In particle physics, the elementary particles or fundamental particles are particles without substructure, so they are not composed of other particles. Particles currently considered elementary include fundamental fermions (quarks, leptons, antiquarks, and antileptons), which are generally "matter particles" and "antimatter particles", as well as the fundamental bosons (gauge bosons and Higgs bosons), which are generally " particles of force "that mediate the interaction between fermions. A particle containing two or more elementary particles is a composite particle .
The everyday matter consists of atoms, which were once thought to be elementary particles of matter - atoms meaning "can not cut" in Greek - although the existence of atoms remained controversial until about 1910, as some prominent physicists assume molecule. as a mathematical illusion, and matter that eventually consists of energy. Immediately, the subatomic constituents of the atom are identified. When the 1930s were opened, electrons and protons had been observed, along with photons, particles of electromagnetic radiation. At that time, the emergence of quantum mechanics has recently radically altered the conception of particles, since single particles may appear to encompass the field as well as waves, a paradox still avoiding a satisfactory explanation.
Through quantum theory, protons and neutrons are found to contain quark-up quarks and down quarks - now regarded as elementary particles. And in a molecule, three degrees of freedom of electrons (charge, rotation, orbitals) can be separated by wave function into three quasiparticles (holon, spinon, orbiton). But the free electrons - which do not orbit the nucleus of the atom and have no orbital motion - appear unmovable and still be considered as fundamental particles.
Around 1980, the status of elementary particles as the main substituents (substituents) - was largely discarded for a more practical view, embodied in the Standard Model of particle physics, known as the most successful scientific experiment in the field of science. theory. Many elaborations and theories outside the Standard Model, including popular supersymmetry, double the number of elementary particles by hypothesizing that any known particle with a "shadow" partner is much more massive, even though all of the superpartners are still missing. Meanwhile, the basic boson that mediates gravity - gravitons - remains hypothetical.
Video Elementary particle
Ikhtisar
All the basic particles - depending on their spin - either boson or fermion. This is distinguished through spin-theorem statistical statistics. Spinning half-integer particles show Fermi-Dirac statistics and is a fermion. The integer integer rotates, in other words full-integer, showing Bose-Einstein and boson statistics.
Note:
1. Antielectron (
e < br> ) is traditionally called a positron.
2. The known boson power carriers all have spin = 1 and therefore vector bosons. The hypothetical graviton has spin = 2 and is a tensor boson; whether it's a gauge boson, too, is unknown.
In the Standard Model, elementary particles are represented for predictive utility as point particles. Despite its great success, the Standard Model is limited to the microcosm by its gravitational negligence and has several parameters arbitrarily added but can not be explained.
Maps Elementary particle
Basic common particles
According to the current big bang nucleosynthesis model, the primordial composition of matter seen in the universe should be about 75% hydrogen and 25% helium-4 (in mass). Neutrons consist of one up and two under quarks, while protons are made of two and one down quarks. Since other common base particles (such as electrons, neutrinos, or weak bosons) are very light or very rare when compared to atomic nuclei, we can ignore their mass contribution to the observable total mass of the universe. Therefore, it can be concluded that most of the visible mass of the universe consists of protons and neutrons, which, like all baryons, in turn comprise quarks and bottom quarks.
Some estimates suggest that there are about 10 80 baryon (almost all protons and neutrons) in the observed universe.
The number of protons in the observable universe is called the Eddington number.
In terms of the number of particles, some estimates imply that almost all matter, excluding dark matter, takes place in neutrinos, and that approximately 10 86 elementary particles of matter exist in the universe looks, mostly neutrinos. Another estimate implies that approximately 10 97 elementary particles exist in the visible universe (excluding dark matter), mostly photons and other massless carrier forces.
Standard Model
The Standard particle physics model contains 12 basic fermion flavors, plus the corresponding antiparticles, as well as a basic boson that mediates Higgs strength and bosons, reported on July 4, 2012, as they may be detected by two parent pilots at the Large Hadron Collider (ATLAS and CMS). However, the Standard Model is widely regarded as a provisional theory rather than a truly fundamental one, since it is unknown whether it is compatible with Einstein's general relativity. There may be hypothetical base particles not described by the Standard Model, such as gravitons, particles that will carry gravitational forces, and sparticles, supersymmetric pairs of ordinary particles.
Basic foundations
12 base fermions are divided into 3 generations of 4 particles each. Half of the fermions are leptons, three of which have electric charges -1, called electrons (
e - ), muon (
? - ), and tau ( > ? - , the other three leptons are neutrinos (
e ,
?
? ), which is a fermion th no electric or color charge The remaining six particles are quarks (discussed below). Generation
Mass
The following table lists the current measured mass and mass forecast for all fermions, using the same measurement scale: millions of electrons-volt (MeV). For example, the most well known quark mass is the top quark (
t
) at 172,7Ã, GeV/cÃ,² or 172 700 MeV/c², is estimated using the On-shell scheme.
The estimates of quark mass values ​​depend on the quantum chromodynamic version used to describe quark interactions. Quarks are always confined in a gluon envelope that gives a much larger mass to the mesons and baryons where quarks occur, so the values ​​for quark mass can not be measured directly. Because their mass is very small compared to the effective mass of the surrounding gluons, small differences in computations make a huge difference in mass.
Antiparticles
There are also 12 fundamental fermionic antiparticles that correspond to these 12 particles. For example, antielectron (positron)
e is an electron antiparticle and has an electric charge of 1.
Quarks
Quarks are isolated and antiquarks are never detected, facts explained by confinement. Each quark carries one of three color charges of strong interaction; same antiquarks carries anticolor. The charged-colored particles interact through the exchange of gluon in the same way as charged particles interact through the exchange of photons. However, the gluon itself is colorful, generating strong power amplification as charged charged color particles. Unlike the electromagnetic force, which diminishes when the particles are charged separately, the charged charged particles feel an increase in strength.
However, charged-colored particles can combine to form neutral color composite particles called hadrons. A quark can be paired with antiquark: the quark has a color and the antiquark has an appropriate anticolor. Color and anticolor cancel, forming neutral meson colors. Alternatively, three quarks can exist together, one is a "red" quark, the other "blue", the other "green". These three colored quarks form a neutral color baryon. Symmetrically, three antiquarks of "antired", "antiblue" and "antigreen" colors can form neutral color antibodies.
Quarks also carry fractional electrical charges, but, since they are confined in hadrons whose loads are all integral, the fractional charge is never isolated. Note that the quark has an electrical charge of either / 3 or - 1 / 3 , whereas the antiquarks have a corresponding good electrical charge - / 3 or 1 / 3 .
The evidence for quarks comes from deep inelastic scattering: firing electrons at the core to determine the charge distribution in the nucleons (the baryons). If the charge is uniform, the electric field around the proton must be uniform and the electrons will spread elastically. Low-energy electrons spread in this way, but, above a certain energy, protons deflect several electrons through a large angle. The recoiling electrons have less energy and emitted emitted particles. This inelastic scatter indicates that the charge in the proton is not uniform but is divided among the smaller charged particles: quarks.
Fundamental boson
In the Standard Model, boson (spin-1) models (gluons, photons, and W and Z bosses) mediate forces, while the Higgs (spin-0) boson is responsible for the intrinsic particle mass. Bosons differ from fermions in the fact that some bosons can occupy the same quantum state (Pauli exclusion principle). Also, the boson can be a base, like a photon, or a combination, like a meson. Spin boson is an integer instead of half an integer.
Gluons
Gluons mediate strong interactions, which join quarks and thus form the hadron, which is either baryon (three quarks) or mesons (one quark and one antiquark). Protons and neutrons are baryons, joining gluons to form an atomic nucleus. Like quarks, gluons show off color and anticolor - unrelated to the concept of visual color - sometimes in combination, all eight variations of gluon.
boson Electroweak
There are three weak measuring bosons: W , W - , and Z 0 ; this mediates weak interactions. The W bosons are known for their mediation in nuclear decay. The W - converts a neutron into a proton and then decomposes into an electron and an antineutrino electron pair. Z 0 did not convert the load but changed the momentum and was the only mechanism for elastic neutrino dissipation. The weak gauge bosons are found because of the momentum changes in electrons from the Z-neutrino exchange. Photons without mass mediate electromagnetic interactions. These four measuring bosons form an electrolyte interaction between the basic particles.
Higgs boson
Although the weak and electromagnetic forces appear very different to us in everyday energies, the two forces are theorized to unite as single electro forces at high energy. This prediction is clearly confirmed by cross-sectional measurements for scattering high-energy electrons on the HERA collider at DESY. The difference in low energy is a consequence of the high mass of the boss W and Z , which in turn is a consequence of the Higgs mechanism. Through the process of breaking spontaneous symmetry, Higgs chooses a special direction in the electrolyte chamber which causes the three electroweak particles to become very heavy (weak bosons) and the other remains massless (photons). On July 4, 2012, after years of experimenting searching for evidence of its existence, the Higgs boson was announced to have been observed at the CERN Large Hadron Collider. Peter Higgs who first suggested the existence of the Higgs boson was present at the announcement. Higgs bosons are believed to have a mass of about 125 GeV. The statistical significance of the present invention is reported as 5-sigma, which implies a certainty of about 99.99994%. In particle physics, this is the level of significance necessary to formally label experimental observations as invention. Research on the properties of newly discovered particles continues.
Graviton
Graviton is a hypothetical base spin-2 particle proposed to mediate gravity. Although it remains undiscovered due to the inherent difficulty of detection, it is sometimes included in the basic particle table. Conventional gravitons do not have mass, although there are models that contain a very large Kaluza-Klein gravity.
Beyond Model Standard
Although the experimental evidence strongly confirms predictions derived from the Standard Model, some parameters are arbitrarily added, not determined by any particular explanation, which remains a mystery, for example a hierarchy problem. The theory beyond the Standard Model's attempt to overcome this deficiency.
Grand unification
One extension of the Standard Model tries to combine electro-leak interaction with strong interaction into a single 'unified theory' (GUT). Such a force will spontaneously be broken down into three forces by mechanisms such as Higgs. The most dramatic predictions of the great unification are the existence of the bosses X and Y, which lead to the decay of protons. However, non-observation of proton decay at the Super-Kamiokande neutrino observatory put aside the simplest GUTs, including SU (5) and SO (10).
Supersymmetry
Supersymmetry extends the Standard Model by adding another symmetry class to the Lagrangian. This symmetry exchange the fermionic particles with the bosonic. This symmetry predicts the existence of supersymmetric particles, abbreviated as sparticles , which include sleepingons, squark, neutralinos, and charginos. Each particle in the Standard Model will have a spin different superpartner with 1 / 2 of the regular particle. Due to the breakup of supersymmetry, sparticles are much heavier than their common counterparts; they are so heavy that the existing particle collider will not be strong enough to produce it. However, some physicists believe that the spartikel will be detected by the Large Hadron Collider at CERN.
String theory
String theory is a model of physics in which all the "particles" that make up matter are composed of strings (measuring at Planck's length) that are in 11-dimensions (according to M-theory, leading version) or 12-dimensional (according to F-theory) universe. These strings vibrate at different frequencies that determine mass, electric charge, color charge, and rotation. Strings can open (line) or closed in a circle (one-dimensional sphere, like a circle). As the rope moves through the space it sweeps away the so-called sheets of the world . The string theory predicts 1- to 10-brane (bran-1 being a string and 10-brane into a 10-dimensional object) that prevents tears in the "fabric" of space using the principle of uncertainty (eg electrons orbiting hydrogen atoms have the probability, so it can be elsewhere in the universe at any given moment).
The string theory suggests that our universe is just a 4-brane, in which there are three dimensions of space and dimension 1 time that we observe. The remaining six theoretical dimensions are very small and huddled (and too small to be accessed macroscopically) or absent in our universe (because they exist in a magnificent scheme called "multiverse" outside our known universe).
Some of the predictions of string theory include the existence of very massive regular particles because of the excitation vibrations of the fundamental strings and the presence of spin-2 particles without mass behaving like gravitons.
Technicolor
Technicolor Theory attempts to modify the Standard Model in a minimal way by introducing interactions such as the new QCD. This means one adds a new theory called Techniquarks, interacting through so-called Technigluons. The main idea is that Higgs-Boson is not a basic particle but is a bonded state of these objects.
Preon Theory
According to the theory of preons there are one or more orders of particles that are more basic than those (or most of them) found in the Standard Model. The most basic of these are usually called preons, which come from "pre-quark". In essence, the theory of preons tries to make the Standard Model what the Standard Model does for zoos of previously emerging particles. Most models assume that almost everything in the Standard Model can be explained in three to half a dozen more fundamental particles and rules governing their interactions. Interest in prey has diminished since the simplest model was experimentally ruled out in the 1980s.
Acceleration theory
The accelerator is a hypothetical subatomic particle that connects integrally the newly discovered mass of neutrinos to the dark energy that allegedly accelerates the expansion of the universe.
The most important address of current experimental and theoretical knowledge about elementary particle physics is the Particle Data Group, where different international institutions collect all experimental data and provide a brief overview of contemporary theoretical understandings.
- The Particle Data Group
other pages are:
- Greene, Brian, " Basic Particle ", The Elegant Universe, NOVA (PBS)
- particleadventure.org, a well-made introduction also for non-physicists
- CERNCourier: Higgs and melodrama season
- Pentaquark information page
- Interactions.org, particle physics news
- Symmetry Magazine, Fermilab/SLAC publication
- "Sized Matter: extreme occult perception", Michigan University project for artistic visualization of subatomic particles
- The Basic Particle made sense, interactive visualization allows physical properties to be compared
Source of the article : Wikipedia
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