we will use "elementary particles" to refer to objects such as electrons and photons, with the understanding that these "particles" display wave-like properties as well.

Related Topics:
Quantum mechanics - Wave-particle duality - Wave - State vectors - Hilbert space - Quantum field theory - Electron - Photon

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All the particles observed to date have been catalogued in a quantum field theory called the Standard Model, which is often regarded as particle physics' best achievement to date. The model contains 47 species of elementary particles, some of which can combine to form composite particles, accounting for the hundreds of other species of particles discovered since the 1960s. The Standard Model has been found to agree with almost all the experimental tests conducted to date. However, most particle physicists believe that it is an incomplete description of Nature, and that a more fundamental theory awaits discovery. In recent years, measurements of neutrino mass have provided the first experimental deviations from the Standard Model.

Related Topics:
Quantum field theory - Standard Model - 1960s - Neutrino - Mass

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Particle physics has had a large impact on the philosophy of science. Some in the field still adhere to reductionism, an older concept which has been criticized by various philosophers and scientists. Part of the debate is described below.

Related Topics:
Philosophy of science - Reductionism

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