 |
Quark Model
In particle physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks that give rise to the quantum numbers of the hadrons. The quark model underlies "flavor SU(3)", or the Eightfold Way, the successful classification scheme organizing the large number of lighter hadrons that were being discovered starting in the 1950s and continuing through the 1960s. It received experimental verification beginning in the late 1960s and is a valid and effective classification of them to date. The model was independently proposed by physicists Murray Gell-Mann, who dubbed them "quarks" in a concise paper, and George Zweig, who suggested "aces" in a longer manuscript. André Petermann also touched upon the central ideas from 1963 to 1965, without as much quantitative substantiation. Today, the model has essentially been absorbed as a component of the established quantum field theory of strong and electroweak particle interact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
 |
Standard Model
The Standard Model of particle physics is the Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the universe and classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists worldwide, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, proof of the top quark (1995), the tau neutrino (2000), and the Higgs boson (2012) have added further credence to the Standard Model. In addition, the Standard Model has predicted various properties of weak neutral currents and the W and Z bosons with great accuracy. Although the Standard Model is believed to be theoretically self-consistent and has demonstrated some success in providing experimental predictions, it leaves some physics be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
 |
Electric Charge
Electric charge (symbol ''q'', sometimes ''Q'') is a physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative''. Like charges repel each other and unlike charges attract each other. An object with no net charge is referred to as neutral particle, electrically neutral. Early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that do not require consideration of quantum mechanics, quantum effects. In an isolated system, the total charge stays the same - the amount of positive charge minus the amount of negative charge does not change over time. Electric charge is carried by subatomic particles. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the atomic nucleus, nuclei of atoms. If there are more electrons than protons in a piece of matter, it will have a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
 |
Top Quark
The top quark, sometimes also referred to as the truth quark, (symbol: t) is the most massive of all observed elementary particles. It derives its mass from its coupling to the Higgs field. This coupling is very close to unity; in the Standard Model of particle physics, it is the largest (strongest) coupling at the scale of the weak interactions and above. The top quark was discovered in 1995 by the CDF and DØ experiments at Fermilab. Like all other quarks, the top quark is a fermion with spin-1/2 and participates in all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. It has an electric charge of + ''e''. It has a mass of , which is close to the rhenium atom mass. The antiparticle of the top quark is the top antiquark (symbol: , sometimes called ''antitop quark'' or simply ''antitop''), which differs from it only in that some of its properties have equal magnitude but opposite sign. The top quark interacts ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
 |
Charm Quark
The charm quark, charmed quark, or c quark is an elementary particle found in composite subatomic particles called hadrons such as the J/psi meson and the charmed baryons created in particle accelerator collisions. Several bosons, including the W and Z bosons and the Higgs boson, can decay into charm quarks. All charm quarks carry Charm (quantum number), charm, a quantum number. This second-Generation (particle physics), generation particle is the third-most-massive quark, with a mass of as measured in 2022, and a charge of + Elementary charge, ''e''. The existence of the charm quark was first predicted by James Bjorken and Sheldon Glashow in 1964, and in 1970, Glashow, John Iliopoulos, and Luciano Maiani showed how its existence would account for experimental and theoretical discrepancies. In 1974, its existence was confirmed through the independent discoveries of the J/psi meson at Brookhaven National Laboratory and the Stanford Linear Accelerator Center. In the ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
|
Up Quark
The up quark or u quark (symbol: u) is the lightest of all quarks, a type of elementary particle, and a significant constituent of matter. It, along with the down quark, forms the neutrons (one up quark, two down quarks) and protons (two up quarks, one down quark) of atomic nucleus, atomic nuclei. It is part of the generation (physics), first generation of matter, has an electric charge of + elementary charge, ''e'' and a Quark#Mass, bare mass of . Like all quarks, the up quark is an elementary particle, elementary fermion with Spin (physics), spin spin-1/2, , and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the up quark is the up antiquark (sometimes called ''antiup quark'' or simply ''antiup''), which differs from it only in that some of its properties, such as electric charge, charge have additive inverse, equal magnitude but opposite sign. Its existence (along with that of the ... [...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] |
|
|
Charm (quantum Number)
Charm (symbol ''C'') is a flavour quantum number representing the difference between the number of charm quarks () and charm antiquarks () that are present in a particle: :C = n_\text - n_\ By convention, the sign of flavour quantum numbers agree with the sign of the electric charge carried by the quarks of corresponding flavour. The charm quark, which carries an electric charge (''Q'') of +, therefore carries a charm of +1. The charm antiquarks have the opposite charge (), and flavour quantum numbers (). As with any flavour-related quantum numbers, charm is preserved under strong and electromagnetic interaction, but not under weak interaction (see CKM matrix). For first-order weak decays, that is processes involving only one quark decay, charm can only vary by 1 (). Since first-order processes are more common than second-order processes (involving two quark decays), this can be used as an approximate "selection rule" for weak decays.Alexander BelyaeChapter 17 Weak Interactio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
|
 |
Strangeness
In particle physics, strangeness (symbol ''S'') is a property of particles, expressed as a quantum number, for describing decay of particles in strong and electromagnetic interactions that occur in a short period of time. The strangeness of a particle is defined as: S = -(n_\text - n_) where ''n'' represents the number of strange quarks () and ''n'' represents the number of strange antiquarks (). Evaluation of strangeness production has become an important tool in search, discovery, observation and interpretation of quark–gluon plasma (QGP). Strangeness is an excited state of matter and its decay is governed by CKM mixing. The terms ''strange'' and ''strangeness'' predate the discovery of the quark, and were adopted after its discovery in order to preserve the continuity of the phrase: strangeness of particles as −1 and anti-particles as +1, per the original definition. For all the quark flavour quantum numbers (strangeness, charm, topness and bottomness) the convent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
|
Isospin
In nuclear physics and particle physics, isospin (''I'') is a quantum number related to the up- and down quark content of the particle. Isospin is also known as isobaric spin or isotopic spin. Isospin symmetry is a subset of the flavour symmetry seen more broadly in the interactions of baryons and mesons. The name of the concept contains the term ''spin'' because its quantum mechanical description is mathematically similar to that of angular momentum (in particular, in the way it couples; for example, a proton–neutron pair can be coupled either in a state of total isospin 1 or in one of 0). But unlike angular momentum, it is a dimensionless quantity and is not actually any type of spin. Before the concept of quarks was introduced, particles that are affected equally by the strong force but had different charges (e.g. protons and neutrons) were considered different states of the same particle, but having isospin values related to the number of charge states. A close exami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
|
|
Flavour Quantum Numbers
In particle physics, flavour or flavor refers to the ''species'' of an elementary particle. The Standard Model counts six flavours of quarks and six flavours of leptons. They are conventionally parameterized with ''flavour quantum numbers'' that are assigned to all subatomic particles. They can also be described by some of the family symmetries proposed for the quark-lepton generations. Quantum numbers In classical mechanics, a force acting on a point-like particle can only alter the particle's dynamical state, i.e., its momentum, angular momentum, etc. Quantum field theory, however, allows interactions that can alter other facets of a particle's nature described by non-dynamical, discrete quantum numbers. In particular, the action of the weak force is such that it allows the conversion of quantum numbers describing mass and electric charge of both quarks and leptons from one discrete type to another. This is known as a flavour change, or flavour transmutation. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
|
|
C-symmetry
In physics, charge conjugation is a transformation that switches all particles with their corresponding antiparticles, thus changing the sign of all charges: not only electric charge but also the charges relevant to other forces. The term C-symmetry is an abbreviation of the phrase "charge conjugation symmetry", and is used in discussions of the symmetry of physical laws under charge-conjugation. Other important discrete symmetries are P-symmetry (parity) and T-symmetry (time reversal). These discrete symmetries, C, P and T, are symmetries of the equations that describe the known fundamental forces of nature: electromagnetism, gravity, the strong and the weak interactions. Verifying whether some given mathematical equation correctly models nature requires giving physical interpretation not only to continuous symmetries, such as motion in time, but also to its discrete symmetries, and then determining whether nature adheres to these symmetries. Unlike the continuous symmetri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |