"Subatomic particle In the physical sciences, subatomic particles are particles much smaller than atoms. The two types of subatomic particles are: elementary particles, which according to current theories are not made of other particles; and ""composite"" particles. Particle physics and nuclear physics study these particles and how they interact. The idea of a particle underwent serious rethinking when experiments showed that light could behave like a stream of particles (called photons) as well as exhibiting wave-like properties. This led to the new concept of wave–particle duality to reflect that quantum-scale ""particles"" behave like both particles and waves (they are sometimes"
"without having an electric charge. For example, the neutron is electrically neutral but has a non-zero magnetic moment because of its internal quark structure. We can calculate the observable spin magnetic moment, a vector, """", for a sub-atomic particle with charge ""q"", mass ""m"", and spin angular momentum (also a vector), , via: where formula_1 is the gyromagnetic ratio, ""g"" is a dimensionless number, called the g-factor, ""q"" is the charge, and ""m"" is the mass. The ""g""-factor depends on the particle: it is ""g"" = −2.0023 for the electron, ""g"" = 5.586 for the proton, and for the neutron."
"Electron The electron is a subatomic particle, symbol or , whose electric charge is negative one elementary charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the electron include an intrinsic angular momentum (spin) of a half-integer value, expressed in units of the reduced Planck constant, ""ħ"". As it is a fermion, no two electrons can occupy the same quantum state, in accordance with"
"Neutrino A neutrino ( or ) (denoted by the Greek letter ν) is a fermion (an elementary particle with half-integer spin) that interacts only via the weak subatomic force and gravity. The mass of the neutrino is much smaller than that of the other known elementary particles. Although only differences of squares of the three mass values are known as of 2016, cosmological observations imply that the sum of the three masses must be less than one millionth that of the electron. The neutrino is so named because it is electrically neutral and because its rest mass is so small"
"massive spin-zero particle, was proposed as the Higgs boson. (see 1964 PRL symmetry breaking papers) and is a key building block in the Standard Model. It has no intrinsic spin, and for that reason is classified as a boson (like the gauge bosons, which have integer spin). The Higgs boson plays a unique role in the Standard Model, by explaining why the other elementary particles, except the photon and gluon, are massive. In particular, the Higgs boson explains why the photon has no mass, while the W and Z bosons are very heavy. Elementary-particle masses, and the differences between electromagnetism"
"smaller particles, in modern scientific usage the atom is composed of various subatomic particles. The constituent particles of an atom are the electron, the proton and the neutron; all three are fermions. However, the hydrogen-1 atom has no neutrons and the hydron ion has no electrons. The electron is by far the least massive of these particles at , with a negative electrical charge and a size that is too small to be measured using available techniques. It was the lightest particle with a positive rest mass measured, until the discovery of neutrino mass. Under ordinary conditions, electrons are bound"
"frequently in atomic physics and nuclear physics, where one often needs to determine the total spin of a collection of particles. Since the only observed fundamental particle with zero spin is the extremely inaccessible Higgs boson, singlets in everyday physics are necessarily composed of sets of particles whose individual spins are non-zero, e.g. 1/2 or 1. The origin of the term ""singlet"" is that bound quantum systems with zero net angular momentum emit photons within a single spectral line, as opposed to double lines (doublet state) or triple lines (triplet state). The number of spectral lines formula_2 in this singlet-style"
"any atomic nucleus, have the intrinsic quantum property of spin, an intrinsic angular momentum analogous to the classical angular momentum of a spinning sphere. The overall spin of the nucleus is determined by the spin quantum number ""S"". If the numbers of both the protons and neutrons in a given nuclide are even then , i.e. there is no overall spin. Then, just as electrons pair up in nondegenerate atomic orbitals, so do even numbers of protons or even numbers of neutrons (both of which are also spin formula_1 particles and hence fermions), giving zero overall spin. However, a proton"
"Electron neutrino The electron neutrino () is a subatomic lepton elementary particle which has no net electric charge. Together with the electron it forms the first generation of leptons, hence the name electron neutrino. It was first hypothesized by Wolfgang Pauli in 1930, to account for missing momentum and missing energy in beta decay, and was discovered in 1956 by a team led by Clyde Cowan and Frederick Reines (see Cowan–Reines neutrino experiment). In the early 1900s, theories predicted that the electrons resulting from beta decay should have been emitted at a specific energy. However, in 1914, James Chadwick showed"
"0, respectively. Thus, the neutron has a charge of 0 (zero), and therefore is electrically neutral; indeed, the term ""neutron"" comes from the fact that a neutron is electrically neutral. The mass of the proton and neutron is quite similar: The proton is or , while the neutron is or . The neutron is roughly 0.13% heavier. The similarity in mass can be explained roughly by the slight difference in masses of up quarks and down quarks composing the nucleons. However, a detailed explanation remains an unsolved problem in particle physics. The spin of both protons and neutrons is ,"
"Tau neutrino The tau neutrino or tauon neutrino is a subatomic elementary particle which has the symbol and no net electric charge. Together with the tau, it forms the third generation of leptons, hence the name tau neutrino. Its existence was immediately implied after the tau particle was detected in a series of experiments between 1974 and 1977 by Martin Lewis Perl with his colleagues at the SLAC–LBL group. The discovery of the tau neutrino was announced in July 2000 by the DONUT collaboration (Direct Observation of the Nu Tau). The tau neutrino is last of the leptons, and is"
"Massless particle In particle physics, a massless particle is an elementary particle whose invariant mass is zero. The two known massless particles are both gauge bosons: the photon (carrier of electromagnetism) and the gluon (carrier of the strong force). However, gluons are never observed as free particles, since they are confined within hadrons. Neutrinos were originally thought to be massless. However, because neutrinos change flavor as they travel, at least two of the types of neutrinos must have mass. The discovery of this phenomenon, known as neutrino oscillation, led to Canadian scientist Arthur B. McDonald and Japanese scientist Takaaki Kajita"
"spin magnetic moment of a Dirac particle, a charged, spin 1/2 elementary particle, with a proton's mass ""m"". In SI units, the nuclear magneton is where ""e"" is the elementary charge and ""ħ"" is the reduced Planck constant. The magnetic moment of this particle is parallel to its spin. Since the neutron has no charge, it should have no magnetic moment by this expression. The non-zero magnetic moment of the neutron indicates that it is not an elementary particle. The sign of the neutron's magnetic moment is that of a negatively charged particle. Similarly, the fact that the magnetic moment"
"their spin directions (""up"" and ""down"") oppose each other; that is, they are antiparallel. The simplest possible bound particle pair capable of exhibiting the singlet state is positronium, which consists of an electron and positron (antielectron) bound by their opposite electric charges. The electron and positron in positronium can also have identical or parallel spin orientations, which results in an experimentally distinct form of positronium with a spin 1 or triplet state. An unbound singlet consists of a pair of entities small enough to exhibit quantum behavior (e.g. particles, atoms, or small molecules), not necessarily of the same type, for"
"Tau (particle) The tau (τ), also called the tau lepton, tau particle, or tauon, is an elementary particle similar to the electron, with negative electric charge and a spin of. Together with the electron, the muon, and the three neutrinos, it is a lepton. Like all elementary particles with half-integer spin, the tau has a corresponding antiparticle of opposite charge but equal mass and spin, which in the tau's case is the antitau (also called the ""positive tau""). Tau particles are denoted by and the antitau by . Tau leptons have a lifetime of and a mass of (compared to"
"Muon The muon (; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 ""e"" and a spin of 1/2, but with a much greater mass. It is classified as a lepton. As is the case with other leptons, the muon is not believed to have any sub-structure—that is, it is not thought to be composed of any simpler particles. The muon is an unstable subatomic particle with a mean lifetime of , much longer than many other subatomic particles. As with the decay of the"
"of a massless particle is Spin(""d"" − 1) × Spin(""d"" − ""k"" − 1), where ""k"" is equal to the number ""d"" of spatial dimensions minus the number ""d"" − ""k"" of time dimensions. (See helicity (particle physics)) For example, in our world, this is 3 − 1 = 2. Due to the mod 8 Bott periodicity of the homotopy groups of the Lorentz group, really we only need to consider ""k"" modulo 8. For any value of ""k"" there is a Dirac representation, which is always of real dimension formula_4 where formula_5 is the greatest integer less than or"
"the electron in a ground state hydrogen atom has no angular momentum at all—illustrating how the ""planetary orbit"" differs from electron motion. There exist two different spin isomers of hydrogen diatomic molecules that differ by the relative spin of their nuclei. In the orthohydrogen form, the spins of the two protons are parallel and form a triplet state with a molecular spin quantum number of 1 (+); in the parahydrogen form the spins are antiparallel and form a singlet with a molecular spin quantum number of 0 (–). At standard temperature and pressure, hydrogen gas contains about 25% of the"
"He, Na or P, have a non–zero spin and therefore a magnetic moment. In the case of the so-called spin- nuclei, such as H, there are two spin states, sometimes referred to as ""up"" and ""down"". Nuclei such as C have no unpaired neutrons or protons, and no net spin; however, the isotope C does. When these spins are placed in a strong external magnetic field they precess around an axis along the direction of the field. Protons align in two energy eigenstates (the Zeeman effect): one low-energy and one high-energy, which are separated by a very small splitting energy."
"a mass of 939,565,413.3 eV/c, or , or . The neutron has a mean square radius of about , or 0.8 fm, and it is a spin-½ fermion. The neutron has no measurable electric charge. With its positive electric charge, the proton is directly influenced by electric fields, whereas the neutron is unaffected by electric fields. The neutron has a magnetic moment, however, so the neutron is influenced by magnetic fields. The neutron's magnetic moment has a negative value, because its orientation is opposite to the neutron's spin. A free neutron is unstable, decaying to a proton, electron and antineutrino"
"along with the hypothetical neutralinos, sterile neutrinos, and gravitons. For a spin- particle such as the neutralino, being a truly neutral particle implies being a Majorana fermion. Composite particles can also be truly neutral. The best known example is onium, a system composed of a particle forming a bound state with its own antiparticle. Truly neutral particle In particle physics, a truly neutral particle is a subatomic particle with all its charges equal to zero. This not only requires particles to be electrically neutral, but also requires that all of their other charges (like the colour charge) are neutral. Such"
"Muon neutrino The muon neutrino is a lepton, an elementary subatomic particle which has the symbol and no net electric charge. Together with the muon it forms the second generation of leptons, hence the name muon neutrino. It was first hypothesized in the early 1940s by several people, and was discovered in 1962 by Leon Lederman, Melvin Schwartz and Jack Steinberger. The discovery was rewarded with the 1988 Nobel Prize in Physics. In 1962 Leon M. Lederman, Melvin Schwartz and Jack Steinberger established by performing an experiment at the Brookhaven National Laboratory that more than one type of neutrino exists"
"all spinless particles with positive, negative as well as zero charge. Any solution of the free Dirac equation is, component-wise, a solution of the free Klein–Gordon equation. The equation does not form the basis of a consistent quantum relativistic ""one-particle"" theory. There is no known such theory for particles of any spin. For full reconciliation of quantum mechanics with special relativity quantum field theory is needed, in which the Klein–Gordon equation reemerges as the equation obeyed by the components of all free quantum fields. In quantum field theory, the solutions of the free (noninteracting) versions of the original equations still"
"left the nucleus with a net spin of . Rasetti discovered, however, that nitrogen-14 had a spin of 1. In 1932 Chadwick realized that radiation that had been observed by Walther Bothe, Herbert Becker, Irène and Frédéric Joliot-Curie was actually due to a neutral particle of about the same mass as the proton, that he called the neutron (following a suggestion from Rutherford about the need for such a particle). In the same year Dmitri Ivanenko suggested that there were no electrons in the nucleus — only protons and neutrons — and that neutrons were spin particles which explained the"
"of anti-parallel spin neutrons (of total spin zero for the neutron-spin pair), plus a proton of spin . Therefore, the tritium total nuclear spin value is again , just like for the simpler, abundant hydrogen isotope, H nucleus (the ""proton""). The NMR absorption frequency for tritium is also similar to that of H. In many other cases of ""non-radioactive"" nuclei, the overall spin is also non-zero. For example, the nucleus has an overall spin value . A non-zero spin formula_2 is always associated with a non-zero magnetic dipole moment, formula_3, via the relation formula_4 where ""γ"" is the gyromagnetic ratio."
"Another one is an onium atom called ""true tauonium"" and is difficult to detect due to tau's extremely short lifetime at low (non-relativistic) energies needed to form this atom. Its detection is important for quantum electrodynamics. Tau (particle) The tau (τ), also called the tau lepton, tau particle, or tauon, is an elementary particle similar to the electron, with negative electric charge and a spin of. Together with the electron, the muon, and the three neutrinos, it is a lepton. Like all elementary particles with half-integer spin, the tau has a corresponding antiparticle of opposite charge but equal mass and"
"with no orbital angular momentum) baryons can also be pictured thus. Each quark is a spin 1/2 particle. The spins can be pointed up, or down. In ground state, the two light quarks point up-down to give a zero spin diquark. This then combines with the charm quark to give a spin 1/2 particle. In the , the two light quarks combine to give a spin 1 diquark, which then combines with the charm quark to give either a spin 1/2 particle, or a spin 3/2 particle (normally known as a ). It is the rules of quantum mechanics that"
"The implied mass range is from 0–3 eV. In 2016, scientists at the IceCube Neutrino Observatory did not find any evidence for the sterile neutrino. However, in May 2018, physicists of the MiniBooNE experiment reported a stronger neutrino oscillation signal than expected, a possible hint of sterile neutrinos. Sterile neutrino Sterile neutrinos (or inert neutrinos) are hypothetical particles (neutral leptons – neutrinos) that interact only via gravity and do not interact via any of the fundamental interactions of the Standard Model. The term ""sterile neutrino"" is used to distinguish them from the known ""active neutrinos"" in the Standard Model, which"
"do not have any up or down quarks, they all have isospin 0. † Particle (or quantity, i.e. spin) has neither been observed nor indicated. The particle is a ""doubly strange"" baryon containing two strange quarks and a bottom quark. A discovery of this particle was first claimed in September 2008 by physicists working on the DØ experiment at the Tevatron facility of the Fermi National Accelerator Laboratory. However, the reported mass of was significantly higher than expected in the quark model. The apparent discrepancy from the Standard Model has since been dubbed the "" puzzle"". In May 2009, the"
"will have no spin when it has even numbers of both neutrons and protons, but for other cases of odd numbers, the nucleus may have a spin. Normally nuclei with spin are aligned in random directions because of thermal equilibrium. However, for certain elements (such as xenon-129) it is possible to polarize a significant proportion of the nuclear spin states so that they are aligned in the same direction—a condition called hyperpolarization. This has important applications in magnetic resonance imaging. The potential energy of an electron in an atom is negative, its dependence of its position reaches the minimum (the"
"Spin-½ In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. All known elementary fermions have a spin of . Particles having net spin include the proton, neutron, electron, neutrino, and quarks. The dynamics of spin- objects cannot be accurately described using classical physics; they are among the simplest systems which require quantum mechanics to describe them. As such, the study of the behavior of spin- systems forms a central part of quantum mechanics. A spin- particle is characterized by an angular momentum quantum number for spin s"
"to be small, like that of the η. The particles belong to the ""pseudo-scalar"" nonet of mesons which have spin and negative parity, and and have zero total isospin, ""I"", and zero strangeness and hypercharge. Each quark which appears in an particle is accompanied by its antiquark (the particle overall is ""flavourless"") and all the main quantum numbers are zero. The basic SU(3) symmetry theory of quarks for the three lightest quarks, which only takes into account the strong force, predicts corresponding particles and The subscripts refer to the fact that η belongs to a singlet (which is fully antisymmetrical)"
"one electron in each of the p orbitals and the high energy form is the singlet state with an electron pair filling one p orbital and the other one vacant. As with carbenes, a strong correlation exists between the spin density on the nitrogen atom which can be calculated in silico and the zero-field splitting parameter ""D"" which can be derived experimentally from electron spin resonance. Small nitrenes such as NH or CFN have D values around 1.8 cm with spin densities close to a maximum value of 2. At the lower end of the scale are molecules with low"