| Standard Model |
Article Index for Standard Model |
Articles about Standard Model |
Website Links For Standard Model |
Information AboutStandard Model |
| CATEGORIES ABOUT STANDARD MODEL | |
| fundamental physics concepts | |
| particle physics | |
| standard modelfundamental physics concepts | |
| particle physics | |
| standard model | |
| particle physics | |
| quantum field theory | |
|
The Standard Model of Particle Physics is a theory which describes three of the four known Fundamental Interaction s between the Elementary Particles that make up all Matter . It is a Quantum Field Theory developed between 1970 and 1973 which is consistent with both Quantum Mechanics and Special Relativity . To date, almost all experimental tests of the three forces described by the Standard Model have agreed with its predictions. However, the Standard Model falls short of being a Complete Theory Of Fundamental Interactions , primarily because of its lack of inclusion of Gravity , the fourth known fundamental interaction, but also because of the large number of numerical parameters (such as masses and coupling constants) that must be put "by hand" into the theory (rather than being derived from first principles). __TOC__ THE STANDARD MODEL In physics, the dynamics of both matter and energy in Nature is presently best understood in terms of the kinematics and interactions of Fundamental Particle s. To date, science has managed to reduce the Laws which seem to govern the behavior and interaction of all types of matter and energy we are aware of, to a small core of fundamental laws and theories. A major goal of physics is to find the 'common ground' that would unite all of these into one Integrated Model Of Everything , in which all the other laws we know of would be special cases, and from which the behavior of all matter and energy can be derived (ideally from First Principles ). Within this, the Standard Model is a grouping of two major theories – Quantum Electroweak and Quantum Chromodynamics – which provides an internally consistent theory describing interactions between all experimentally observed particles. Technically, Quantum Field Theory provides the mathematical framework for the Standard Model. The Standard Model describes each type of particle in terms of a mathematical Field . For a technical description of the fields and their interactions, see Standard Model (basic Details) . For ease of description, the Standard Model can be divided into three parts – covering particles of matter, force mediating particles, and the Higgs Boson . Particles of Matter The matter particles described by the Standard Model all have an intrinsic property known as ' Spin ' whose value is determined to be 1/2. In Standard Model terms, this means that all matter particles are Fermions . For this reason, they follow the Pauli Exclusion Principle in accordance with the Spin-statistics Theorem , and it is this which causes their 'material' quality. Apart from their Antiparticle partners, a total of twelve different types of matter particles are known and accounted for by the Standard Model. Six of these are classified as Quarks ( Up , Down , Strange , Charm , Top and Bottom ), and the other six as Leptons ( Electron , Muon , Tau , and their corresponding Neutrino s). Matter particles also carry Charges which make them susceptible to the Fundamental Force s, which are in turn mediated as described in the next subsection.
Pairs from each group (one up-type quark, one down-type quark, a down-type lepton and its corresponding neutrino) form what is known as a ' Generation '. The corresponding particles between each generation are identical to each other, with the exception of their Mass and a property known as their Flavor . Force-Mediating Particles Forces in physics are the ways that particles interact and influence each other. At a macro level, for example, the Electromagnetic Force allows particles to interact with, and via, Magnetic Field s, and the force of Gravitation allows two particles with mass to attract one another in accordance with Newton's Law Of Gravitation . The standard model explains such forces as resulting from matter particles exchanging other particles, known as force-mediating particles. When a force-mediating particle is exchanged, at a macro level the effect is equivalent to a force influencing both of them, and the particle is therefore said to have ''mediated'' (i.e., been the agent of) that force. Force-mediating particles are believed to be the reason why the forces and interactions between particles observed in the laboratory and in the universe exist. The force-mediating particles described by the Standard Model also all have spin (as did matter particles), but in their case, the value of the spin is 1, meaning that all force-mediating particles are Bosons . As a result, they do not follow the Pauli Exclusion Principle . The different types of force mediating particles are described below.
The interactions between all the particles described by the Standard Model are summarized in the illustration immediately above and to the right. The Higgs Boson See Also: Higgs Boson The Higgs particle is a hypothetical massive Scalar Elementary Particle predicted by the Standard Model, and the only fundamental particle predicted by that model which has not fully been observed as yet. This is partly because it requires an exceptionally large amount of Energy to create and observe under laboratory circumstances. It has no intrinsic spin, and thus (like the force-mediating particles) is also classified as a boson. The Higgs Boson plays a unique role in the Standard Model, and a key role in explaining the origins of the Mass of other elementary particles, in particular the difference between the massless Photon and the very heavy W And Z Bosons . Elementary particle masses, and the differences between Electromagnetism (caused by the photon) and the Weak Force (caused by the W and Z bosons), are critical to many aspects of the structure of microscopic (and hence macroscopic) matter; thus, if it is proven to exist, the Higgs boson has an enormous effect on the world around us. As Of 2007 , no experiment has directly detected the existence of the Higgs boson, but there is some indirect evidence for it. It is hoped that upon the completion of the Large Hadron Collider , experiments conducted at CERN would bring experimental evidence confirming the existence for the particle. List of Standard Model Fermions This table is based in part on data gathered by the Particle Data Group ().
| |||||||
| !colspan | "8"  |
||||||
| !colspan | "8" style="background:#ffdead"Generation 2 |
||||||
| -style | "background:#ffdddd" |
||||||
| style | "background:#efefef" Muon |
||||||
| style | "background:#efefef" Antimuon |
||||||
| style | "background:#efefef" Muon-neutrino |
||||||
| style | "background:#efefef" Charm Quark |
||||||
| style | "background:#efefef" Charm Antiquark |
|