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106-705: INSPIRE-HEP is an open access digital library for the field of high energy physics (HEP). It is the successor of the Stanford Physics Information Retrieval System (SPIRES) database, the main literature database for high energy physics since the 1970s. SPIRES was (in addition to the CERN Document Server (CDS), arXiv and parts of Astrophysics Data System ) one of the main Particle Information Resources. A survey conducted in 2007 found that SPIRES database users wanted

212-487: A Hilbert space , which is also treated in quantum field theory . Following the convention of particle physicists, the term elementary particles is applied to those particles that are, according to current understanding, presumed to be indivisible and not composed of other particles. Ordinary matter is made from first- generation quarks ( up , down ) and leptons ( electron , electron neutrino ). Collectively, quarks and leptons are called fermions , because they have

318-404: A de Broglie wave in the manner of light . That is, under the appropriate conditions, electrons and other matter would show properties of either particles or waves. The corpuscular properties of a particle are demonstrated when it is shown to have a localized position in space along its trajectory at any given moment. The wave-like nature of light is displayed, for example, when a beam of light

424-402: A microsecond . They occur after collisions between particles made of quarks, such as fast-moving protons and neutrons in cosmic rays . Mesons are also produced in cyclotrons or other particle accelerators . Particles have corresponding antiparticles with the same mass but with opposite electric charges . For example, the antiparticle of the electron is the positron . The electron has

530-498: A quantum spin of half-integers (−1/2, 1/2, 3/2, etc.). This causes the fermions to obey the Pauli exclusion principle , where no two particles may occupy the same quantum state . Quarks have fractional elementary electric charge (−1/3 or 2/3) and leptons have whole-numbered electric charge (0 or 1). Quarks also have color charge , which is labeled arbitrarily with no correlation to actual light color as red, green and blue. Because

636-1055: A " Theory of Everything ", or "TOE". There are also other areas of work in theoretical particle physics ranging from particle cosmology to loop quantum gravity . In principle, all physics (and practical applications developed therefrom) can be derived from the study of fundamental particles. In practice, even if "particle physics" is taken to mean only "high-energy atom smashers", many technologies have been developed during these pioneering investigations that later find wide uses in society. Particle accelerators are used to produce medical isotopes for research and treatment (for example, isotopes used in PET imaging ), or used directly in external beam radiotherapy . The development of superconductors has been pushed forward by their use in particle physics. The World Wide Web and touchscreen technology were initially developed at CERN . Additional applications are found in medicine, national security, industry, computing, science, and workforce development, illustrating

742-860: A beta version of INSPIRE-HEP was freely accessible, in April 2012, it fully replaced SPIRES. A new and upgraded INSPIRE platform was officially released in March 2020. INSPIRE-HEP combines the SPIRES-HEP database content with the open source digital library software Invenio and the content of the CERN Document server. In addition to scientific papers, INSPIRE-HEP provides other information such-as citation metrics, plots extracted from papers or internal experiment notes and tools for users to improve metadata like crowdsourcing for author disambiguation. As of August 2012, INSPIRE-HEP contains 1.1 million records. INSPIRE provides not only

848-648: A charged droplet of oil from falling as a result of gravity. This device could measure the electric charge from as few as 1–150 ions with an error margin of less than 0.3%. Comparable experiments had been done earlier by Thomson's team, using clouds of charged water droplets generated by electrolysis, and in 1911 by Abram Ioffe , who independently obtained the same result as Millikan using charged microparticles of metals, then published his results in 1913. However, oil drops were more stable than water drops because of their slower evaporation rate, and thus more suited to precise experimentation over longer periods of time. Around

954-452: A fourth generation of fermions does not exist. Bosons are the mediators or carriers of fundamental interactions, such as electromagnetism , the weak interaction , and the strong interaction . Electromagnetism is mediated by the photon , the quanta of light . The weak interaction is mediated by the W and Z bosons . The strong interaction is mediated by the gluon , which can link quarks together to form composite particles. Due to

1060-410: A fourth state of matter in which the mean free path of the particles is so long that collisions may be ignored. In 1883, not yet well-known German physicist Heinrich Hertz tried to prove that cathode rays are electrically neutral and got what he interpreted as a confident absence of deflection in electrostatic, as opposed to magnetic, field. However, as J. J. Thomson explained in 1897, Hertz placed

1166-494: A friction that slows the electron. This force is caused by a back-reaction of the electron's own field upon itself. Photons mediate electromagnetic interactions between particles in quantum electrodynamics . An isolated electron at a constant velocity cannot emit or absorb a real photon; doing so would violate conservation of energy and momentum . Instead, virtual photons can transfer momentum between two charged particles. This exchange of virtual photons, for example, generates

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1272-426: A literature database for the field of High-Energy Physics, but for other HEP-related services: High energy physics Particle physics or high-energy physics is the study of fundamental particles and forces that constitute matter and radiation . The field also studies combinations of elementary particles up to the scale of protons and neutrons , while the study of combination of protons and neutrons

1378-1038: A long and growing list of beneficial practical applications with contributions from particle physics. Major efforts to look for physics beyond the Standard Model include the Future Circular Collider proposed for CERN and the Particle Physics Project Prioritization Panel (P5) in the US that will update the 2014 P5 study that recommended the Deep Underground Neutrino Experiment , among other experiments. Electron Electrons play an essential role in numerous physical phenomena, such as electricity , magnetism , chemistry , and thermal conductivity ; they also participate in gravitational , electromagnetic , and weak interactions . Since an electron has charge, it has

1484-460: A model of the electron – the Dirac equation , consistent with relativity theory, by applying relativistic and symmetry considerations to the hamiltonian formulation of the quantum mechanics of the electro-magnetic field. In order to resolve some problems within his relativistic equation, Dirac developed in 1930 a model of the vacuum as an infinite sea of particles with negative energy, later dubbed

1590-430: A negative electric charge, the positron has a positive charge. These antiparticles can theoretically form a corresponding form of matter called antimatter . Some particles, such as the photon , are their own antiparticle. These elementary particles are excitations of the quantum fields that also govern their interactions. The dominant theory explaining these fundamental particles and fields, along with their dynamics,

1696-456: A particle with a positive charge, such as the proton, and a repulsive force on a particle with a negative charge. The strength of this force in nonrelativistic approximation is determined by Coulomb's inverse square law . When an electron is in motion, it generates a magnetic field . The Ampère–Maxwell law relates the magnetic field to the mass motion of electrons (the current ) with respect to an observer. This property of induction supplies

1802-549: A single electron. This prohibition against more than one electron occupying the same quantum energy state became known as the Pauli exclusion principle . The physical mechanism to explain the fourth parameter, which had two distinct possible values, was provided by the Dutch physicists Samuel Goudsmit and George Uhlenbeck . In 1925, they suggested that an electron, in addition to the angular momentum of its orbit, possesses an intrinsic angular momentum and magnetic dipole moment . This

1908-482: A solution that determined the location of an electron over time, this wave equation also could be used to predict the probability of finding an electron near a position, especially a position near where the electron was bound in space, for which the electron wave equations did not change in time. This approach led to a second formulation of quantum mechanics (the first by Heisenberg in 1925), and solutions of Schrödinger's equation, like Heisenberg's, provided derivations of

2014-437: A surplus of the charge carrier, and which situation was a deficit. Between 1838 and 1851, British natural philosopher Richard Laming developed the idea that an atom is composed of a core of matter surrounded by subatomic particles that had unit electric charges . Beginning in 1846, German physicist Wilhelm Eduard Weber theorized that electricity was composed of positively and negatively charged fluids, and their interaction

2120-509: A surrounding electric field ; if that electron is moving relative to an observer, the observer will observe it to generate a magnetic field . Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law . Electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by

2226-435: A wide range of exotic particles . All particles and their interactions observed to date can be described almost entirely by the Standard Model. Dynamics of particles are also governed by quantum mechanics ; they exhibit wave–particle duality , displaying particle-like behaviour under certain experimental conditions and wave -like behaviour in others. In more technical terms, they are described by quantum state vectors in

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2332-407: Is a challenging problem of modern theoretical physics. The admission of the hypothesis of a finite radius of the electron is incompatible to the premises of the theory of relativity. On the other hand, a point-like electron (zero radius) generates serious mathematical difficulties due to the self-energy of the electron tending to infinity. Observation of a single electron in a Penning trap suggests

2438-463: Is a combination of the words electr ic and i on . The suffix - on which is now used to designate other subatomic particles, such as a proton or neutron, is in turn derived from electron. While studying electrical conductivity in rarefied gases in 1859, the German physicist Julius Plücker observed the radiation emitted from the cathode caused phosphorescent light to appear on the tube wall near

2544-425: Is a particle physics theory suggesting that systems with higher energy have a smaller number of dimensions. A third major effort in theoretical particle physics is string theory . String theorists attempt to construct a unified description of quantum mechanics and general relativity by building a theory based on small strings, and branes rather than particles. If the theory is successful, it may be considered

2650-488: Is actually smaller than its true value, and the charge decreases with increasing distance from the electron. This polarization was confirmed experimentally in 1997 using the Japanese TRISTAN particle accelerator. Virtual particles cause a comparable shielding effect for the mass of the electron. The interaction with virtual particles also explains the small (about 0.1%) deviation of the intrinsic magnetic moment of

2756-585: Is analogous to the rotation of the Earth on its axis as it orbits the Sun. The intrinsic angular momentum became known as spin , and explained the previously mysterious splitting of spectral lines observed with a high-resolution spectrograph ; this phenomenon is known as fine structure splitting. In his 1924 dissertation Recherches sur la théorie des quanta (Research on Quantum Theory), French physicist Louis de Broglie hypothesized that all matter can be represented as

2862-415: Is approximately 9.109 × 10  kg , or 5.489 × 10   Da . Due to mass–energy equivalence , this corresponds to a rest energy of 0.511 MeV (8.19 × 10  J) . The ratio between the mass of a proton and that of an electron is about 1836. Astronomical measurements show that the proton-to-electron mass ratio has held the same value, as is predicted by the Standard Model, for at least half

2968-584: Is called nuclear physics . The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and bosons (force-carrying particles). There are three generations of fermions, although ordinary matter is made only from the first fermion generation. The first generation consists of up and down quarks which form protons and neutrons , and electrons and electron neutrinos . The three fundamental interactions known to be mediated by bosons are electromagnetism ,

3074-482: Is called the Standard Model . The reconciliation of gravity to the current particle physics theory is not solved; many theories have addressed this problem, such as loop quantum gravity , string theory and supersymmetry theory . Practical particle physics is the study of these particles in radioactive processes and in particle accelerators such as the Large Hadron Collider . Theoretical particle physics

3180-532: Is explained by the Standard Model , which gained widespread acceptance in the mid-1970s after experimental confirmation of the existence of quarks . It describes the strong , weak , and electromagnetic fundamental interactions , using mediating gauge bosons . The species of gauge bosons are eight gluons , W , W and Z bosons , and the photon . The Standard Model also contains 24 fundamental fermions (12 particles and their associated anti-particles), which are

3286-450: Is in existence, the Coulomb force from the ambient electric field surrounding an electron causes a created positron to be attracted to the original electron, while a created electron experiences a repulsion. This causes what is called vacuum polarization . In effect, the vacuum behaves like a medium having a dielectric permittivity more than unity . Thus the effective charge of an electron

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3392-591: Is in model building where model builders develop ideas for what physics may lie beyond the Standard Model (at higher energies or smaller distances). This work is often motivated by the hierarchy problem and is constrained by existing experimental data. It may involve work on supersymmetry , alternatives to the Higgs mechanism , extra spatial dimensions (such as the Randall–Sundrum models ), Preon theory, combinations of these, or other ideas. Vanishing-dimensions theory

3498-556: Is one of humanity's earliest recorded experiences with electricity . In his 1600 treatise De Magnete , the English scientist William Gilbert coined the Neo-Latin term electrica , to refer to those substances with property similar to that of amber which attract small objects after being rubbed. Both electric and electricity are derived from the Latin ēlectrum (also the root of

3604-407: Is passed through parallel slits thereby creating interference patterns. In 1927, George Paget Thomson and Alexander Reid discovered the interference effect was produced when a beam of electrons was passed through thin celluloid foils and later metal films, and by American physicists Clinton Davisson and Lester Germer by the reflection of electrons from a crystal of nickel . Alexander Reid, who

3710-471: Is the study of these particles in the context of cosmology and quantum theory . The two are closely interrelated: the Higgs boson was postulated by theoretical particle physicists and its presence confirmed by practical experiments. The idea that all matter is fundamentally composed of elementary particles dates from at least the 6th century BC. In the 19th century, John Dalton , through his work on stoichiometry , concluded that each element of nature

3816-600: Is used to extract the parameters of the Standard Model with less uncertainty. This work probes the limits of the Standard Model and therefore expands scientific understanding of nature's building blocks. Those efforts are made challenging by the difficulty of calculating high precision quantities in quantum chromodynamics . Some theorists working in this area use the tools of perturbative quantum field theory and effective field theory , referring to themselves as phenomenologists . Others make use of lattice field theory and call themselves lattice theorists . Another major effort

3922-461: The Dirac sea . This led him to predict the existence of a positron, the antimatter counterpart of the electron. This particle was discovered in 1932 by Carl Anderson , who proposed calling standard electrons negatrons and using electron as a generic term to describe both the positively and negatively charged variants. In 1947, Willis Lamb , working in collaboration with graduate student Robert Retherford , found that certain quantum states of

4028-454: The Lamb shift observed in spectral lines . The Compton Wavelength shows that near elementary particles such as the electron, the uncertainty of the energy allows for the creation of virtual particles near the electron. This wavelength explains the "static" of virtual particles around elementary particles at a close distance. An electron generates an electric field that exerts an attractive force on

4134-413: The Standard Model of particle physics. Individual electrons can now be easily confined in ultra small ( L = 20 nm , W = 20 nm ) CMOS transistors operated at cryogenic temperature over a range of −269 °C (4  K ) to about −258 °C (15  K ). The electron wavefunction spreads in a semiconductor lattice and negligibly interacts with the valence band electrons, so it can be treated in

4240-416: The absolute value of this function is squared , it gives the probability that a particle will be observed near a location—a probability density . Electrons are identical particles because they cannot be distinguished from each other by their intrinsic physical properties. In quantum mechanics, this means that a pair of interacting electrons must be able to swap positions without an observable change to

4346-414: The age of the universe . Electrons have an electric charge of −1.602 176 634 × 10 coulombs , which is used as a standard unit of charge for subatomic particles, and is also called the elementary charge . Within the limits of experimental accuracy, the electron charge is identical to the charge of a proton, but with the opposite sign. The electron is commonly symbolized by e , and

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4452-722: The alloy of the same name ), which came from the Greek word for amber, ἤλεκτρον ( ēlektron ). In the early 1700s, French chemist Charles François du Fay found that if a charged gold-leaf is repulsed by glass rubbed with silk, then the same charged gold-leaf is attracted by amber rubbed with wool. From this and other results of similar types of experiments, du Fay concluded that electricity consists of two electrical fluids , vitreous fluid from glass rubbed with silk and resinous fluid from amber rubbed with wool. These two fluids can neutralize each other when combined. American scientist Ebenezer Kinnersley later also independently reached

4558-544: The atomic nuclei are baryons – the neutron is composed of two down quarks and one up quark, and the proton is composed of two up quarks and one down quark. A baryon is composed of three quarks, and a meson is composed of two quarks (one normal, one anti). Baryons and mesons are collectively called hadrons . Quarks inside hadrons are governed by the strong interaction, thus are subjected to quantum chromodynamics (color charges). The bounded quarks must have their color charge to be neutral, or "white" for analogy with mixing

4664-405: The double-slit experiment . The wave-like nature of the electron allows it to pass through two parallel slits simultaneously, rather than just one slit as would be the case for a classical particle. In quantum mechanics, the wave-like property of one particle can be described mathematically as a complex -valued function, the wave function , commonly denoted by the Greek letter psi ( ψ ). When

4770-462: The e / m ratio but did not take the step of interpreting their results as showing a new particle, while J. J. Thomson would subsequently in 1899 give estimates for the electron charge and mass as well: e  ~  6.8 × 10   esu and m  ~  3 × 10  g The name "electron" was adopted for these particles by the scientific community, mainly due to the advocation by G. F. FitzGerald , J. Larmor , and H. A. Lorentz . The term

4876-414: The muon and the tau , which are identical to the electron in charge, spin and interactions , but are more massive. Leptons differ from the other basic constituent of matter, the quarks , by their lack of strong interaction . All members of the lepton group are fermions because they all have half-odd integer spin; the electron has spin ⁠ 1 / 2 ⁠ . The invariant mass of an electron

4982-459: The spectral lines of the hydrogen atom. However, Bohr's model failed to account for the relative intensities of the spectral lines and it was unsuccessful in explaining the spectra of more complex atoms. Chemical bonds between atoms were explained by Gilbert Newton Lewis , who in 1916 proposed that a covalent bond between two atoms is maintained by a pair of electrons shared between them. Later, in 1927, Walter Heitler and Fritz London gave

5088-399: The spinon , the orbiton and the holon (or chargon). The electron can always be theoretically considered as a bound state of the three, with the spinon carrying the spin of the electron, the orbiton carrying the orbital degree of freedom and the chargon carrying the charge, but in certain conditions they can behave as independent quasiparticles . The issue of the radius of the electron

5194-401: The weak interaction , and the strong interaction . Quarks cannot exist on their own but form hadrons . Hadrons that contain an odd number of quarks are called baryons and those that contain an even number are called mesons . Two baryons, the proton and the neutron , make up most of the mass of ordinary matter. Mesons are unstable and the longest-lived last for only a few hundredths of

5300-599: The 1870s, the English chemist and physicist Sir William Crookes developed the first cathode-ray tube to have a high vacuum inside. He then showed in 1874 that the cathode rays can turn a small paddle wheel when placed in their path. Therefore, he concluded that the rays carried momentum. Furthermore, by applying a magnetic field, he was able to deflect the rays, thereby demonstrating that the beam behaved as though it were negatively charged. In 1879, he proposed that these properties could be explained by regarding cathode rays as composed of negatively charged gaseous molecules in

5406-472: The Coulomb force. Energy emission can occur when a moving electron is deflected by a charged particle, such as a proton. The deceleration of the electron results in the emission of Bremsstrahlung radiation. An inelastic collision between a photon (light) and a solitary (free) electron is called Compton scattering . This collision results in a transfer of momentum and energy between the particles, which modifies

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5512-408: The Standard Model during the 1970s, physicists clarified the origin of the particle zoo. The large number of particles was explained as combinations of a (relatively) small number of more fundamental particles and framed in the context of quantum field theories . This reclassification marked the beginning of modern particle physics. The current state of the classification of all elementary particles

5618-571: The aforementioned color confinement, gluons are never observed independently. The Higgs boson gives mass to the W and Z bosons via the Higgs mechanism – the gluon and photon are expected to be massless . All bosons have an integer quantum spin (0 and 1) and can have the same quantum state . Most aforementioned particles have corresponding antiparticles , which compose antimatter . Normal particles have positive lepton or baryon number , and antiparticles have these numbers negative. Most properties of corresponding antiparticles and particles are

5724-420: The atmosphere. The antiparticle of the electron is called the positron ; it is identical to the electron, except that it carries electrical charge of the opposite sign. When an electron collides with a positron , both particles can be annihilated , producing gamma ray photons . The ancient Greeks noticed that amber attracted small objects when rubbed with fur. Along with lightning , this phenomenon

5830-480: The beginning of the twentieth century, it was found that under certain conditions a fast-moving charged particle caused a condensation of supersaturated water vapor along its path. In 1911, Charles Wilson used this principle to devise his cloud chamber so he could photograph the tracks of charged particles, such as fast-moving electrons. By 1914, experiments by physicists Ernest Rutherford , Henry Moseley , James Franck and Gustav Hertz had largely established

5936-402: The cathode; and the region of the phosphorescent light could be moved by application of a magnetic field. In 1869, Plücker's student Johann Wilhelm Hittorf found that a solid body placed in between the cathode and the phosphorescence would cast a shadow upon the phosphorescent region of the tube. Hittorf inferred that there are straight rays emitted from the cathode and that the phosphorescence

6042-549: The charge carriers were much heavier hydrogen or nitrogen atoms. Schuster's estimates would subsequently turn out to be largely correct. In 1892 Hendrik Lorentz suggested that the mass of these particles (electrons) could be a consequence of their electric charge. While studying naturally fluorescing minerals in 1896, the French physicist Henri Becquerel discovered that they emitted radiation without any exposure to an external energy source. These radioactive materials became

6148-588: The concept of an indivisible quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge "electron" in 1891, and J. J. Thomson and his team of British physicists identified it as a particle in 1897 during the cathode-ray tube experiment . Electrons participate in nuclear reactions , such as nucleosynthesis in stars , where they are known as beta particles . Electrons can be created through beta decay of radioactive isotopes and in high-energy collisions, for instance, when cosmic rays enter

6254-584: The constituents of all matter . Finally, the Standard Model also predicted the existence of a type of boson known as the Higgs boson . On 4 July 2012, physicists with the Large Hadron Collider at CERN announced they had found a new particle that behaves similarly to what is expected from the Higgs boson. The Standard Model, as currently formulated, has 61 elementary particles. Those elementary particles can combine to form composite particles, accounting for

6360-430: The deflecting electrodes in a highly-conductive area of the tube, resulting in a strong screening effect close to their surface. The German-born British physicist Arthur Schuster expanded upon Crookes's experiments by placing metal plates parallel to the cathode rays and applying an electric potential between the plates. The field deflected the rays toward the positively charged plate, providing further evidence that

6466-447: The development of nuclear weapons . Throughout the 1950s and 1960s, a bewildering variety of particles was found in collisions of particles from beams of increasingly high energy. It was referred to informally as the " particle zoo ". Important discoveries such as the CP violation by James Cronin and Val Fitch brought new questions to matter-antimatter imbalance . After the formulation of

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6572-427: The effects of quantum mechanics ; in reality, the so-called classical electron radius has little to do with the true fundamental structure of the electron. There are elementary particles that spontaneously decay into less massive particles. An example is the muon , with a mean lifetime of 2.2 × 10  seconds, which decays into an electron, a muon neutrino and an electron antineutrino . The electron, on

6678-450: The electron from the Bohr magneton (the anomalous magnetic moment ). The extraordinarily precise agreement of this predicted difference with the experimentally determined value is viewed as one of the great achievements of quantum electrodynamics . The apparent paradox in classical physics of a point particle electron having intrinsic angular momentum and magnetic moment can be explained by

6784-560: The electron has an intrinsic magnetic moment along its spin axis. It is approximately equal to one Bohr magneton , which is a physical constant that is equal to 9.274 010 0657 (29) × 10  J⋅T . The orientation of the spin with respect to the momentum of the electron defines the property of elementary particles known as helicity . The electron has no known substructure . Nevertheless, in condensed matter physics , spin–charge separation can occur in some materials. In such cases, electrons 'split' into three independent particles,

6890-456: The energy states of an electron in a hydrogen atom that were equivalent to those that had been derived first by Bohr in 1913, and that were known to reproduce the hydrogen spectrum. Once spin and the interaction between multiple electrons were describable, quantum mechanics made it possible to predict the configuration of electrons in atoms with atomic numbers greater than hydrogen. In 1928, building on Wolfgang Pauli's work, Paul Dirac produced

6996-478: The first experimental deviations from the Standard Model, since neutrinos do not have mass in the Standard Model. Modern particle physics research is focused on subatomic particles , including atomic constituents, such as electrons , protons , and neutrons (protons and neutrons are composite particles called baryons , made of quarks ), that are produced by radioactive and scattering processes; such particles are photons , neutrinos , and muons , as well as

7102-448: The first high-energy particle collider was ADONE , which began operations in 1968. This device accelerated electrons and positrons in opposite directions, effectively doubling the energy of their collision when compared to striking a static target with an electron. The Large Electron–Positron Collider (LEP) at CERN , which was operational from 1989 to 2000, achieved collision energies of 209 GeV and made important measurements for

7208-406: The formation of virtual photons in the electric field generated by the electron. These photons can heuristically be thought of as causing the electron to shift about in a jittery fashion (known as zitterbewegung ), which results in a net circular motion with precession . This motion produces both the spin and the magnetic moment of the electron. In atoms, this creation of virtual photons explains

7314-559: The full explanation of the electron-pair formation and chemical bonding in terms of quantum mechanics . In 1919, the American chemist Irving Langmuir elaborated on the Lewis's static model of the atom and suggested that all electrons were distributed in successive "concentric (nearly) spherical shells, all of equal thickness". In turn, he divided the shells into a number of cells each of which contained one pair of electrons. With this model Langmuir

7420-538: The gravitational interaction, but it has not been detected or completely reconciled with current theories. Many other hypothetical particles have been proposed to address the limitations of the Standard Model. Notably, supersymmetric particles aim to solve the hierarchy problem , axions address the strong CP problem , and various other particles are proposed to explain the origins of dark matter and dark energy . The world's major particle physics laboratories are: Theoretical particle physics attempts to develop

7526-424: The hundreds of other species of particles that have been discovered since the 1960s. The Standard Model has been found to agree with almost all the experimental tests conducted to date. However, most particle physicists believe that it is an incomplete description of nature and that a more fundamental theory awaits discovery (See Theory of Everything ). In recent years, measurements of neutrino mass have provided

7632-421: The hydrogen atom, which should have the same energy, were shifted in relation to each other; the difference came to be called the Lamb shift . About the same time, Polykarp Kusch , working with Henry M. Foley , discovered the magnetic moment of the electron is slightly larger than predicted by Dirac's theory. This small difference was later called anomalous magnetic dipole moment of the electron. This difference

7738-433: The interactions between the quarks store energy which can convert to other particles when the quarks are far apart enough, quarks cannot be observed independently. This is called color confinement . There are three known generations of quarks (up and down, strange and charm , top and bottom ) and leptons (electron and its neutrino, muon and its neutrino , tau and its neutrino ), with strong indirect evidence that

7844-489: The magnetic field and the electron velocity. This centripetal force causes the electron to follow a helical trajectory through the field at a radius called the gyroradius . The acceleration from this curving motion induces the electron to radiate energy in the form of synchrotron radiation. The energy emission in turn causes a recoil of the electron, known as the Abraham–Lorentz–Dirac Force , which creates

7950-462: The magnetic field that drives an electric motor . The electromagnetic field of an arbitrary moving charged particle is expressed by the Liénard–Wiechert potentials , which are valid even when the particle's speed is close to that of light ( relativistic ). When an electron is moving through a magnetic field, it is subject to the Lorentz force that acts perpendicularly to the plane defined by

8056-497: The models, theoretical framework, and mathematical tools to understand current experiments and make predictions for future experiments (see also theoretical physics ). There are several major interrelated efforts being made in theoretical particle physics today. One important branch attempts to better understand the Standard Model and its tests. Theorists make quantitative predictions of observables at collider and astronomical experiments, which along with experimental measurements

8162-426: The negatively charged particles produced by radioactive materials, by heated materials and by illuminated materials were universal. Thomson measured m / e for cathode ray "corpuscles", and made good estimates of the charge e , leading to value for the mass m , finding a value 1400 times less massive than the least massive ion known: hydrogen. In the same year Emil Wiechert and Walter Kaufmann also calculated

8268-430: The other hand, is thought to be stable on theoretical grounds: the electron is the least massive particle with non-zero electric charge, so its decay would violate charge conservation . The experimental lower bound for the electron's mean lifetime is 6.6 × 10 years, at a 90% confidence level . As with all particles, electrons can act as waves. This is called the wave–particle duality and can be demonstrated using

8374-483: The photon or gluon, have no antiparticles. Quarks and gluons additionally have color charges, which influences the strong interaction. Quark's color charges are called red, green and blue (though the particle itself have no physical color), and in antiquarks are called antired, antigreen and antiblue. The gluon can have eight color charges , which are the result of quarks' interactions to form composite particles (gauge symmetry SU(3) ). The neutrons and protons in

8480-551: The photon, have symmetric wave functions instead. In the case of antisymmetry, solutions of the wave equation for interacting electrons result in a zero probability that each pair will occupy the same location or state. This is responsible for the Pauli exclusion principle , which precludes any two electrons from occupying the same quantum state. This principle explains many of the properties of electrons. For example, it causes groups of bound electrons to occupy different orbitals in an atom, rather than all overlapping each other in

8586-662: The portal to provide more services than the, at that time, already 30-year-old system could provide. On the second annual Summit of Information Specialists in Particle Physics and Astrophysics in May 2008, the physics laboratories CERN , DESY , SLAC and Fermilab therefore announced that they would work together to create a new Scientific Information System for high energy physics called INSPIRE. It interacts with other HEP service providers like arXiv.org , Particle Data Group , NASA 's Astrophysics Data System . and HEPdata. In April 2010,

8692-456: The positive protons within atomic nuclei and the negative electrons without allows the composition of the two known as atoms . Ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the main cause of chemical bonding . In 1838, British natural philosopher Richard Laming first hypothesized

8798-452: The positron is symbolized by e . The electron has an intrinsic angular momentum or spin of ⁠ ħ / 2 ⁠ . This property is usually stated by referring to the electron as a spin-1/2 particle. For such particles the spin magnitude is ⁠ ħ / 2 ⁠ , while the result of the measurement of a projection of the spin on any axis can only be ± ⁠ ħ / 2 ⁠ . In addition to spin,

8904-426: The primary colors . More exotic hadrons can have other types, arrangement or number of quarks ( tetraquark , pentaquark ). An atom is made from protons, neutrons and electrons. By modifying the particles inside a normal atom, exotic atoms can be formed. A simple example would be the hydrogen-4.1 , which has one of its electrons replaced with a muon. The graviton is a hypothetical particle that can mediate

9010-403: The rays carried negative charge. By measuring the amount of deflection for a given electric and magnetic field , in 1890 Schuster was able to estimate the charge-to-mass ratio of the ray components. However, this produced a value that was more than a thousand times greater than what was expected, so little credence was given to his calculations at the time. This is because it was assumed that

9116-450: The same conclusion. A decade later Benjamin Franklin proposed that electricity was not from different types of electrical fluid, but a single electrical fluid showing an excess (+) or deficit (−). He gave them the modern charge nomenclature of positive and negative respectively. Franklin thought of the charge carrier as being positive, but he did not correctly identify which situation was

9222-423: The same orbit. In a simplified picture, which often tends to give the wrong idea but may serve to illustrate some aspects, every photon spends some time as a combination of a virtual electron plus its antiparticle, the virtual positron, which rapidly annihilate each other shortly thereafter. The combination of the energy variation needed to create these particles, and the time during which they exist, fall under

9328-444: The same, with a few gets reversed; the electron's antiparticle, positron, has an opposite charge. To differentiate between antiparticles and particles, a plus or negative sign is added in superscript . For example, the electron and the positron are denoted e and e . When a particle and an antiparticle interact with each other, they are annihilated and convert to other particles. Some particles, such as

9434-489: The single particle formalism, by replacing its mass with the effective mass tensor . In the Standard Model of particle physics, electrons belong to the group of subatomic particles called leptons , which are believed to be fundamental or elementary particles . Electrons have the lowest mass of any charged lepton (or electrically charged particle of any type) and belong to the first generation of fundamental particles. The second and third generation contain charged leptons,

9540-435: The state of the system. The wave function of fermions, including electrons, is antisymmetric, meaning that it changes sign when two electrons are swapped; that is, ψ ( r 1 , r 2 ) = − ψ ( r 2 , r 1 ) , where the variables r 1 and r 2 correspond to the first and second electrons, respectively. Since the absolute value is not changed by a sign swap, this corresponds to equal probabilities. Bosons , such as

9646-484: The structure of an atom as a dense nucleus of positive charge surrounded by lower-mass electrons. In 1913, Danish physicist Niels Bohr postulated that electrons resided in quantized energy states, with their energies determined by the angular momentum of the electron's orbit about the nucleus. The electrons could move between those states, or orbits, by the emission or absorption of photons of specific frequencies. By means of these quantized orbits, he accurately explained

9752-498: The subject of much interest by scientists, including the New Zealand physicist Ernest Rutherford who discovered they emitted particles. He designated these particles alpha and beta , on the basis of their ability to penetrate matter. In 1900, Becquerel showed that the beta rays emitted by radium could be deflected by an electric field, and that their mass-to-charge ratio was the same as for cathode rays. This evidence strengthened

9858-423: The term electrolion in 1881. Ten years later, he switched to electron to describe these elementary charges, writing in 1894: "... an estimate was made of the actual amount of this most remarkable fundamental unit of electricity, for which I have since ventured to suggest the name electron ". A 1906 proposal to change to electrion failed because Hendrik Lorentz preferred to keep electron . The word electron

9964-516: The threshold of detectability expressed by the Heisenberg uncertainty relation , Δ E  · Δ t  ≥  ħ . In effect, the energy needed to create these virtual particles, Δ E , can be "borrowed" from the vacuum for a period of time, Δ t , so that their product is no more than the reduced Planck constant , ħ ≈ 6.6 × 10  eV·s . Thus, for a virtual electron, Δ t is at most 1.3 × 10  s . While an electron–positron virtual pair

10070-426: The upper limit of the particle's radius to be 10  meters. The upper bound of the electron radius of 10  meters can be derived using the uncertainty relation in energy. There is also a physical constant called the " classical electron radius ", with the much larger value of 2.8179 × 10  m , greater than the radius of the proton. However, the terminology comes from a simplistic calculation that ignores

10176-624: The use of electromagnetic fields. Special telescopes can detect electron plasma in outer space. Electrons are involved in many applications, such as tribology or frictional charging, electrolysis, electrochemistry, battery technologies, electronics , welding , cathode-ray tubes , photoelectricity, photovoltaic solar panels, electron microscopes , radiation therapy , lasers , gaseous ionization detectors , and particle accelerators . Interactions involving electrons with other subatomic particles are of interest in fields such as chemistry and nuclear physics . The Coulomb force interaction between

10282-482: The view that electrons existed as components of atoms. In 1897, the British physicist J. J. Thomson , with his colleagues John S. Townsend and H. A. Wilson , performed experiments indicating that cathode rays really were unique particles, rather than waves, atoms or molecules as was believed earlier. By 1899 he showed that their charge-to-mass ratio, e / m , was independent of cathode material. He further showed that

10388-468: The wavelength of the photon by an amount called the Compton shift . The maximum magnitude of this wavelength shift is h / m e c , which is known as the Compton wavelength . For an electron, it has a value of 2.43 × 10  m . When the wavelength of the light is long (for instance, the wavelength of the visible light is 0.4–0.7 μm) the wavelength shift becomes negligible. Such interaction between

10494-551: Was Thomson's graduate student, performed the first experiments but he died soon after in a motorcycle accident and is rarely mentioned. De Broglie's prediction of a wave nature for electrons led Erwin Schrödinger to postulate a wave equation for electrons moving under the influence of the nucleus in the atom. In 1926, this equation, the Schrödinger equation , successfully described how electron waves propagated. Rather than yielding

10600-416: Was able to qualitatively explain the chemical properties of all elements in the periodic table, which were known to largely repeat themselves according to the periodic law . In 1924, Austrian physicist Wolfgang Pauli observed that the shell-like structure of the atom could be explained by a set of four parameters that defined every quantum energy state, as long as each state was occupied by no more than

10706-734: Was caused by the rays striking the tube walls. Furthermore, he also discovered that these rays are deflected by magnets just like lines of current. In 1876, the German physicist Eugen Goldstein showed that the rays were emitted perpendicular to the cathode surface, which distinguished between the rays that were emitted from the cathode and the incandescent light. Goldstein dubbed the rays cathode rays . Decades of experimental and theoretical research involving cathode rays were important in J. J. Thomson 's eventual discovery of electrons. Goldstein also experimented with double cathodes and hypothesized that one ray may repulse another, although he didn't believe that any particles might be involved. During

10812-678: Was composed of a single, unique type of particle. The word atom , after the Greek word atomos meaning "indivisible", has since then denoted the smallest particle of a chemical element , but physicists later discovered that atoms are not, in fact, the fundamental particles of nature, but are conglomerates of even smaller particles, such as the electron . The early 20th century explorations of nuclear physics and quantum physics led to proofs of nuclear fission in 1939 by Lise Meitner (based on experiments by Otto Hahn ), and nuclear fusion by Hans Bethe in that same year; both discoveries also led to

10918-672: Was governed by the inverse square law . After studying the phenomenon of electrolysis in 1874, Irish physicist George Johnstone Stoney suggested that there existed a "single definite quantity of electricity", the charge of a monovalent ion . He was able to estimate the value of this elementary charge e by means of Faraday's laws of electrolysis . However, Stoney believed these charges were permanently attached to atoms and could not be removed. In 1881, German physicist Hermann von Helmholtz argued that both positive and negative charges were divided into elementary parts, each of which "behaves like atoms of electricity". Stoney initially coined

11024-426: Was later explained by the theory of quantum electrodynamics , developed by Sin-Itiro Tomonaga , Julian Schwinger and Richard Feynman in the late 1940s. With the development of the particle accelerator during the first half of the twentieth century, physicists began to delve deeper into the properties of subatomic particles . The first successful attempt to accelerate electrons using electromagnetic induction

11130-415: Was made in 1942 by Donald Kerst . His initial betatron reached energies of 2.3 MeV, while subsequent betatrons achieved 300 MeV. In 1947, synchrotron radiation was discovered with a 70 MeV electron synchrotron at General Electric . This radiation was caused by the acceleration of electrons through a magnetic field as they moved near the speed of light. With a beam energy of 1.5 GeV,

11236-413: Was originally coined by George Johnstone Stoney in 1891 as a tentative name for the basic unit of electrical charge (which had then yet to be discovered). The electron's charge was more carefully measured by the American physicists Robert Millikan and Harvey Fletcher in their oil-drop experiment of 1909, the results of which were published in 1911. This experiment used an electric field to prevent

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