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Antineutron
The antineutron is the antiparticle of the neutron with symbol . It differs from the neutron only in that some of its properties have equal magnitude but opposite sign. It has the same mass as the neutron, and no net electric charge, but has opposite baryon number (+1 for neutron, −1 for the antineutron). This is because the antineutron is composed of antiquarks, while neutrons are composed of quarks. The antineutron consists of one up antiquark and two down antiquarks. Background The antineutron was discovered in proton–antiproton collisions at the Bevatron (Lawrence Berkeley National Laboratory) by the team of Bruce Cork, Glen Lambertson, Oreste Piccioni, and William Wenzel in 1956, one year after the antiproton was discovered. Since the antineutron is electrically neutral, it cannot easily be observed directly. Instead, the products of its annihilation with ordinary matter are observed. In theory, a free antineutron should decay into an antiproton, a positron, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron
The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nuclear fission in 1938, the first self-sustaining nuclear reactor (Chicago Pile-1, 1942) and the first nuclear weapon (Trinity (nuclear test), Trinity, 1945). Neutrons are found, together with a similar number of protons in the atomic nucleus, nuclei of atoms. Atoms of a chemical element that differ only in neutron number are called isotopes. Free neutrons are produced copiously in nuclear fission and nuclear fusion, fusion. They are a primary contributor to the nucleosynthesis of chemical elements within stars through fission, fusion, and neutron capture processes. Neutron stars, formed from massive collapsing stars, consist of neutrons at the density of atomic nuclei but a total mass more than the Sun. Neutron properties and interactions ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antiparticle
In particle physics, every type of particle of "ordinary" matter (as opposed to antimatter) is associated with an antiparticle with the same mass but with opposite physical charges (such as electric charge). For example, the antiparticle of the electron is the positron (also known as an antielectron). While the electron has a negative electric charge, the positron has a positive electric charge, and is produced naturally in certain types of radioactive decay. The opposite is also true: the antiparticle of the positron is the electron. Some particles, such as the photon, are their own antiparticle. Otherwise, for each pair of antiparticle partners, one is designated as the normal particle (the one that occurs in matter usually interacted with in daily life). The other (usually given the prefix "anti-") is designated the ''antiparticle''. Particle–antiparticle pairs can annihilate each other, producing photons; since the charges of the particle and antiparticle are opposite, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oreste Piccioni
Oreste Piccioni (October 24, 1915 – April 13, 2002) was an Italian-American physicist who made important contributions to elementary particle physics. He is the co-discoverer of the antineutron. Biography He was a graduate student of Enrico Fermi at the University of Rome, receiving his doctorate in 1938."Oreste Piccioni, Leading Physicist, Dies at 86", Obituary, by Kenneth Chang, ''New York Times'' , April 27, 2002/ref>Wenzle, W.A., Swanson, R.A., and Mehlhop, W.A.W., Physics Today, April 2003/ref> Remaining in Italy during World War II, he did fundamental research under difficult conditions in the basement of a high school, which first clarified the nature of the muon.M. Conversi, E. Pancini, and O. Piccioni, Phys. Rev. 68 (1945) 232 In 1946 he emigrated to the United States, where he worked first at the Massachusetts Institute of Technology with Bruno Rossi, and then at Brookhaven National Laboratory's Cosmotron, developing faster nuclear electronics and ess ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baryon Number
In particle physics, the baryon number (B) is an additive quantum number of a system. It is defined as B = \frac(n_\text - n_), where is the number of quarks, and is the number of antiquarks. Baryons (three quarks) have B = +1, mesons (one quark, one antiquark) have B = 0, and antibaryons (three antiquarks) have B = −1. Exotic hadrons like pentaquarks (four quarks, one antiquark) and tetraquarks (two quarks, two antiquarks) are also classified as baryons and mesons depending on their baryon number. In the standard model B conservation is an accidental symmetry which means that it appears in the standard model but is often violated when going beyond it. Physics beyond the Standard Model theories that contain baryon number violation are, for example, Standard Model with extra dimensions, Supersymmetry, Grand Unified Theory and String theory. Baryon number vs. quark number Quarks carry not only electric charge, but also charges such as color charge and weak iso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bruce Cork
Bruce Cork (1916 – October 7, 1994) was a physicist who discovered the antineutron in 1956 while working at the Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory (LBNL, Berkeley Lab) is a Federally funded research and development centers, federally funded research and development center in the Berkeley Hills, hills of Berkeley, California, United States. Established i .... He retired from Lawrence in 1986. He died October 7, 1994, at the age of 78 after a long illness. External links Includes Obituary 1916 births 1994 deaths 20th-century American physicists American nuclear physicists {{US-physicist-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annihilation
In particle physics, annihilation is the process that occurs when a subatomic particle collides with its respective antiparticle to produce other particles, such as an electron colliding with a positron to produce two photons. The total energy and momentum of the initial pair are conserved in the process and distributed among a set of other particles in the final state. Antiparticles have exactly opposite additive quantum numbers from particles, so the sums of all quantum numbers of such an original pair are zero. Hence, any set of particles may be produced whose total quantum numbers are also zero as long as conservation of energy, conservation of momentum, and conservation of spin are obeyed. During a low-energy annihilation, photon production is favored, since these particles have no mass. High-energy particle colliders produce annihilations where a wide variety of exotic heavy particles are created. The word "annihilation" takes its use informally for the interaction of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bevatron
The Bevatron was a particle accelerator — specifically, a Weak focusing, weak-focusing proton synchrotron — located at Lawrence Berkeley National Laboratory, U.S., which began operations in 1954. The antiproton was discovered there in 1955, resulting in the 1959 Nobel Prize in physics for Emilio Segrè and Owen Chamberlain. It accelerated protons into a fixed target, and was named for its ability to impart energies of billions of Electronvolt, eV ("billions of eV synchrotron"). Antiprotons When the Bevatron was designed, scientists strongly suspected—but had not yet confirmed—that every particle had a corresponding antiparticle with an opposite charge but otherwise identical properties, a concept known as C-symmetry, charge symmetry. The anti-electron, or positron, had been first observed in the early 1930s and theoretically understood as a consequence of the Dirac equation at about the same time. Following World War II, positive and negative muons and pions wer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutrino
A neutrino ( ; denoted by the Greek letter ) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small ('' -ino'') that it was long thought to be zero. The rest mass of the neutrino is much smaller than that of the other known elementary particles (excluding massless particles). The weak force has a very short range, the gravitational interaction is extremely weak due to the very small mass of the neutrino, and neutrinos do not participate in the electromagnetic interaction or the strong interaction. Consequently, neutrinos typically pass through normal matter unimpeded and with no detectable effect. Weak interactions create neutrinos in one of three leptonic flavors: # electron neutrino, # muon neutrino, # tau neutrino, Each flavor is associated with the correspondingly named charged lepton. Although neutrinos were long believed to be mas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Down Antiquark
The down quark (symbol: d) is a type of elementary particle, and a major constituent of matter. The down quark is the second-lightest of all quarks, and combines with other quarks to form composite particles called hadrons. Down quarks are most commonly found in atomic nuclei, where it combines with up quarks to form protons and neutrons. The proton is made of one down quark with two up quarks, and the neutron is made up of two down quarks with one up quark. Because they are found in every single known atom, down quarks are present in all everyday matter that we interact with. The down quark is part of the first generation of matter, has an electric charge of − ''e'' and a bare mass of . Like all quarks, the down quark is an elementary fermion with spin , and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the down quark is the down antiquark (sometimes called ''antidown quark' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory (LBNL, Berkeley Lab) is a Federally funded research and development centers, federally funded research and development center in the Berkeley Hills, hills of Berkeley, California, United States. Established in 1931 by the University of California (UC), the laboratory is sponsored by the United States Department of Energy and administered by the UC system. Ernest Lawrence, who won the Nobel prize for inventing the cyclotron, founded the lab and served as its director until his death in 1958. Located in the Berkeley Hills, the lab overlooks the campus of the University of California, Berkeley. Scientific research The mission of Berkeley Lab is to bring science solutions to the world. The research at Berkeley Lab has four main themes: discovery science, energy, earth systems, and the future of science. The Laboratory's 22 scientific divisions are organized within six areas of research: Computing Sciences, Physical Sciences, Earth and Environmenta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
