Snippets (text quotes and extracts from authoritative sources)

A Snippet is a short quote or extract (typically a phrase, a sentence, or at most a few sentences) from an authoritative source document such as a specification, technical manual, or design manual. Throughout this site, content is often related to supporting Snippets and each Snippet page links back to the content pages that reference it! The Snippet and Note concepts are very closely related and they support each other.

The Snippet concept is also at the heart of the Parsing Analysis recipe for UML® and SysML®

Kind Snippet quote/extract Source UML keywords SysML keywords Keywords
INFO The neutron has a mean square radius of about 0.8×10−15 m, or 0.8 fm, and it is a spin-½ fermion. Wikipedia neutron
INFO The free neutron has a mass of 939,565,413.3 eV/c2, or 1.674927471×10−27 kg, or 1.00866491588 u. Wikipedia neutron
INFO Beta decay, in which neutrons decay to protons, or vice versa, is governed by the weak force, and it requires the emission or absorption of electrons and neutrinos, or their antiparticles. Wikipedia neutron
INFO Neutrons or protons bound in a nucleus can be stable or unstable, however, depending on the nuclide. Wikipedia neutron
INFO The free proton is stable. Wikipedia neutron
INFO This radioactive decay, known as beta decay, is possible because the mass of the neutron is slightly greater than the proton. Wikipedia neutron
INFO A free neutron is unstable, decaying to a proton, electron and antineutrino with a mean lifetime of just under 15 minutes (881.5±1.5 s). Wikipedia neutron
INFO Since protons and neutrons behave similarly within the nucleus, and each has a mass of approximately one atomic mass unit, they are both referred to as nucleons. Wikipedia neutron
INFO Protons and neutrons constitute the nuclei of atoms. Wikipedia neutron
INFO The neutron is a subatomic particle, symbol n or n0, with no electric charge and a mass slightly greater than that of a proton. Wikipedia neutron
INFO The remainder of a proton's mass is due to quantum chromodynamics binding energy, which includes the kinetic energy of the quarks and the energy of the gluon fields that bind the quarks together. Wikipedia
INFO The rest masses of quarks contribute only about 1% of a proton's mass. Wikipedia
INFO Protons are composite particles composed of three valence quarks: two up quarks of charge + 2/3e and one down quark of charge –1/3e. Wikipedia
INFO Although protons were originally considered fundamental or elementary particles, in the modern Standard Model of particle physics, protons are classified as hadrons, like neutrons, the other nucleon. Wikipedia
INFO The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number (represented by the symbol Z). Since each element has a unique number of protons, each element has its own unique atomic number. Wikipedia
INFO One or more protons are present in the nucleus of every atom; they are a necessary part of the nucleus. Wikipedia
INFO Protons and neutrons, each with masses of approximately one atomic mass unit, are collectively referred to as "nucleons" (particles present in atomic nuclei). Wikipedia
INFO A modern perspective has a proton composed of the valence quarks (up, up, down), the gluons, and transitory pairs of sea quarks. Wikipedia
INFO The two up quarks and one down quark of a proton are held together by the strong force, mediated by gluons. Wikipedia
INFO A proton is a subatomic particle, symbol p or p+, with a positive electric charge of +1e elementary charge and a mass slightly less than that of a neutron. Wikipedia
INFO The quarks that determine the quantum numbers of hadrons are called valence quarks; apart from these, any hadron may contain an indefinite number of virtual "sea" quarks, antiquarks, and gluons, which do not influence its quantum numbers. Wikipedia
INFO Hadrons contain, along with the valence quarks that contribute to their quantum numbers, virtual quark–antiquark pairs known as sea quarks. Wikipedia
INFO Elementary fermions are grouped into three generations, each comprising two leptons and two quarks. Wikipedia
INFO Elementary fermions are grouped into three generations, each comprising two leptons and two quarks. The first generation includes up and down quarks, the second strange and charm quarks, and the third bottom and top quarks. Wikipedia
INFO Antiparticles of quarks are called antiquarks, and are denoted by a bar over the symbol for the corresponding quark, such as ū for an up antiquark. Wikipedia
INFO The Standard Model is the theoretical framework describing all the currently known elementary particles. This model contains six flavors of quarks (q), named up (u), down (d), strange (s), charm (c), bottom (b), and top (t). Wikipedia
INFO For every quark flavor there is a corresponding type of antiparticle, known as an antiquark, that differs from the quark only in that some of its properties (such as the electric charge) have equal magnitude but opposite sign. Wikipedia
INFO Because of this, up and down quarks are generally stable and the most common in the universe, whereas strange, charm, bottom, and top quarks can only be produced in high energy collisions (such as those involving cosmic rays and in particle accelerators). Wikipedia
INFO The heavier quarks rapidly change into up and down quarks through a process of particle decay: the transformation from a higher mass state to a lower mass state. Wikipedia
INFO Up and down quarks have the lowest masses of all quarks. Wikipedia
INFO There are six types, known as flavors, of quarks: up, down, strange, charm, bottom, and top. Wikipedia
INFO A neutrino (denoted by the Greek letter ν) is a fermion (an elementary particle with spin of 1/2) that interacts only via the weak subatomic force and gravity. Wikipedia
INFO Quarks ... are the only known particles whose electric charges are not integer multiples of the elementary charge. Wikipedia
INFO Quarks ... are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as fundamental forces (electromagnetism, gravitation, strong interaction, and weak interaction). Wikipedia
INFO Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin. Wikipedia
INFO Due to a phenomenon known as color confinement, quarks are never found in isolation; they can be found only within hadrons, which include baryons (such as protons and neutrons) and mesons, or in quark–gluon plasmas. Wikipedia
INFO Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Wikipedia
INFO A quark is a type of elementary particle and a fundamental constituent of matter. Wikipedia
INFO The resulting attraction between different quarks causes the formation of composite particles known as hadrons Wikipedia
INFO Unlike leptons, quarks possess color charge, which causes them to engage in the strong interaction. Wikipedia
INFO Both of these decays imply that color is no longer a property of the byproducts. Wikipedia
INFO Uncharged mesons may decay to photons. Wikipedia
INFO Charged mesons decay (sometimes through mediating particles) to form electrons and neutrinos. Wikipedia
INFO All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Wikipedia
INFO In particle physics, mesons are hadronic subatomic particles composed of one quark and one antiquark, bound together by strong interactions. Wikipedia
INFO Four closely related Δ baryons exist: Δ++ (constituent quarks: uuu), Δ+ (uud), Δ0 (udd), and Δ− (ddd), which respectively carry an electric charge of +2 e, +1 e, 0 e, and −1 e. Wikipedia
INFO The Δ baryons have ... a spin of ​3⁄2 ... Wikipedia
INFO In particle physics, a hadron ... is a subatomic composite particle made of two or more quarks ... Wikipedia
INFO Exotic baryons containing five quarks (known as pentaquarks) have also been discovered and studied. Wikipedia
INFO Since baryons are made of three quarks [DISPUTED], their spin vectors can add to make a vector of length S = 3/2, which has four spin projections (Sz = +3/2, Sz = +1/2, Sz = −1/2, and Sz = −3/2), or a vector of length S = 1/2 with two spin projections ... Wikipedia
INFO If two quarks have unaligned spins, the spin vectors add up to make a vector of length S = 0 and has only one spin projection (Sz = 0), etc. Wikipedia
INFO Two quarks can have their spins aligned, in which case the two spin vectors add to make a vector of length S = 1 and three spin projections (Sz = +1, Sz = 0, and Sz = −1). Wikipedia
INFO Because spin projections vary in increments of 1 (that is 1 ħ), a single quark has a spin vector of length 1/2, and has two spin projections (Sz = +1/2 and Sz = −1/2). Wikipedia
INFO Quarks are fermionic particles of spin 1/2 (S = 1/2). Wikipedia
INFO Protons are spin-1/2 fermions and are composed of three valence quarks, making them baryons (a sub-type of hadrons). Wikipedia
INFO The neutron ... is a spin-½ fermion. Wikipedia
INFO The most familiar baryons are protons and neutrons, both of which contain three quarks, and for this reason these particles are sometimes described as triquarks. Wikipedia
INFO They are also classified as fermions, i.e., they have half-integer spin. Wikipedia
INFO Baryons belong to the hadron family of particles, which are the quark-based particles. Wikipedia
INFO In particle physics, a baryon is a type of composite subatomic particle which contains an odd number of valence quarks (at least 3). Wikipedia
INFO According to the spin-statistics theorem in any reasonable relativistic quantum field theory, particles with integer spin are bosons, while particles with half-integer spin are fermions. Wikipedia
INFO Some fermions are elementary particles, such as the electrons, and some are composite particles, such as the protons. Wikipedia
INFO Fermions differ from bosons, which obey Bose–Einstein statistics. Wikipedia
INFO Fermions include all quarks and leptons, as well as all composite particles made of an odd number of these, such as all baryons and many atoms and nuclei. Wikipedia
INFO In particle physics, a fermion is a particle that follows Fermi–Dirac statistics and generally has half odd integer spin 1/2, 3/2 etc. These particles obey the Pauli exclusion principle. Wikipedia
INFO The Pauli exclusion principle is the quantum mechanical principle which states that two or more identical fermions (particles with half-integer spin) cannot occupy the same quantum state within a quantum system simultaneously. Wikipedia
INFO sz is the spin projection quantum number along the z-axis. Wikipedia
INFO there are only two possible values for a spin-1/2 particle: sz = +1/2 and sz = -1/2. These correspond to quantum states in which the spin component is pointing in the +z or −z directions respectively, and are often referred to as "spin up" and "spin down" Wikipedia
INFO Furthermore, it means that a lepton can have only two possible spin states, namely up or down. Wikipedia
INFO Leptons are spin 1/2 particles. The spin-statistics theorem thus implies that they are fermions and thus that they are subject to the Pauli exclusion principle: No two leptons of the same species can be in the same state at the same time. Wikipedia
INFO The positron is symbolized by e+ because it has the same properties as the electron but with a positive rather than negative charge. Wikipedia
INFO As the symbol e is used for the elementary charge, the electron is commonly symbolized by e−, where the minus sign indicates the negative charge. Wikipedia
INFO Within the limits of experimental accuracy, the electron charge is identical to the charge of a proton, but with the opposite sign. Wikipedia
INFO Electrons have an electric charge of −1.602176634×10−19 coulombs, which is used as a standard unit of charge for subatomic particles, and is also called the elementary charge. Wikipedia
INFO The invariant mass of an electron is approximately 9.109×10−31 kilograms, or 5.489×10−4 atomic mass units. On the basis of Einstein's principle of mass–energy equivalence, this mass corresponds to a rest energy of 0.511 MeV. Wikipedia
INFO In theory, a particle and its anti-particle (for example, a proton and an antiproton) have the same mass, but opposite electric charge and other differences in quantum numbers. For example, a proton has positive charge while an antiproton has negative ... Wikipedia
INFO In modern physics, antimatter is defined as matter which is composed of the antiparticles (or "partners") of the corresponding particles of 'ordinary' matter. Wikipedia
INFO 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. Wikipedia
INFO For example, the antiparticle of the electron is the antielectron (which is often referred to as positron). Wikipedia
INFO In particle physics, every type of particle is associated with [an] antiparticle with the same mass but with opposite physical charges (such as electric charge). Wikipedia
INFO According to certain theories, neutrinos may be their own antiparticle. It is not currently known whether this is the case. Wikipedia
INFO For every lepton flavor, there is a corresponding type of antiparticle, known as an antilepton, that differs from the lepton only in that some of its properties have equal magnitude but opposite sign. Wikipedia
INFO electromagnetism ... is proportional to charge, and is thus zero for the electrically neutral neutrinos. Wikipedia
INFO Unlike quarks, however, leptons are not subject to the strong interaction, but they are subject to the other three fundamental interactions: gravitation, the weak interaction, and to electromagnetism ... Wikipedia
INFO Leptons have various intrinsic properties, including electric charge, spin, and mass. Wikipedia
INFO a helium atom in the ground state has spin 0 and behaves like a boson, even though the quarks and electrons which make it up are all fermions. Wikipedia
INFO In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei. Wikipedia
INFO The system is unstable: the two particles annihilate each other to predominantly produce two or three gamma-rays, depending on the relative spin states. Wikipedia
INFO Thus electrons are stable and the most common charged lepton in the universe, whereas muons and taus can only be produced in high energy collisions (such as those involving cosmic rays and those carried out in particle accelerators). Wikipedia
INFO The heavier muons and taus will rapidly change into electrons and neutrinos through a process of particle decay: the transformation from a higher mass state to a lower mass state. Wikipedia
INFO Electrons have the least mass of all the charged leptons. Wikipedia
INFO and the third are the tauonic leptons, comprising the tau ( τ− ) and the tau neutrino ( ν τ) Wikipedia
INFO the second are the muonic leptons, comprising the muon ( μ− ) and the muon neutrino ( ν μ); Wikipedia
INFO The first-generation leptons, also called electronic leptons, comprise the electron ( e− ) and the electron neutrino ( ν e); Wikipedia
INFO There are six types of leptons, known as flavours, grouped in three generations. Wikipedia
INFO The best known of all leptons is the electron. Wikipedia
INFO Positronium (Ps) is a system consisting of an electron and its anti-particle, a positron, bound together into an exotic atom, specifically an onium. Wikipedia
INFO Charged leptons can combine with other particles to form various composite particles such as atoms and positronium, while neutrinos rarely interact with anything, and are consequently rarely observed. Wikipedia
INFO Two main classes of leptons exist, charged leptons (also known as the electron-like leptons), and neutral leptons (better known as neutrinos). Wikipedia
INFO In particle physics, a lepton is an elementary particle of half-integer spin (spin ​1⁄2) that does not undergo strong interactions. Wikipedia