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Subatomic particle

In physics, a subatomic particle is a particle smaller than an atom.[1] According to the Standard Model of particle physics, a subatomic particle can be either a composite particle, which is composed of other particles (for example, a baryon, like a proton or a neutron, composed of three quarks; or a meson, composed of two quarks), or an elementary particle, which is not composed of other particles (for example, quarks; or electrons, muons, and tau particles, which are called leptons).[2] Particle physics and nuclear physics study these particles and how they interact.[3] Most force carrying particles like photons or gluons are called bosons and, although they have discrete quanta of energy, do not have rest mass or discrete diameters (other than pure energy wavelength) and are unlike the former particles that have rest mass and cannot overlap or combine which are called fermions.

A composite particle proton is made of two up quark and one down quark, which are elementary particles.

Experiments show that light could behave like a stream of particles (called photons) as well as exhibiting wave-like properties. This led to the concept of wave–particle duality to reflect that quantum-scale particles behave both like particles and like waves; they are sometimes called wavicles to reflect this.[4]

Another concept, the uncertainty principle, states that some of their properties taken together, such as their simultaneous position and momentum, cannot be measured exactly.[5] The wave–particle duality has been shown to apply not only to photons but to more massive particles as well.[6]

Interactions of particles in the framework of quantum field theory are understood as creation and annihilation of quanta of corresponding fundamental interactions. This blends particle physics with field theory.

Even among particle physicists, the exact definition of a particle has diverse descriptions. These professional attempts at the definition of a particle include:[7]

Classification edit

By composition edit

Subatomic particles are either "elementary", i.e. not made of multiple other particles, or "composite" and made of more than one elementary particle bound together.

The elementary particles of the Standard Model are:[8]

 
The Standard Model classification of particles

All of these have now been discovered through experiments, with the latest being the top quark (1995), tau neutrino (2000), and Higgs boson (2012).

Various extensions of the Standard Model predict the existence of an elementary graviton particle and many other elementary particles, but none have been discovered as of 2021.

Hadrons edit

The word hadron comes from Greek and was introduced in 1962 by Lev Okun.[9] Nearly all composite particles contain multiple quarks (and/or antiquarks) bound together by gluons (with a few exceptions with no quarks, such as positronium and muonium). Those containing few (≤ 5) quarks (including antiquarks) are called hadrons. Due to a property known as color confinement, quarks are never found singly but always occur in hadrons containing multiple quarks. The hadrons are divided by number of quarks (including antiquarks) into the baryons containing an odd number of quarks (almost always 3), of which the proton and neutron (the two nucleons) are by far the best known; and the mesons containing an even number of quarks (almost always 2, one quark and one antiquark), of which the pions and kaons are the best known.

Except for the proton and neutron, all other hadrons are unstable and decay into other particles in microseconds or less. A proton is made of two up quarks and one down quark, while the neutron is made of two down quarks and one up quark. These commonly bind together into an atomic nucleus, e.g. a helium-4 nucleus is composed of two protons and two neutrons. Most hadrons do not live long enough to bind into nucleus-like composites; those that do (other than the proton and neutron) form exotic nuclei.

 
Overlap between Bosons, Hadrons, and Fermions

By statistics edit

Any subatomic particle, like any particle in the three-dimensional space that obeys the laws of quantum mechanics, can be either a boson (with integer spin) or a fermion (with odd half-integer spin).

In the Standard Model, all the elementary fermions have spin 1/2, and are divided into the quarks which carry color charge and therefore feel the strong interaction, and the leptons which do not. The elementary bosons comprise the gauge bosons (photon, W and Z, gluons) with spin 1, while the Higgs boson is the only elementary particle with spin zero.

The hypothetical graviton is required theoretically to have spin 2, but is not part of the Standard Model. Some extensions such as supersymmetry predict additional elementary particles with spin 3/2, but none have been discovered as of 2021.

Due to the laws for spin of composite particles, the baryons (3 quarks) have spin either 1/2 or 3/2 and are therefore fermions; the mesons (2 quarks) have integer spin of either 0 or 1 and are therefore bosons.

By mass edit

In special relativity, the energy of a particle at rest equals its mass times the speed of light squared, E = mc2. That is, mass can be expressed in terms of energy and vice versa. If a particle has a frame of reference in which it lies at rest, then it has a positive rest mass and is referred to as massive.

All composite particles are massive. Baryons (meaning "heavy") tend to have greater mass than mesons (meaning "intermediate"), which in turn tend to be heavier than leptons (meaning "lightweight"), but the heaviest lepton (the tau particle) is heavier than the two lightest flavours of baryons (nucleons). It is also certain that any particle with an electric charge is massive.

When originally defined in the 1950s, the terms baryons, mesons and leptons referred to masses; however, after the quark model became accepted in the 1970s, it was recognised that baryons are composites of three quarks, mesons are composites of one quark and one antiquark, while leptons are elementary and are defined as the elementary fermions with no color charge.

All massless particles (particles whose invariant mass is zero) are elementary. These include the photon and gluon, although the latter cannot be isolated.

By decay edit

Most subatomic particles are not stable. All leptons, as well as baryons decay by either the strong force or weak force (except for the proton). Protons are not known to decay, although whether they are "truly" stable is unknown, as some very important Grand Unified Theories (GUTs) actually require it. The μ and τ muons, as well as their antiparticles, decay by the weak force. Neutrinos (and antineutrinos) do not decay, but a related phenomenon of neutrino oscillations is thought to exist even in vacuums. The electron and its antiparticle, the positron, are theoretically stable due to charge conservation unless a lighter particle having magnitude of electric charge  e exists (which is unlikely). Its charge is not shown yet.

Other properties edit

All observable subatomic particles have their electric charge an integer multiple of the elementary charge. The Standard Model's quarks have "non-integer" electric charges, namely, multiple of 1/3 e, but quarks (and other combinations with non-integer electric charge) cannot be isolated due to color confinement. For baryons, mesons, and their antiparticles the constituent quarks' charges sum up to an integer multiple of e.

Through the work of Albert Einstein, Satyendra Nath Bose, Louis de Broglie, and many others, current scientific theory holds that all particles also have a wave nature.[10] This has been verified not only for elementary particles but also for compound particles like atoms and even molecules. In fact, according to traditional formulations of non-relativistic quantum mechanics, wave–particle duality applies to all objects, even macroscopic ones; although the wave properties of macroscopic objects cannot be detected due to their small wavelengths.[11]

Interactions between particles have been scrutinized for many centuries, and a few simple laws underpin how particles behave in collisions and interactions. The most fundamental of these are the laws of conservation of energy and conservation of momentum, which let us make calculations of particle interactions on scales of magnitude that range from stars to quarks.[12] These are the prerequisite basics of Newtonian mechanics, a series of statements and equations in Philosophiae Naturalis Principia Mathematica, originally published in 1687.

Dividing an atom edit

The negatively charged electron has a mass of about 1/1836 of that of a hydrogen atom. The remainder of the hydrogen atom's mass comes from the positively charged proton. The atomic number of an element is the number of protons in its nucleus. Neutrons are neutral particles having a mass slightly greater than that of the proton. Different isotopes of the same element contain the same number of protons but differing numbers of neutrons. The mass number of an isotope is the total number of nucleons (neutrons and protons collectively).

Chemistry concerns itself with how electron sharing binds atoms into structures such as crystals and molecules. The subatomic particles considered important in the understanding of chemistry are the electron, the proton, and the neutron. Nuclear physics deals with how protons and neutrons arrange themselves in nuclei. The study of subatomic particles, atoms and molecules, and their structure and interactions, requires quantum mechanics. Analyzing processes that change the numbers and types of particles requires quantum field theory. The study of subatomic particles per se is called particle physics. The term high-energy physics is nearly synonymous to "particle physics" since creation of particles requires high energies: it occurs only as a result of cosmic rays, or in particle accelerators. Particle phenomenology systematizes the knowledge about subatomic particles obtained from these experiments.[13]

History edit

The term "subatomic particle" is largely a retronym of the 1960s, used to distinguish a large number of baryons and mesons (which comprise hadrons) from particles that are now thought to be truly elementary. Before that hadrons were usually classified as "elementary" because their composition was unknown.

A list of important discoveries follows:

Particle Composition Theorized Discovered Comments
electron
e
elementary (lepton) G. Johnstone Stoney (1874)[14] J. J. Thomson (1897)[15] Minimum unit of electrical charge, for which Stoney suggested the name in 1891.[16] First subatomic particle to be identified.[17]
alpha particle
α
composite (atomic nucleus) never Ernest Rutherford (1899)[18] Proven by Rutherford and Thomas Royds in 1907 to be helium nuclei. Rutherford won the Nobel Prize for Chemistry in 1908 for this discovery.[19]
photon
γ
elementary (quantum) Max Planck (1900)[20] Albert Einstein (1905)[21] Necessary to solve the thermodynamic problem of black-body radiation.
proton
p
composite (baryon) William Prout (1815)[22] Ernest Rutherford (1919, named 1920)[23][24] The nucleus of 1
H
.
neutron
n
composite (baryon) Ernest Rutherford (c.1920[25]) James Chadwick (1932) [26] The second nucleon.
antiparticles   Paul Dirac (1928)[27] Carl D. Anderson (
e+
, 1932)
Revised explanation uses CPT symmetry.
pions
π
composite (mesons) Hideki Yukawa (1935) César Lattes, Giuseppe Occhialini, Cecil Powell (1947) Explains the nuclear force between nucleons. The first meson (by modern definition) to be discovered.
muon
μ
elementary (lepton) never Carl D. Anderson (1936)[28] Called a "meson" at first; but today classed as a lepton.
kaons
K
composite (mesons) never G. D. Rochester, C. C. Butler (1947)[29] Discovered in cosmic rays. The first strange particle.
lambda baryons
Λ
composite (baryons) never University of Melbourne (
Λ0
, 1950)[30]
The first hyperon discovered.
neutrino
ν
elementary (lepton) Wolfgang Pauli (1930), named by Enrico Fermi Clyde Cowan, Frederick Reines (
ν
e
, 1956)
Solved the problem of energy spectrum of beta decay.
quarks
(
u
,
d
,
s
)
elementary Murray Gell-Mann, George Zweig (1964) No particular confirmation event for the quark model.
charm quark
c
elementary (quark) Sheldon Glashow, John Iliopoulos, Luciano Maiani (1970) B. Richter, S. C. C. Ting (
J/ψ
, 1974)
bottom quark
b
elementary (quark) Makoto Kobayashi, Toshihide Maskawa (1973) Leon M. Lederman (
ϒ
, 1977)
gluons elementary (quantum) Harald Fritzsch, Murray Gell-Mann (1972)[31] DESY (1979)
weak gauge bosons
W±
,
Z0
elementary (quantum) Glashow, Weinberg, Salam (1968) CERN (1983) Properties verified through the 1990s.
top quark
t
elementary (quark) Makoto Kobayashi, Toshihide Maskawa (1973)[32] Fermilab (1995)[33] Does not hadronize, but is necessary to complete the Standard Model.
Higgs boson elementary (quantum) Peter Higgs (1964)[34][35] CERN (2012)[36] Thought to be confirmed in 2013. More evidence found in 2014.[37]
tetraquark composite ? Zc(3900), 2013, yet to be confirmed as a tetraquark A new class of hadrons.
pentaquark composite ? Yet another class of hadrons. As of 2019 several are thought to exist.
graviton elementary (quantum) Albert Einstein (1916) Interpretation of a gravitational wave as particles is controversial.[38]
magnetic monopole elementary (unclassified) Paul Dirac (1931)[39] undiscovered

See also edit

References edit

  1. ^ . NTD. Archived from the original on 16 February 2014. Retrieved 5 June 2012.
  2. ^ Bolonkin, Alexander (2011). Universe, Human Immortality and Future Human Evaluation. Elsevier. p. 25. ISBN 9780124158016.
  3. ^ Fritzsch, Harald (2005). Elementary Particles. World Scientific. pp. 11–20. ISBN 978-981-256-141-1.
  4. ^ Hunter, Geoffrey; Wadlinger, Robert L. P. (August 23, 1987). Honig, William M.; Kraft, David W.; Panarella, Emilio (eds.). Quantum Uncertainties: Recent and Future Experiments and Interpretations. Springer US. pp. 331–343. doi:10.1007/978-1-4684-5386-7_18 – via Springer Link. The finite-field model of the photon is both a particle and a wave, and hence we refer to it by Eddington's name "wavicle".
  5. ^ Heisenberg, W. (1927), "Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik", Zeitschrift für Physik (in German), 43 (3–4): 172–198, Bibcode:1927ZPhy...43..172H, doi:10.1007/BF01397280, S2CID 122763326.
  6. ^ Arndt, Markus; Nairz, Olaf; Vos-Andreae, Julian; Keller, Claudia; Van Der Zouw, Gerbrand; Zeilinger, Anton (2000). "Wave-particle duality of C60 molecules". Nature. 401 (6754): 680–682. Bibcode:1999Natur.401..680A. doi:10.1038/44348. PMID 18494170. S2CID 4424892.
  7. ^ "What is a Particle?". 12 November 2020.
  8. ^ Cottingham, W.N.; Greenwood, D.A. (2007). An introduction to the standard model of particle physics. Cambridge University Press. p. 1. ISBN 978-0-521-85249-4.
  9. ^ Okun, Lev (1962). "The theory of weak interaction". Proceedings of 1962 International Conference on High-Energy Physics at CERN. International Conference on High-Energy Physics (plenary talk). CERN, Geneva, CH. p. 845. Bibcode:1962hep..conf..845O.
  10. ^ Greiner, Walter (2001). Quantum Mechanics: An Introduction. Springer. p. 29. ISBN 978-3-540-67458-0.
  11. ^ Eisberg, R. & Resnick, R. (1985). Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles (2nd ed.). John Wiley & Sons. pp. 59–60. ISBN 978-0-471-87373-0. For both large and small wavelengths, both matter and radiation have both particle and wave aspects. [...] But the wave aspects of their motion become more difficult to observe as their wavelengths become shorter. [...] For ordinary macroscopic particles the mass is so large that the momentum is always sufficiently large to make the de Broglie wavelength small enough to be beyond the range of experimental detection, and classical mechanics reigns supreme.
  12. ^ Isaac Newton (1687). Newton's Laws of Motion (Philosophiae Naturalis Principia Mathematica)
  13. ^ Taiebyzadeh, Payam (2017). String Theory; A unified theory and inner dimension of elementary particles (BazDahm). Riverside, Iran: Shamloo Publications Center. ISBN 978-600-116-684-6.
  14. ^ Stoney, G. Johnstone (1881). "LII. On the physical units of nature". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 11 (69): 381–390. doi:10.1080/14786448108627031. ISSN 1941-5982.
  15. ^ Thomson, J.J. (1897). "Cathode Rays". The Electrician. 39: 104.
  16. ^ Klemperer, Otto (1959). "Electron physics: The physics of the free electron". Physics Today. 13 (6): 64–66. Bibcode:1960PhT....13R..64K. doi:10.1063/1.3057011.
  17. ^ Alfred, Randy. "April 30, 1897: J.J. Thomson Announces the Electron ... Sort Of". Wired. ISSN 1059-1028. Retrieved 2022-08-22.
  18. ^ Rutherford, E. (1899). "VIII. Uranium radiation and the electrical conduction produced by it". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 47 (284): 109–163. doi:10.1080/14786449908621245. ISSN 1941-5982.
  19. ^ "The Nobel Prize in Chemistry 1908". NobelPrize.org. Retrieved 2022-08-22.
  20. ^ Klein, Martin J. (1961). "Max Planck and the beginnings of the quantum theory". Archive for History of Exact Sciences. 1 (5): 459–479. doi:10.1007/BF00327765. ISSN 0003-9519. S2CID 121189755.
  21. ^ Einstein, A. (1905). "Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt". Annalen der Physik (in German). 322 (6): 132–148. Bibcode:1905AnP...322..132E. doi:10.1002/andp.19053220607.
  22. ^ Lederman, Leon (1993). The God Particle. ISBN 9780385312110.
  23. ^ Rutherford, Sir Ernest (1920). "The Stability of Atoms". Proceedings of the Physical Society of London. 33 (1): 389–394. Bibcode:1920PPSL...33..389R. doi:10.1088/1478-7814/33/1/337. ISSN 1478-7814.
  24. ^ "There was early debate on what to name the proton as seen in the follow commentary articles by Soddy 1920 and Lodge 1920.
  25. ^ Rutherford, E. (1920). "Bakerian Lecture: Nuclear constitution of atoms". Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character. 97 (686): 374–400. Bibcode:1920RSPSA..97..374R. doi:10.1098/rspa.1920.0040. ISSN 0950-1207.
  26. ^ Chadwick, J. (1932). "The existence of a neutron". Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character. 136 (830): 692–708. Bibcode:1932RSPSA.136..692C. doi:10.1098/rspa.1932.0112. ISSN 0950-1207.
  27. ^ Dirac, P. A. M. (1928). "The quantum theory of the electron". Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character. 117 (778): 610–624. Bibcode:1928RSPSA.117..610D. doi:10.1098/rspa.1928.0023. ISSN 0950-1207.
  28. ^ Anderson, Carl D.; Neddermeyer, Seth H. (1936-08-15). "Cloud Chamber Observations of Cosmic Rays at 4300 Meters Elevation and Near Sea-Level". Physical Review. 50 (4): 263–271. Bibcode:1936PhRv...50..263A. doi:10.1103/PhysRev.50.263. ISSN 0031-899X.
  29. ^ ROCHESTER, G. D.; BUTLER, C. C. (1947). "Evidence for the Existence of New Unstable Elementary Particles". Nature. 160 (4077): 855–857. Bibcode:1947Natur.160..855R. doi:10.1038/160855a0. ISSN 0028-0836. PMID 18917296. S2CID 33881752.
  30. ^ Some sources such as "The Strange Quark". indicate 1947.
  31. ^ Fritzsch, Harald; Gell-Mann, Murray (1972). "Current algebra: Quarks and what else?". EConf. C720906V2: 135–165. arXiv:hep-ph/0208010.
  32. ^ Kobayashi, Makoto; Maskawa, Toshihide (1973). "C P -Violation in the Renormalizable Theory of Weak Interaction". Progress of Theoretical Physics. 49 (2): 652–657. Bibcode:1973PThPh..49..652K. doi:10.1143/PTP.49.652. hdl:2433/66179. ISSN 0033-068X. S2CID 14006603.
  33. ^ Abachi, S.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adam, I.; Adams, D. L.; Adams, M.; Ahn, S.; Aihara, H.; Alitti, J.; Álvarez, G.; Alves, G. A.; Amidi, E.; Amos, N.; Anderson, E. W. (1995-04-03). "Observation of the Top Quark". Physical Review Letters. 74 (14): 2632–2637. arXiv:hep-ex/9503003. Bibcode:1995PhRvL..74.2632A. doi:10.1103/PhysRevLett.74.2632. hdl:1969.1/181526. ISSN 0031-9007. PMID 10057979. S2CID 42826202.
  34. ^ "Letters from the Past - A PRL Retrospective". Physical Review Letters. 2014-02-12. Retrieved 2022-08-22.
  35. ^ Higgs, Peter W. (1964-10-19). "Broken Symmetries and the Masses of Gauge Bosons". Physical Review Letters. 13 (16): 508–509. Bibcode:1964PhRvL..13..508H. doi:10.1103/PhysRevLett.13.508. ISSN 0031-9007.
  36. ^ Aad, G.; Abajyan, T.; Abbott, B.; Abdallah, J.; Abdel Khalek, S.; Abdelalim, A.A.; Abdinov, O.; Aben, R.; Abi, B.; Abolins, M.; AbouZeid, O.S.; Abramowicz, H.; Abreu, H.; Acharya, B.S.; Adamczyk, L. (2012). "Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC". Physics Letters B. 716 (1): 1–29. arXiv:1207.7214. Bibcode:2012PhLB..716....1A. doi:10.1016/j.physletb.2012.08.020. S2CID 119169617.
  37. ^ "CERN experiments report new Higgs boson measurements". cern.ch. 23 June 2014.
  38. ^ Moskowitz, Clara. "Multiverse Controversy Heats Up over Gravitational Waves". Scientific American. Retrieved 2022-08-22.
  39. ^ Dirac, P. A. M. (1931). "Quantised singularities in the electromagnetic field". Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character. 133 (821): 60–72. Bibcode:1931RSPSA.133...60D. doi:10.1098/rspa.1931.0130. ISSN 0950-1207.

Further reading edit

General readers edit

Textbooks edit

  • Coughlan, G.D., J.E. Dodd, and B.M. Gripaios (2006). The Ideas of Particle Physics: An Introduction for Scientists, 3rd ed. Cambridge Univ. Press. An undergraduate text for those not majoring in physics.
  • Griffiths, David J. (1987). Introduction to Elementary Particles. John Wiley & Sons. ISBN 978-0-471-60386-3.
  • Kane, Gordon L. (1987). Modern Elementary Particle Physics. Perseus Books. ISBN 978-0-201-11749-3.

External links edit

  • University of California: Particle Data Group.

subatomic, particle, physics, subatomic, particle, particle, smaller, than, atom, according, standard, model, particle, physics, subatomic, particle, either, composite, particle, which, composed, other, particles, example, baryon, like, proton, neutron, compos. In physics a subatomic particle is a particle smaller than an atom 1 According to the Standard Model of particle physics a subatomic particle can be either a composite particle which is composed of other particles for example a baryon like a proton or a neutron composed of three quarks or a meson composed of two quarks or an elementary particle which is not composed of other particles for example quarks or electrons muons and tau particles which are called leptons 2 Particle physics and nuclear physics study these particles and how they interact 3 Most force carrying particles like photons or gluons are called bosons and although they have discrete quanta of energy do not have rest mass or discrete diameters other than pure energy wavelength and are unlike the former particles that have rest mass and cannot overlap or combine which are called fermions A composite particle proton is made of two up quark and one down quark which are elementary particles Experiments show that light could behave like a stream of particles called photons as well as exhibiting wave like properties This led to the concept of wave particle duality to reflect that quantum scale particles behave both like particles and like waves they are sometimes called wavicles to reflect this 4 Another concept the uncertainty principle states that some of their properties taken together such as their simultaneous position and momentum cannot be measured exactly 5 The wave particle duality has been shown to apply not only to photons but to more massive particles as well 6 Interactions of particles in the framework of quantum field theory are understood as creation and annihilation of quanta of corresponding fundamental interactions This blends particle physics with field theory Even among particle physicists the exact definition of a particle has diverse descriptions These professional attempts at the definition of a particle include 7 A particle is a collapsed wave function A particle is a quantum excitation of a field A particle is an irreducible representation of the Poincare group A particle is an observed thingContents 1 Classification 1 1 By composition 1 1 1 Hadrons 1 2 By statistics 1 3 By mass 1 4 By decay 2 Other properties 3 Dividing an atom 4 History 5 See also 6 References 7 Further reading 7 1 General readers 7 2 Textbooks 8 External linksClassification editBy composition edit Subatomic particles are either elementary i e not made of multiple other particles or composite and made of more than one elementary particle bound together The elementary particles of the Standard Model are 8 Six flavors of quarks up down strange charm bottom and top Six types of leptons electron electron neutrino muon muon neutrino tau tau neutrino Twelve gauge bosons force carriers the photon of electromagnetism the three W and Z bosons of the weak force and the eight gluons of the strong force The Higgs boson nbsp The Standard Model classification of particlesAll of these have now been discovered through experiments with the latest being the top quark 1995 tau neutrino 2000 and Higgs boson 2012 Various extensions of the Standard Model predict the existence of an elementary graviton particle and many other elementary particles but none have been discovered as of 2021 Hadrons edit The word hadron comes from Greek and was introduced in 1962 by Lev Okun 9 Nearly all composite particles contain multiple quarks and or antiquarks bound together by gluons with a few exceptions with no quarks such as positronium and muonium Those containing few 5 quarks including antiquarks are called hadrons Due to a property known as color confinement quarks are never found singly but always occur in hadrons containing multiple quarks The hadrons are divided by number of quarks including antiquarks into the baryons containing an odd number of quarks almost always 3 of which the proton and neutron the two nucleons are by far the best known and the mesons containing an even number of quarks almost always 2 one quark and one antiquark of which the pions and kaons are the best known Except for the proton and neutron all other hadrons are unstable and decay into other particles in microseconds or less A proton is made of two up quarks and one down quark while the neutron is made of two down quarks and one up quark These commonly bind together into an atomic nucleus e g a helium 4 nucleus is composed of two protons and two neutrons Most hadrons do not live long enough to bind into nucleus like composites those that do other than the proton and neutron form exotic nuclei nbsp Overlap between Bosons Hadrons and FermionsBy statistics edit Main article Spin statistics theorem Any subatomic particle like any particle in the three dimensional space that obeys the laws of quantum mechanics can be either a boson with integer spin or a fermion with odd half integer spin In the Standard Model all the elementary fermions have spin 1 2 and are divided into the quarks which carry color charge and therefore feel the strong interaction and the leptons which do not The elementary bosons comprise the gauge bosons photon W and Z gluons with spin 1 while the Higgs boson is the only elementary particle with spin zero The hypothetical graviton is required theoretically to have spin 2 but is not part of the Standard Model Some extensions such as supersymmetry predict additional elementary particles with spin 3 2 but none have been discovered as of 2021 Due to the laws for spin of composite particles the baryons 3 quarks have spin either 1 2 or 3 2 and are therefore fermions the mesons 2 quarks have integer spin of either 0 or 1 and are therefore bosons By mass edit In special relativity the energy of a particle at rest equals its mass times the speed of light squared E mc2 That is mass can be expressed in terms of energy and vice versa If a particle has a frame of reference in which it lies at rest then it has a positive rest mass and is referred to as massive All composite particles are massive Baryons meaning heavy tend to have greater mass than mesons meaning intermediate which in turn tend to be heavier than leptons meaning lightweight but the heaviest lepton the tau particle is heavier than the two lightest flavours of baryons nucleons It is also certain that any particle with an electric charge is massive When originally defined in the 1950s the terms baryons mesons and leptons referred to masses however after the quark model became accepted in the 1970s it was recognised that baryons are composites of three quarks mesons are composites of one quark and one antiquark while leptons are elementary and are defined as the elementary fermions with no color charge All massless particles particles whose invariant mass is zero are elementary These include the photon and gluon although the latter cannot be isolated By decay edit Most subatomic particles are not stable All leptons as well as baryons decay by either the strong force or weak force except for the proton Protons are not known to decay although whether they are truly stable is unknown as some very important Grand Unified Theories GUTs actually require it The m and t muons as well as their antiparticles decay by the weak force Neutrinos and antineutrinos do not decay but a related phenomenon of neutrino oscillations is thought to exist even in vacuums The electron and its antiparticle the positron are theoretically stable due to charge conservation unless a lighter particle having magnitude of electric charge e exists which is unlikely Its charge is not shown yet Other properties editAll observable subatomic particles have their electric charge an integer multiple of the elementary charge The Standard Model s quarks have non integer electric charges namely multiple of 1 3 e but quarks and other combinations with non integer electric charge cannot be isolated due to color confinement For baryons mesons and their antiparticles the constituent quarks charges sum up to an integer multiple of e Through the work of Albert Einstein Satyendra Nath Bose Louis de Broglie and many others current scientific theory holds that all particles also have a wave nature 10 This has been verified not only for elementary particles but also for compound particles like atoms and even molecules In fact according to traditional formulations of non relativistic quantum mechanics wave particle duality applies to all objects even macroscopic ones although the wave properties of macroscopic objects cannot be detected due to their small wavelengths 11 Interactions between particles have been scrutinized for many centuries and a few simple laws underpin how particles behave in collisions and interactions The most fundamental of these are the laws of conservation of energy and conservation of momentum which let us make calculations of particle interactions on scales of magnitude that range from stars to quarks 12 These are the prerequisite basics of Newtonian mechanics a series of statements and equations in Philosophiae Naturalis Principia Mathematica originally published in 1687 Dividing an atom editThe negatively charged electron has a mass of about 1 1836 of that of a hydrogen atom The remainder of the hydrogen atom s mass comes from the positively charged proton The atomic number of an element is the number of protons in its nucleus Neutrons are neutral particles having a mass slightly greater than that of the proton Different isotopes of the same element contain the same number of protons but differing numbers of neutrons The mass number of an isotope is the total number of nucleons neutrons and protons collectively Chemistry concerns itself with how electron sharing binds atoms into structures such as crystals and molecules The subatomic particles considered important in the understanding of chemistry are the electron the proton and the neutron Nuclear physics deals with how protons and neutrons arrange themselves in nuclei The study of subatomic particles atoms and molecules and their structure and interactions requires quantum mechanics Analyzing processes that change the numbers and types of particles requires quantum field theory The study of subatomic particles per se is called particle physics The term high energy physics is nearly synonymous to particle physics since creation of particles requires high energies it occurs only as a result of cosmic rays or in particle accelerators Particle phenomenology systematizes the knowledge about subatomic particles obtained from these experiments 13 History editMain articles History of subatomic physics and Timeline of particle discoveries The term subatomic particle is largely a retronym of the 1960s used to distinguish a large number of baryons and mesons which comprise hadrons from particles that are now thought to be truly elementary Before that hadrons were usually classified as elementary because their composition was unknown A list of important discoveries follows Particle Composition Theorized Discovered Commentselectron e elementary lepton G Johnstone Stoney 1874 14 J J Thomson 1897 15 Minimum unit of electrical charge for which Stoney suggested the name in 1891 16 First subatomic particle to be identified 17 alpha particle a composite atomic nucleus never Ernest Rutherford 1899 18 Proven by Rutherford and Thomas Royds in 1907 to be helium nuclei Rutherford won the Nobel Prize for Chemistry in 1908 for this discovery 19 photon g elementary quantum Max Planck 1900 20 Albert Einstein 1905 21 Necessary to solve the thermodynamic problem of black body radiation proton p composite baryon William Prout 1815 22 Ernest Rutherford 1919 named 1920 23 24 The nucleus of 1 H neutron n composite baryon Ernest Rutherford c 1920 25 James Chadwick 1932 26 The second nucleon antiparticles Paul Dirac 1928 27 Carl D Anderson e 1932 Revised explanation uses CPT symmetry pions p composite mesons Hideki Yukawa 1935 Cesar Lattes Giuseppe Occhialini Cecil Powell 1947 Explains the nuclear force between nucleons The first meson by modern definition to be discovered muon m elementary lepton never Carl D Anderson 1936 28 Called a meson at first but today classed as a lepton kaons K composite mesons never G D Rochester C C Butler 1947 29 Discovered in cosmic rays The first strange particle lambda baryons L composite baryons never University of Melbourne L0 1950 30 The first hyperon discovered neutrino n elementary lepton Wolfgang Pauli 1930 named by Enrico Fermi Clyde Cowan Frederick Reines ne 1956 Solved the problem of energy spectrum of beta decay quarks u d s elementary Murray Gell Mann George Zweig 1964 No particular confirmation event for the quark model charm quark c elementary quark Sheldon Glashow John Iliopoulos Luciano Maiani 1970 B Richter S C C Ting J ps 1974 bottom quark b elementary quark Makoto Kobayashi Toshihide Maskawa 1973 Leon M Lederman ϒ 1977 gluons elementary quantum Harald Fritzsch Murray Gell Mann 1972 31 DESY 1979 weak gauge bosons W Z0 elementary quantum Glashow Weinberg Salam 1968 CERN 1983 Properties verified through the 1990s top quark t elementary quark Makoto Kobayashi Toshihide Maskawa 1973 32 Fermilab 1995 33 Does not hadronize but is necessary to complete the Standard Model Higgs boson elementary quantum Peter Higgs 1964 34 35 CERN 2012 36 Thought to be confirmed in 2013 More evidence found in 2014 37 tetraquark composite Zc 3900 2013 yet to be confirmed as a tetraquark A new class of hadrons pentaquark composite Yet another class of hadrons As of 2019 update several are thought to exist graviton elementary quantum Albert Einstein 1916 Interpretation of a gravitational wave as particles is controversial 38 magnetic monopole elementary unclassified Paul Dirac 1931 39 undiscoveredSee also edit nbsp Physics portalAtom Journey Across the Subatomic Cosmos book Atom An Odyssey from the Big Bang to Life on Earth and Beyond book CPT invariance Dark matter Hot spot effect in subatomic physics List of fictional elements materials isotopes and atomic particles List of particles Poincare symmetryReferences edit Subatomic particles NTD Archived from the original on 16 February 2014 Retrieved 5 June 2012 Bolonkin Alexander 2011 Universe Human Immortality and Future Human Evaluation Elsevier p 25 ISBN 9780124158016 Fritzsch Harald 2005 Elementary Particles World Scientific pp 11 20 ISBN 978 981 256 141 1 Hunter Geoffrey Wadlinger Robert L P August 23 1987 Honig William M Kraft David W Panarella Emilio eds Quantum Uncertainties Recent and Future Experiments and Interpretations Springer US pp 331 343 doi 10 1007 978 1 4684 5386 7 18 via Springer Link The finite field model of the photon is both a particle and a wave and hence we refer to it by Eddington s name wavicle Heisenberg W 1927 Uber den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik Zeitschrift fur Physik in German 43 3 4 172 198 Bibcode 1927ZPhy 43 172H doi 10 1007 BF01397280 S2CID 122763326 Arndt Markus Nairz Olaf Vos Andreae Julian Keller Claudia Van Der Zouw Gerbrand Zeilinger Anton 2000 Wave particle duality of C60 molecules Nature 401 6754 680 682 Bibcode 1999Natur 401 680A doi 10 1038 44348 PMID 18494170 S2CID 4424892 What is a Particle 12 November 2020 Cottingham W N Greenwood D A 2007 An introduction to the standard model of particle physics Cambridge University Press p 1 ISBN 978 0 521 85249 4 Okun Lev 1962 The theory of weak interaction Proceedings of 1962 International Conference on High Energy Physics at CERN International Conference on High Energy Physics plenary talk CERN Geneva CH p 845 Bibcode 1962hep conf 845O Greiner Walter 2001 Quantum Mechanics An Introduction Springer p 29 ISBN 978 3 540 67458 0 Eisberg R amp Resnick R 1985 Quantum Physics of Atoms Molecules Solids Nuclei and Particles 2nd ed John Wiley amp Sons pp 59 60 ISBN 978 0 471 87373 0 For both large and small wavelengths both matter and radiation have both particle and wave aspects But the wave aspects of their motion become more difficult to observe as their wavelengths become shorter For ordinary macroscopic particles the mass is so large that the momentum is always sufficiently large to make the de Broglie wavelength small enough to be beyond the range of experimental detection and classical mechanics reigns supreme Isaac Newton 1687 Newton s Laws of Motion Philosophiae Naturalis Principia Mathematica Taiebyzadeh Payam 2017 String Theory A unified theory and inner dimension of elementary particles BazDahm Riverside Iran Shamloo Publications Center ISBN 978 600 116 684 6 Stoney G Johnstone 1881 LII On the physical units of nature The London Edinburgh and Dublin Philosophical Magazine and Journal of Science 11 69 381 390 doi 10 1080 14786448108627031 ISSN 1941 5982 Thomson J J 1897 Cathode Rays The Electrician 39 104 Klemperer Otto 1959 Electron physics The physics of the free electron Physics Today 13 6 64 66 Bibcode 1960PhT 13R 64K doi 10 1063 1 3057011 Alfred Randy April 30 1897 J J Thomson Announces the Electron Sort Of Wired ISSN 1059 1028 Retrieved 2022 08 22 Rutherford E 1899 VIII Uranium radiation and the electrical conduction produced by it The London Edinburgh and Dublin Philosophical Magazine and Journal of Science 47 284 109 163 doi 10 1080 14786449908621245 ISSN 1941 5982 The Nobel Prize in Chemistry 1908 NobelPrize org Retrieved 2022 08 22 Klein Martin J 1961 Max Planck and the beginnings of the quantum theory Archive for History of Exact Sciences 1 5 459 479 doi 10 1007 BF00327765 ISSN 0003 9519 S2CID 121189755 Einstein A 1905 Uber einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt Annalen der Physik in German 322 6 132 148 Bibcode 1905AnP 322 132E doi 10 1002 andp 19053220607 Lederman Leon 1993 The God Particle ISBN 9780385312110 Rutherford Sir Ernest 1920 The Stability of Atoms Proceedings of the Physical Society of London 33 1 389 394 Bibcode 1920PPSL 33 389R doi 10 1088 1478 7814 33 1 337 ISSN 1478 7814 There was early debate on what to name the proton as seen in the follow commentary articles by Soddy 1920 and Lodge 1920 Rutherford E 1920 Bakerian Lecture Nuclear constitution of atoms Proceedings of the Royal Society of London Series A Containing Papers of a Mathematical and Physical Character 97 686 374 400 Bibcode 1920RSPSA 97 374R doi 10 1098 rspa 1920 0040 ISSN 0950 1207 Chadwick J 1932 The existence of a neutron Proceedings of the Royal Society of London Series A Containing Papers of a Mathematical and Physical Character 136 830 692 708 Bibcode 1932RSPSA 136 692C doi 10 1098 rspa 1932 0112 ISSN 0950 1207 Dirac P A M 1928 The quantum theory of the electron Proceedings of the Royal Society of London Series A Containing Papers of a Mathematical and Physical Character 117 778 610 624 Bibcode 1928RSPSA 117 610D doi 10 1098 rspa 1928 0023 ISSN 0950 1207 Anderson Carl D Neddermeyer Seth H 1936 08 15 Cloud Chamber Observations of Cosmic Rays at 4300 Meters Elevation and Near Sea Level Physical Review 50 4 263 271 Bibcode 1936PhRv 50 263A doi 10 1103 PhysRev 50 263 ISSN 0031 899X ROCHESTER G D BUTLER C C 1947 Evidence for the Existence of New Unstable Elementary Particles Nature 160 4077 855 857 Bibcode 1947Natur 160 855R doi 10 1038 160855a0 ISSN 0028 0836 PMID 18917296 S2CID 33881752 Some sources such as The Strange Quark indicate 1947 Fritzsch Harald Gell Mann Murray 1972 Current algebra Quarks and what else EConf C720906V2 135 165 arXiv hep ph 0208010 Kobayashi Makoto Maskawa Toshihide 1973 C P Violation in the Renormalizable Theory of Weak Interaction Progress of Theoretical Physics 49 2 652 657 Bibcode 1973PThPh 49 652K doi 10 1143 PTP 49 652 hdl 2433 66179 ISSN 0033 068X S2CID 14006603 Abachi S Abbott B Abolins M Acharya B S Adam I Adams D L Adams M Ahn S Aihara H Alitti J Alvarez G Alves G A Amidi E Amos N Anderson E W 1995 04 03 Observation of the Top Quark Physical Review Letters 74 14 2632 2637 arXiv hep ex 9503003 Bibcode 1995PhRvL 74 2632A doi 10 1103 PhysRevLett 74 2632 hdl 1969 1 181526 ISSN 0031 9007 PMID 10057979 S2CID 42826202 Letters from the Past A PRL Retrospective Physical Review Letters 2014 02 12 Retrieved 2022 08 22 Higgs Peter W 1964 10 19 Broken Symmetries and the Masses of Gauge Bosons Physical Review Letters 13 16 508 509 Bibcode 1964PhRvL 13 508H doi 10 1103 PhysRevLett 13 508 ISSN 0031 9007 Aad G Abajyan T Abbott B Abdallah J Abdel Khalek S Abdelalim A A Abdinov O Aben R Abi B Abolins M AbouZeid O S Abramowicz H Abreu H Acharya B S Adamczyk L 2012 Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC Physics Letters B 716 1 1 29 arXiv 1207 7214 Bibcode 2012PhLB 716 1A doi 10 1016 j physletb 2012 08 020 S2CID 119169617 CERN experiments report new Higgs boson measurements cern ch 23 June 2014 Moskowitz Clara Multiverse Controversy Heats Up over Gravitational Waves Scientific American Retrieved 2022 08 22 Dirac P A M 1931 Quantised singularities in the electromagnetic field Proceedings of the Royal Society of London Series A Containing Papers of a Mathematical and Physical Character 133 821 60 72 Bibcode 1931RSPSA 133 60D doi 10 1098 rspa 1931 0130 ISSN 0950 1207 Further reading editGeneral readers edit Feynman R P amp Weinberg S 1987 Elementary Particles and the Laws of Physics The 1986 Dirac Memorial Lectures Cambridge Univ Press Greene Brian 1999 The Elegant Universe W W Norton amp Company ISBN 978 0 393 05858 1 Oerter Robert 2006 The Theory of Almost Everything The Standard Model the Unsung Triumph of Modern Physics Plume ISBN 978 0452287860 Schumm Bruce A 2004 Deep Down Things The Breathtaking Beauty of Particle Physics Johns Hopkins University Press ISBN 0 8018 7971 X Veltman Martinus 2003 Facts and Mysteries in Elementary Particle Physics World Scientific ISBN 978 981 238 149 1 Textbooks edit Coughlan G D J E Dodd and B M Gripaios 2006 The Ideas of Particle Physics An Introduction for Scientists 3rd ed Cambridge Univ Press An undergraduate text for those not majoring in physics Griffiths David J 1987 Introduction to Elementary Particles John Wiley amp Sons ISBN 978 0 471 60386 3 Kane Gordon L 1987 Modern Elementary Particle Physics Perseus Books ISBN 978 0 201 11749 3 External links edit nbsp Wikimedia Commons has media related to Subatomic particles University of California Particle Data Group Retrieved from https en wikipedia org w index php title Subatomic particle amp oldid 1183795492, wikipedia, wiki, book, books, library,

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