This is a timeline of subatomic particle discoveries, including all particles thus far discovered which appear to be elementary(that is, indivisible) given the best available evidence. It also includes the discovery of composite particles and antiparticles that were of particular historical importance.
More specifically, the inclusion criteria are:
- Elementary particles from the Standard Model of particle physics that have so far been observed. The Standard Model is the most comprehensive existing model of particle behavior. All Standard Model particles including the Higgs boson have been verified, and all other observed particles are combinations of two or more Standard Model particles.
- Antiparticles which were historically important to the development of particle physics, specifically the positron and antiproton. The discovery of these particles required very different experimental methods from that of their ordinary matter counterparts, and provided evidence that all particles had antiparticles—an idea that is fundamental to quantum field theory, the modern mathematical framework for particle physics. In the case of most subsequent particle discoveries, the particle and its anti-particle were discovered essentially simultaneously.
- Composite particles which were the first particle discovered containing a particular elementary constituent, or whose discovery was critical to the understanding of particle physics.
| Time | Event |
|---|---|
| 1800 | William Herschel discovers "heat rays" |
https://en.wikipedia.org/wiki/Timeline_of_particle_discoveries
In physics, polaritons /pəˈlærɪtɒnz, poʊ-/[1] are quasiparticles resulting from strong coupling of electromagnetic waves with an electric or magnetic dipole-carrying excitation.[example needed] They are an expression of the common quantumphenomenon known as level repulsion, also known as the avoided crossing principle. Polaritons describe the crossing of the dispersion of light with any interacting resonance. To this extent polaritons can also be thought as the new normal modes of a given material or structure arising from the strong coupling of the bare modes, which are the photon and the dipolar oscillation. The polariton is a bosonic quasiparticle, and should not be confused with the polaron (a fermionicone), which is an electron plus an attached phonon cloud.
Whenever the polariton picture is valid (i.e. when the weak coupling limit is an invalid approximation), the model of photons propagating freely in crystals is insufficient. A major feature of polaritons is a strong dependency of the propagation speed of light through the crystal on the frequency of the photon. For exciton-polaritons, rich experimental results on various aspects have been gained in copper(I) oxide.
https://en.wikipedia.org/wiki/Polariton
In physics, a plasmon is a quantum of plasma oscillation. Just as light (an optical oscillation) consists of photons, the plasma oscillation consists of plasmons. The plasmon can be considered as a quasiparticle since it arises from the quantization of plasma oscillations, just like phonons are quantizations of mechanical vibrations. Thus, plasmons are collective (a discrete number) oscillations of the free electron gasdensity. For example, at optical frequencies, plasmons can couple with a photon to create another quasiparticle called a plasmon polariton.
https://en.wikipedia.org/wiki/Plasmon
In physics, a plasmaron is a quasiparticle arising in a system that has strong plasmon-electron interactions. It is a quasiparticle formed by quasiparticle-quasiparticle interactions, since both plasmons and electron holes are collective modes of different kinds. It has recently been observed in graphene and earlier in elemental bismuth.[1][2]
https://en.wikipedia.org/wiki/Plasmaron
A trion is a localized excitation which consists of three charged particles. A negative trion consists of two electrons and one hole and a positive trion consists of two holes and one electron. The trion itself is a quasiparticle and is somewhat similar to an exciton, which is a complex of one electron and one hole. The trion has a ground singlet state (spin s = 1/2) and an excited triplet state (s = 3/2). Here singlet and triplet degeneracies originate not from the whole system but from the two identical particles in it. The half-integer spin value distinguishes trions from excitons in many phenomena; for example, energy states of trions, but not excitons, are split in an applied magnetic field. Trion states were predicted theoretically in 1958;[1] they were observed experimentally in 1993 in CdTe/Cd1−xZnxTe quantum wells,[2] and later in various other optically excited semiconductor structures.[3][4] There are experimental proofs of their existence in nanotubes[5] supported by theoretical studies.[6] Despite numerous reports of experimental trion observations in different semiconductor heterostructures, there are serious concerns on the exact physical nature of the detected complexes. The originally foreseen 'true' trion particle has a delocalized wavefunction (at least at the scales of several Bohr radii) while recent studies reveal significant binding from charged impurities in real semiconductor quantum wells.[7]
Trions have been observed in atomically thin two-dimensional (2D) transition-metal dichalcogenide semiconductors.[8][9] In 2D materials the form of the interaction between charge carriers is modified by the nonlocal screening provided by the atoms in the layer. The interaction is approximately logarithmic at short range and of Coulomb 1/r form at long range.[10] The diffusion Monte Carlo method has been used to obtain numerically exact results for the binding energies of trions in 2D semiconductors within the effective mass approximation.[11][12][13]
https://en.wikipedia.org/wiki/Trion_(physics)
In particle theory, the skyrmion (/ˈskɜːrmi.ɒn/) is a topologically stable field configuration of a certain class of non-linear sigma models. It was originally proposed as a model of the nucleon by (and named after) Tony Skyrme in 1961.[1][2][3][4] As a topological soliton in the pion field, it has the remarkable property of being able to model, with reasonable accuracy, multiple low-energy properties of the nucleon, simply by fixing the nucleon radius. It has since found application in solid-state physics, as well as having ties to certain areas of string theory.
Skyrmions as topological objects are important in solid-state physics, especially in the emerging technology of spintronics. A two-dimensional magnetic skyrmion, as a topological object, is formed, e.g., from a 3D effective-spin "hedgehog" (in the field of micromagnetics: out of a so-called "Bloch point" singularity of homotopy degree +1) by a stereographic projection, whereby the positive north-pole spin is mapped onto a far-off edge circle of a 2D-disk, while the negative south-pole spin is mapped onto the center of the disk. In a spinor field such as for example photonic or polariton fluids the skyrmion topology corresponds to a full Poincaré beam[5] (which is, a quantum vortex of spin comprising all the states of polarization).[6]
Skyrmions have been reported, but not conclusively proven, to be in Bose–Einstein condensates,[7] thin magnetic films[8] and in chiral nematic liquid crystals.[9]
As a model of the nucleon, the topological stability of the skyrmion can be interpreted as a statement that the baryon number is conserved; i.e. that the proton does not decay. The Skyrme Lagrangian is essentially a one-parameter model of the nucleon. Fixing the parameter fixes the proton radius, and also fixes all other low-energy properties, which appear to be correct to about 30%. It is this predictive power of the model that makes it so appealing as a model of the nucleon.
Hollowed-out skyrmions form the basis for the chiral bag model (Cheshire Cat model) of the nucleon. Exact results for the duality between the fermion spectrum and the topological winding number of the non-linear sigma model have been obtained by Dan Freed. This can be interpreted as a foundation for the duality between a quantum chromodynamics (QCD) description of the nucleon (but consisting only of quarks, and without gluons) and the Skyrme model for the nucleon.
The skyrmion can be quantized to form a quantum superposition of baryons and resonance states.[10] It could be predicted from some nuclear matter properties.[11]
https://en.wikipedia.org/wiki/Skyrmion
In particle physics hexaquarks, alternatively known as sexaquarks,[1] are a large family of hypothetical particles, each particle consisting of six quarks or antiquarks of any flavours. Six constituent quarks in any of several combinations could yield a colour charge of zero; for example a hexaquark might contain either six quarks, resembling two baryons bound together (a dibaryon), or three quarks and three antiquarks.[2] Once formed, dibaryons are predicted to be fairly stable by the standards of particle physics.
A number of experiments have been suggested to detect dibaryon decays and interactions. In the 1990s, several candidate dibaryon decays were observed but they were not confirmed.[3][4][5]
There is a theory that strange particles such as hyperons[6] and dibaryons[7] could form in the interior of a neutron star, changing its mass–radius ratio in ways that might be detectable. Accordingly, measurements of neutron stars could set constraints on possible dibaryon properties.[8] A large fraction of the neutrons in a neutron star could turn into hyperons and merge into dibaryons during the early part of its collapse into a black hole[citation needed]. These dibaryons would very quickly dissolve into quark–gluon plasma during the collapse, or go into some currently unknown state of matter.
https://en.wikipedia.org/wiki/Hexaquark
A superatom is any cluster of atoms that seem to exhibit some of the properties of elemental atoms.
Sodium atoms, when cooled from vapor, naturally condense into clusters, preferentially containing a magic number of atoms (2, 8, 20, 40, 58, etc.), with the outermost electron of each atom entering an orbital encompassing all the atoms in the cluster. Superatoms tend to behave chemically in a way that will allow them to have a closed shell of electrons, in this new counting scheme.[citation needed]
https://en.wikipedia.org/wiki/Superatom
Protonium (symbol: Pn), also known as antiprotonic hydrogen, is a type of exotic atom in which a proton (symbol: p) and an antiproton (symbol: p) orbit each other.[1] Since protonium is a bound system of a particle and its corresponding antiparticle, it is an example of a type of exotic atom called an onium.
Protonium has a mean lifetime of approximately 1.0 μs and a binding energy of −0.75 keV.[2]
Like all onia, protonium is a boson with all quantum numbers (baryon number, flavour quantum numbers, etc.) and electrical chargeequal to 0.
https://en.wikipedia.org/wiki/Protonium
Positronium (Ps) is a system consisting of an electron and its anti-particle, a positron, bound together into an exotic atom, specifically an onium. The system is unstable: the two particles annihilate each other to predominantly produce two or three gamma-rays, depending on the relative spin states. The energy levels of the two particles are similar to that of the hydrogen atom (which is a bound state of a proton and an electron). However, because of the reduced mass, the frequencies of the spectral lines are less than half of those for the corresponding hydrogen lines.
https://en.wikipedia.org/wiki/Positronium
Hydrogen (1H) has three naturally occurring isotopes, sometimes denoted 1H, 2H, and 3H. The first two of these are stable, while 3H has a half-life of 12.32 years. There are also heavier isotopes, which are all synthetic and have a half-life less than one zeptosecond (10−21 second). Of these, 5H is the most stable, and 7H is the least.[1][2]
Hydrogen is the only element whose isotopes have different names in common use today: the 2H (or hydrogen-2) isotope is deuterium[3] and the 3H (or hydrogen-3) isotope is tritium.[4] The symbols D and T are sometimes used for deuterium and tritium. The IUPAC accepts the D and T symbols, but recommends instead using standard isotopic symbols (2H and 3H) to avoid confusion in the alphabetic sorting of chemical formulas.[5] The ordinary isotope of hydrogen, with no neutrons, is sometimes called protium.[6] (During the early study of radioactivity, some other heavy radioactive isotopes were given names, but such names are rarely used today.)
https://en.wikipedia.org/wiki/Isotopes_of_hydrogen#Hydrogen-1_(protium)
In particle physics, a lepton is an elementary particle of half-integer spin (spin 1⁄2) that does not undergo strong interactions.[1] Two main classes of leptons exist: chargedleptons (also known as the electron-like leptons or muons), and neutral leptons (better known as neutrinos). 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. The best known of all leptons is the electron.
There are six types of leptons, known as flavours, grouped in three generations.[2] The first-generation leptons, also called electronic leptons, comprise the electron (
e−
) and the electron neutrino (
ν
e); the second are the muonic leptons, comprising the muon (
μ−
) and the muon neutrino (
ν
μ); and the third are the tauonic leptons, comprising the tau (
τ−
) and the tau neutrino (
ν
τ). Electrons have the least mass of all the charged leptons. 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. 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).
Leptons have various intrinsic properties, including electric charge, spin, and mass. 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, of which the latter is proportional to charge, and is thus zero for the electrically neutral neutrinos.
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. According to certain theories, neutrinos may be their own antiparticle. It is not currently known whether this is the case.
The first charged lepton, the electron, was theorized in the mid-19th century by several scientists[3][4][5] and was discovered in 1897 by J. J. Thomson.[6] The next lepton to be observed was the muon, discovered by Carl D. Anderson in 1936, which was classified as a meson at the time.[7] After investigation, it was realized that the muon did not have the expected properties of a meson, but rather behaved like an electron, only with higher mass. It took until 1947 for the concept of "leptons" as a family of particles to be proposed.[8] The first neutrino, the electron neutrino, was proposed by Wolfgang Pauli in 1930 to explain certain characteristics of beta decay.[8] It was first observed in the Cowan–Reines neutrino experiment conducted by Clyde Cowan and Frederick Reines in 1956.[8][9] The muon neutrino was discovered in 1962 by Leon M. Lederman, Melvin Schwartz, and Jack Steinberger,[10] and the tau discovered between 1974 and 1977 by Martin Lewis Perl and his colleagues from the Stanford Linear Accelerator Center and Lawrence Berkeley National Laboratory.[11] The tau neutrino remained elusive until July 2000, when the DONUT collaboration from Fermilab announced its discovery.[12][13]
Leptons are an important part of the Standard Model. Electrons are one of the components of atoms, alongside protons and neutrons. Exotic atoms with muons and taus instead of electrons can also be synthesized, as well as lepton–antilepton particles such as positronium.
 Leptons are involved in several processes such as beta decay. | |
| Composition | Elementary particle |
|---|---|
| Statistics | Fermionic |
| Generation | 1st, 2nd, 3rd |
| Interactions | Electromagnetism, Gravitation, Weak |
| Symbol | ℓ |
| Antiparticle | Antilepton ( ℓ ) |
| Types | 6 (electron, electron neutrino, muon, muon neutrino, tau, tau neutrino) |
| Electric charge | +1 e, 0 e, −1 e |
| Color charge | No |
| Spin | 1⁄2 |
| Fermion categories | Elementary particle generation | |||
|---|---|---|---|---|
| Type | Subtype | First | Second | Third |
| Quarks (colored) | down-type | down | strange | bottom |
| up-type | up | charm | top | |
| Leptons (color-free) | charged | electron | muon | tauon |
| neutral | electron neutrino | muon neutrino | tau neutrino | |
https://en.wikipedia.org/wiki/Lepton
A scalar boson is a boson whose spin equals zero.[1] Boson means that the particle's wavefunction is symmetric under particle exchange and therefore follows Bose–Einstein statistics. The spin-statistics theorem implies that all bosons have an integer-valued spin;[2] the scalar fixes this value to zero.
The name scalar boson arises from quantum field theory, which demands that fields of spin-zero particles transform like a scalar under Lorentz transformation (i.e. are Lorentz invariant).
A pseudoscalar boson is a scalar boson that has odd parity, whereas "regular" scalar bosons have even parity.[3]
https://en.wikipedia.org/wiki/Scalar_boson
In particle physics, a gauge boson is a bosonic elementary particle that mediates interactions among elementary fermions, and thus acts as a force carrier. Gauge bosons can carry any of the four fundamental interactions of nature.[1][2] Elementary particles, whose interactions are described by a gauge theory, interact with each other by the exchange of gauge bosons; usually as virtual particles.
Photons, W and Z bosons, gluons, and the hypothetical gravitons are gauge bosons. All known gauge bosons have a spin of 1; for comparison, the Higgs boson has spin zero. Therefore, all known gauge bosons are vector bosons.
Gauge bosons are different from the other kinds of bosons: first, fundamental scalar bosons (the Higgs boson); second, mesons, which are compositebosons, made of quarks; third, larger composite, non-force-carrying bosons, such as certain atoms.
https://en.wikipedia.org/wiki/Gauge_boson
In particle physics, for models with N=1 supersymmetry a higgsino, symbol
H͂
, is the superpartner of the Higgs field. A higgsino is a Dirac fermionic field with spin 1⁄2 and it refers to a weak isodoublet with hypercharge half under the Standard Model gauge symmetries. After electroweak symmetry breaking higgsino fields linearly mix with U(1) and SU(2) gauginos leading to four neutralinos and two charginos[1] that refer to physical particles. While the two charginos are charged Dirac fermions (plus and minus each), the neutralinos are electrically neutral Majorana fermions. In an R-parity-conserving version of the Minimal Supersymmetric Standard Model, the lightest neutralino typically becomes the lightest supersymmetric particle (LSP). The LSP is a particle physics candidate for the dark matter of the universe since it cannot decay to particles with lighter mass. A neutralino LSP, depending on its composition can be bino, wino or higgsino dominated in nature[2] and can have different zones of mass values in order to satisfy the estimated dark matter relic density. Commonly, a higgsino dominated LSP is often referred as a higgsino, in spite of the fact that a higgsino is not a physical state in the true sense.
https://en.wikipedia.org/wiki/Higgsino
In supersymmetric extension to the Standard Model of physics, a sfermion is a hypothetical spin-0 superpartner particle (sparticle) of its associated fermion.[1][2] Each particle has a superpartner with spin that differs by 12. Fermions in the SM have spin-12 and, therefore, sfermions have spin 0.[3][4]
The name 'sfermion' was formed by the general rule of prefixing an 's' to the name of its superpartner, denoting that it is a scalar particle with spin 0. For instance, the electron's superpartner is the selectron and the top quark's superpartner is the stop squark.
One corollary from supersymmetry is that sparticles have the same gauge numbers as their SM partners. This means that sparticle–particle pairs have the same color charge, weak isospin charge, and hypercharge (and consequently electric charge). Unbroken supersymmetry also implies that sparticle–particle pairs have the same mass. This is evidently not the case, since these sparticles would have already been detected. Thus, sparticles must have different masses from the particle partners and supersymmetry is said to be broken.[5][6]
https://en.wikipedia.org/wiki/Sfermion
https://en.wikipedia.org/wiki/Photino
https://en.wikipedia.org/wiki/Majorana_fermion
https://en.wikipedia.org/wiki/Antineutron
https://en.wikipedia.org/wiki/Antiproton
https://en.wikipedia.org/wiki/Lambda_baryon
https://en.wikipedia.org/wiki/Delta_baryon
https://en.wikipedia.org/wiki/Preon
https://en.wikipedia.org/wiki/Sterile_neutrino
https://en.wikipedia.org/wiki/Curvaton
https://en.wikipedia.org/wiki/Axion
https://en.wikipedia.org/wiki/Dilaton
https://en.wikipedia.org/wiki/Cold_dark_matter
https://en.wikipedia.org/wiki/Phantom_energy
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