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Coincidence Method
In particle physics, the coincidence method (or coincidence technique) is an experimental design through which particle detectors register two or more simultaneous measurements of a particular event through different interaction channels. Detection can be made by sensing the primary particle and/or through the detection of secondary reaction products. Such a method is used to increase the sensitivity of an experiment to a specific particle interaction, reducing conflation with background interactions by creating more degrees of freedom by which the particle in question may interact. The first notable use of the coincidence method was conducted in 1924 by the Bothe–Geiger coincidence experiment.Bonolis, Luisa. "Walther Bothe and Bruno Rossi: The birth and development of coincidence methods in cosmic-ray physics." Italian Association for the Teaching of Physics, ''arXiv'', 29 Jul. 2011, arxiv.org/pdf/1106.1365.pdf. The higher the rate of interactions or reaction products that can be ...
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Particle Physics
Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the study of combinations of protons and neutrons is called nuclear physics. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and bosons (force-carrying particles). There are three Generation (particle physics), generations of fermions, although ordinary matter is made only from the first fermion generation. The first generation consists of Up quark, up and down quarks which form protons and neutrons, and electrons and electron neutrinos. The three fundamental interactions known to be mediated by bosons are electromagnetism, the weak interaction, and the strong interaction. Quark, Quarks cannot exist on their own but form hadrons. Hadrons that ...
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Compton Scattering
Compton scattering (or the Compton effect) is the quantum theory of high frequency photons scattering following an interaction with a charged particle, usually an electron. Specifically, when the photon hits electrons, it releases loosely bound electrons from the outer valence shells of atoms or molecules. The effect was discovered in 1923 by Arthur Holly Compton while researching the scattering of X-rays by light elements, and earned him the Nobel Prize in Physics in 1927. The Compton effect significantly deviated from dominating classical theories, using both special relativity and quantum mechanics to explain the interaction between high frequency photons and charged particles. Photons can interact with matter at the atomic level (e.g. photoelectric effect and Rayleigh scattering), at the nucleus, or with just an electron. Pair production and the Compton effect occur at the level of the electron. When a high frequency photon scatters due to an interaction with a charged part ...
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Positron
The positron or antielectron is the particle with an electric charge of +1''elementary charge, e'', a Spin (physics), spin of 1/2 (the same as the electron), and the same Electron rest mass, mass as an electron. It is the antiparticle (antimatter counterpart) of the electron. When a positron collides with an electron, annihilation occurs. If this collision occurs at low energies, it results in the production of two or more photons. Positrons can be created by positron emission radioactive decay (through weak interactions), or by pair production from a sufficiently energetic photon which is interacting with an atom in a material. History Theory In 1928, Paul Dirac published a paper proposing that electrons can have both a positive and negative charge. This paper introduced the Dirac equation, a unification of quantum mechanics, special relativity, and the then-new concept of electron Spin (physics), spin to explain the Zeeman effect. The paper did not explicitly predict a ...
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Cadmium Chloride
Cadmium chloride is a white crystalline compound of cadmium and chloride, with the formula CdCl2. This salt is a hygroscopic solid that is highly soluble in water and slightly soluble in alcohol. The crystal structure of cadmium chloride (described below), is a reference for describing other crystal structures. Also known are CdCl2•H2O and the hemipentahydrate CdCl2•2.5H2O. Structure Anhydrous Anhydrous cadmium chloride forms a layered structure consisting of octahedral Cd2+ centers linked with chloride ligands. Cadmium iodide, CdI2, has a similar structure, but the iodide ions are arranged in a HCP lattice, whereas in CdCl2 the chloride ions are arranged in a CCP lattice.N. N. Greenwood, A. Earnshaw, ''Chemistry of the Elements'', 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997. Hydrates The anhydrous form absorbs moisture from the air to form various hydrates. Three of these hydrates have been examined by X-ray crystallography. Chemical properties Cadmium chloride di ...
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Dopant
A dopant (also called a doping agent) is a small amount of a substance added to a material to alter its physical properties, such as electrical or optics, optical properties. The amount of dopant is typically very low compared to the material being doped. When doped into crystalline substances, the dopant's atoms get incorporated into the crystal lattice of the substance. The crystalline materials are frequently either crystals of a semiconductor such as silicon and germanium for use in solid-state electronics, or transparency and translucency, transparent crystals for use in the production of various laser types; however, in some cases of the latter, noncrystalline substances such as glass can also be doped with impurities. In solid-state electronics using the proper types and amounts of dopants in semiconductors is what produces the p-type semiconductors and n-type semiconductors that are essential for making transistors and diodes. Transparent crystals Lasing media The p ...
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Antineutrino
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 massles ...
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Flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phenomena, flux is a vector quantity, describing the magnitude and direction of the flow of a substance or property. In vector calculus flux is a scalar quantity, defined as the surface integral of the perpendicular component of a vector field over a surface. Terminology The word ''flux'' comes from Latin: ''fluxus'' means "flow", and ''fluere'' is "to flow". As '' fluxion'', this term was introduced into differential calculus by Isaac Newton. The concept of heat flux was a key contribution of Joseph Fourier, in the analysis of heat transfer phenomena. His seminal treatise ''Théorie analytique de la chaleur'' (''The Analytical Theory of Heat''), defines ''fluxion'' as a central quantity and proceeds to derive the now well-known expre ...
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Frederick Reines
Frederick Reines ( ; March 16, 1918 – August 26, 1998) was an American physicist. He was awarded the 1995 Nobel Prize in Physics for his co-detection of the neutrino with Clyde Cowan in the neutrino experiment. He may be the only scientist in history "so intimately associated with the discovery of an elementary particle and the subsequent thorough investigation of its fundamental properties." A graduate of Stevens Institute of Technology and New York University, Reines joined the Manhattan Project's Los Alamos Laboratory in 1944, working in the Theoretical Division in Richard Feynman's group. He became a group leader there in 1946. He participated in a number of nuclear tests, culminating in his becoming the director of the Operation Greenhouse test series in the Pacific in 1951. In the early 1950s, working in Hanford Site, Hanford and Savannah River Sites, Reines and Cowan developed the equipment and procedures with which they first detected the supposedly undetectable neutri ...
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Clyde Cowan
Clyde Lorrain Cowan Jr (December 6, 1919 – May 24, 1974) was an American physicist and the co-discoverer of the neutrino along with Frederick Reines. The discovery was made in 1956 in the neutrino experiment. Reines received the Nobel Prize in Physics in 1995. Early life Born the oldest of four children in Detroit, Detroit, Michigan, Cowan's family moved to St. Louis, Missouri, St. Louis, Missouri, where he began his education attending Public school (government funded), public schools. While attending the Missouri University of Science and Technology, Missouri School of Mines and Metallurgy in Rolla, Missouri, Cowan was Editor-in-Chief of the Missouri Miner newspaper from 1939–1940, and graduated in 1940 with a Bachelor of Science, BS in chemical engineering. Military career Cowan was a Captain (United States), captain in the United States Army Air Forces, where he earned a Bronze Star Medal, bronze star in World War II. From 1936–1940 he was in the Reserve Office ...
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Beta Decay
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle (fast energetic electron or positron), transforming into an isobar of that nuclide. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino; or, conversely a proton is converted into a neutron by the emission of a positron with a neutrino in what is called ''positron emission''. Neither the beta particle nor its associated (anti-)neutrino exist within the nucleus prior to beta decay, but are created in the decay process. By this process, unstable atoms obtain a more stable ratio of protons to neutrons. The probability of a nuclide decaying due to beta and other forms of decay is determined by its nuclear binding energy. The binding energies of all existing nuclides form what is called the nuclear band or valley of stability. For either electron or positron emission to be energeticall ...
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Nobel Prize In Physics
The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901, the others being the Nobel Prize in Chemistry, Nobel Prize in Literature, Nobel Peace Prize, and Nobel Prize in Physiology or Medicine. Physics is traditionally the first award presented in the Nobel Prize ceremony. The prize consists of a medal along with a diploma and a certificate for the monetary award. The front side of the medal displays the same profile of Alfred Nobel depicted on the medals for Physics, Chemistry, and Literature. The first Nobel Prize in Physics was awarded to German physicist Wilhelm Röntgen in recognition of the extraordinary services he rendered by the discovery of X-rays. This award is administered by the Nobel Foundation and is widely regarded as the ...
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Coincidence Circuit
In physics and electrical engineering, a coincidence circuit or coincidence gate is an electronic device with one output and two (or more) inputs. The output activates only when the circuit receives signals within a time window accepted as ''at the same time'' and in parallel at both inputs. Coincidence circuits are widely used in particle detectors and in other areas of science and technology. Walther Bothe shared the Nobel Prize for Physics in 1954 "...for his discovery of the method of coincidence and the discoveries subsequently made by it." Bruno Rossi invented the electronic coincidence circuit for implementing the coincidence method. History Bothe and Geiger, 1924-1925 In his Nobel Prize lecture,{{cite web , url=http://nobelprize.org/nobel_prizes/physics/laureates/1954/bothe-lecture.html , title=Nobel Lecture , author=Bothe, Walther , year=1954 , publisher= Nobel Foundation Bothe described how he had implemented the coincidence method in an experiment on Compton s ...
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