Radiation
Editor-In-Chief: Henry A. Hoff
Radiation is an action or process of throwing or sending out a traveling ray in a line, beam, or stream of small relative cross section.
At right is an image of an impact crater on the surface of Venus. It is a likely example of meteor radiation damage.
Rays
Def. a beam of light or radiation is called a ray.
Def. an action or process of throwing or sending out a traveling ray in a line, beam, or stream of small cross section is called radiation.
The term radiation is often used to refer to the ray itself.
Def. the shooting forth of anything from a point or surface, like the diverging rays of light; as, the radiation of heat is called radiation.
Rays may have a temporal, spectral, or spatial distribution.
They may also be dependent on other variables as yet unknown.
A delta ray is characterized by very fast electrons produced in quantity by alpha particles or other fast energetic charged particles knocking orbiting electrons out of atoms. Collectively, these electrons are defined as delta radiation when they have sufficient energy to ionize further atoms through subsequent interactions on their own.
Epsilon radiation is tertiary radiation caused by secondary radiation (e.g., delta radiation). Epsilon rays are a form of particle radiation and are composed of electrons. The term is very rarely used today.
Radiation theory
Def. a theory of the science of the biological, chemical, physical, and logical laws (or principles) with respect to any radiation is called a theory of radiation.
Particle radiation consists of a stream of charged or neutral particles, from the size of subatomic elementary particles upwards of rocky and gaseous objects to even larger more loosely bound entities.
Strong forces
A "new type of neutron star model (Q stars) [is such that] high-density, electrically neutral baryonic matter is a coherent classical solution to an effective field theory of strong forces and is bound in the absence of gravity. [...] allows massive compact objects, [...] and has no macroscopic minimum mass."[1]
"Compact objects in astronomy are usually analyzed in terms of theoretical characteristics of neutron stars or black holes that are based upon calculations of equations of state for matter at very high densities. At such high densities, the effects of strong forces cannot be neglected. There are several conventional approaches to describing nuclear forces, all of which find that for a baryon number greater than ~250, a nucleus will become energetically unbound. High-density hadronic matter is not stable in these theories until there are enough baryons for gravitational binding to form a neutron star, typically with a minimum mass ≳ 0.1 M⊙ and maximum mass ≲ 3 M⊙."[1]
"Another possibility [called "baryon matter"] is that in the absence of gravity high-density baryonic matter is bound by purely strong forces. [...] nongravitationally bound bulk hadronic matter is consistent with nuclear physics data [...] and low-energy strong interaction data [...] The effective field theory approach has many successes in nuclear physics [...] suggesting that bulk hadronic matter is just as likely to be a correct description of matter at high densities as conventional, unbound hadronic matter."[1]
"The idea behind baryon matter is that a macroscopic state may exist in which a smaller effective baryon mass inside some region makes the state energetically favored over free particles. [...] This state will appear in the limit of large baryon number as an electrically neutral coherent bound state of neutrons, protons, and electrons in β-decay equilibrium."[1]
Meteors
Particle radiation upwards in size above that of atomic nuclei may be lumped together as meteor radiation.
Galaxy clusters
"Galaxies and clusters of galaxies are not uniformly distributed in the Universe, instead they collect into vast clusters and sheets and walls of galaxies interspersed with large voids in which very few galaxies seem to exist. The map above shows many of these superclusters including the Virgo supercluster - the minor supercluster of which our galaxy is just a minor member. The entire map is approximately 7 percent of the diameter of the entire visible Universe."[2]
High-velocity galaxies
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"The irregular galaxy NGC 1427A is a spectacular example of the resulting stellar rumble. Under the gravitational grasp of a large gang of galaxies, called the Fornax cluster, the small bluish galaxy is plunging headlong into the group at 600 kilometers per second or nearly 400 miles per second."[3]
"Galaxy clusters, like the Fornax cluster, contain hundreds or even thousands of individual galaxies. Within the Fornax cluster, there is a considerable amount of gas lying between the galaxies. When the gas within NGC 1427A collides with the Fornax gas, it is compressed to the point that it starts to collapse under its own gravity. This leads to formation of the myriad of new stars seen across NGC 1427A, which give the galaxy an overall arrowhead shape that appears to point in the direction of the galaxy's high-velocity motion."[3]
Hypervelocity stars
"To date, all of the reported hypervelocity stars (HVSs), which are believed to be ejected from the Galactic center, are blue and therefore almost certainly young.”[4]
Def. a high-velocity star moving through space with an abnormally high velocity relative to the surrounding interstellar medium is called a runaway star.
Clouds
Def. a visible mass of
- water droplets suspended in the air ...
- dust,
- steam ...
- smoke ...
- a group or swarm is called a cloud.
Clouds have been observed on other planets and moons within the Solar System, but, due to their different temperature characteristics, they are composed of other substances such as methane, ammonia, and sulfuric acid.
Aerometeors
Def. a discrete unit of air, wind, or mist traveling or falling through or partially through an atmosphere is called an aerometeor.
Def. any of the high-speed, high-altitude air currents that circle the Earth in a westerly direction is called a jet stream.
Plasma meteors
A coronal cloud is a cloud, or cloud-like, natural astronomical entity, composed of plasma and usually associated with a star or other astronomical object where the temperature is such that X-rays are emitted. While small coronal clouds are above the photosphere of many different visual spectral type stars, others occupy parts of the interstellar medium (ISM), extending sometimes millions of kilometers into space, or thousands of light-years, depending on the size of the associated object such as a galaxy.
At left is a radiated object and its associated phenomena.
Ultra-violet studies of Mira by NASA's Galaxy Evolution Explorer (Galex) space telescope have revealed that it sheds a trail of material from the outer envelope, leaving a tail 13 light-years in length, formed over tens of thousands of years.[5][6] It is thought that a hot bow-wave of compressed plasma/gas is the cause of the tail; the bow-wave is a result of the interaction of the stellar wind from Mira A with gas in interstellar space, through which Mira is moving at an extremely high speed of 130 kilometres/second (291,000 miles per hour).[7][8] The tail consists of material stripped from the head of the bow-wave, which is also visible in ultra-violet observations. Mira's bow-shock will eventually evolve into a planetary nebula, the form of which will be considerably affected by the motion through the interstellar medium (ISM).[9]
Gaseous meteors
Gaseous objects have at least one chemical element or compound present in the gaseous state. These gaseous components make up at least 50 % of the detectable portion of the gaseous object. Atmospheric astronomy determines whether gaseous objects have layers or spherical portions predominantly composed of gas.
Within these spherical portions may occur various gaseous meteors such as clouds, winds, or streams.
Liquid meteors
Liquid water precipitation falls from the atmosphere and reaches the ground, such as drizzle and rain. Suspended liquid water particles may form and remain suspended in the air (damp haze, cloud, fog, and mist), or may be lifted by the wind from the Earth’s surface (blowing spray) causing restrictions to visibility.[10]
Rocky meteors
"A skydiver may have captured the first film ever of a meteorite plunging down at terminal velocity, also known as its “dark flight” stage."[11]
"The footage was captured in 2012 by a helmet cam worn by Anders Helstrup as he and other members of the Oslo Parachute Club jumped from a small plane that took off from an airport in Hedmark, Norway."[11]
“It can’t be anything else. The shape is typical of meteorites -- a fresh fracture surface on one side, while the other side is rounded.”[12]
“It has never happened before that a meteorite has been filmed during dark flight; this is the first time in world history.”[12]
"Having the rock in hand would certainly help. But despite triangulations and analyses, Helstrup and his recruits still haven’t found it."[11]
Meteoroids
Def. a relatively small (sand- to boulder-sized) fragment of debris in a solar system is called a meteoroid.
"As of 2011 the International Astronomical Union officially defines a meteoroid as a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom".[13][14]
The visible path of a meteoroid that enters the Earth's atmosphere (or another body's) atmosphere is called a meteor, or colloquially a shooting star or falling star. If a meteoroid reaches the ground and survives impact, then it is called a meteorite.
Beech and Steel, writing in Quarterly Journal of the Royal Astronomical Society, proposed a new definition where a meteoroid is between 100 µm and 10 m across.[15] Following the discovery and naming of asteroids below 10 m in size (e.g., 2008 TC3), Rubin and Grossman refined the Beech and Steel definition of meteoroid to objects between 10 µm and 1 m in diameter.[16] The [near-Earth object] NEO definition includes larger objects, up to 50 m in diameter, in this category. Very small meteoroids are known as micrometeoroids (see also interplanetary dust).
The composition of meteoroids can be determined as they pass through Earth's atmosphere from their trajectories and the light spectra of the resulting meteor. Their effects on radio signals also give information, especially useful for daytime meteors which are otherwise very difficult to observe.
The light spectra, combined with trajectory and light curve measurements, have yielded various compositions and densities, ranging from fragile snowball-like objects with density about a quarter that of ice,[17] to nickel-iron rich dense rocks.
In meteoroid ablation spheres from deep-sea sediments, "[t]he silicate spheres are the most dominant group."[18]
From these trajectory measurements, meteoroids have been found to have many different orbits, some clustering in streams (see Meteor showers) often associated with a parent comet, others apparently sporadic. Debris from meteoroid streams may eventually be scattered into other orbits. ... Meteoroids travel around the Sun in a variety of orbits and at various velocities. The fastest ones move at about 26 miles per second (42 kilometers per second) through space in the vicinity of Earth's orbit. The Earth travels at about 18 miles per second (29 kilometers per second). Thus, when meteoroids meet the Earth's atmosphere head-on (which would only occur if the meteors were in a retrograde orbit), the combined speed may reach about 44 miles per second (71 kilometers per second). Meteoroids moving through the earth's orbital space average about 20 km/s.[19]
Fireballs
A relatively small percentage of meteoroids hit the Earth's atmosphere and then pass out again: these are termed Earth-grazing fireballs (for example The Great Daylight 1972 Fireball).
For 2011 there are 4589 fireball records at the American Meteor Society.[20]
"At 66 kilometers (41 miles) per second, they appear as fast streaks, faster by a hair than their sisters, the Eta Aquarids of May. And like the Eta Aquarids, the brightest of family tend to leave long-lasting trains. Fireballs are possible three days after maximum."[21]
Bolides
Def. a fireball reaching magnitude −14 or brighter is called a bolide.[22]
Def. a fireball reaching an magnitude −17 or brighter is called a superbolide.
Meteor showers
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Meteors may occur in showers, which arise when the Earth passes through a trail of debris left by a comet, or as "random" or "sporadic" meteors, not associated with a specific single cause. A number of specific meteors have been observed, largely by members of the public and largely by accident.
Cryometeors
A megacryometeor is a very large chunk of ice sometimes called huge hailstones, but do not need to form in thunderstorms.
Lithometeors
Def. a suspension of dry dust in the atmosphere is called a lithometeor.
Def. the solid material thrown into the air by a volcanic eruption that settles on the surrounding areas is called tephra.
Micrometeors
A micrometeoroid is a tiny meteoroid; a small particle of rock in space, usually weighing less than a gram. A micrometeorite is such a particle that survives passage through the Earth's atmosphere and reaches the Earth's surface.
Micrometeoroids are extremely common in space. [These tiny] particles are a major contributor to space weathering processes. When they hit the surface of the Moon, or any airless body (Mercury, the asteroids, etc.), the resulting melting and vaporization causes darkening and other optical changes in the regolith.
Micrometeoroids have less stable orbits than meteoroids, due to their greater surface area to mass ratio.
Micrometeoroids pose a significant threat to space exploration.[23] Their velocities relative to a spacecraft in orbit average 10 kilometers per second (22,500 mph),[23] and resistance to micrometeoroid impact is a significant design challenge for spacecraft and space suit designers (See Thermal Micrometeoroid Garment). While the tiny sizes of most micrometeoroids limits the damage incurred, the high velocity impacts will constantly degrade the outer casing of spacecraft in a manner analogous to sandblasting. Long term exposure can threaten the functionality of spacecraft systems.
Hydrometeors
Def. precipitation products of the condensation of atmospheric water vapour are called hydrometeors.
Def. any or all of the forms of water particles, whether liquid or solid, that fall from the atmosphere are called precipitation.
Particles
The Comprehensive Suprathermal and Energetic Particle Analyzer (COSTEP) aboard SOHO "detects and classifies very energetic particle populations of solar, interplanetary, and galactic origin."[24]
Ionizing radiation
While large objects may induce the gain or loss of charge from another object, ionizing radiation is usually thought of as on the order of or smaller than an atom.
Different types of ionizing radiation behave in different ways, so different shielding techniques are used.
- Particle radiation consists of a stream of charged or neutral particles, both charged ions and subatomic elementary particles. This includes solar wind, cosmic radiation, and neutron flux in nuclear reactors.
- Alpha particles (helium nuclei) are the least penetrating. Even very energetic alpha particles can be stopped by a single sheet of paper.
- Beta particles (electrons) are more penetrating, but still can be absorbed by a few millimeters of aluminum. However, in cases where high energy beta particles are emitted shielding must be accomplished with low density materials, e.g. plastic, wood, water or acrylic glass (Plexiglas, Lucite). This is to reduce generation of Bremsstrahlung X-rays. In the case of beta+ radiation (positrons), the gamma radiation from the electron-positron annihilation reaction poses additional concern.
- Neutron radiation is not as readily absorbed as charged particle radiation, which makes this type highly penetrating. Neutrons are absorbed by nuclei of atoms in a nuclear reaction. This most-often creates a secondary radiation hazard, as the absorbing nuclei transmute to the next-heavier isotope, many of which are unstable.
- Cosmic radiation is not a common concern, as the Earth's atmosphere absorbs it and the magnetosphere acts as a shield, but it poses a problem for satellites and astronauts and frequent fliers are also at a slight risk. Cosmic radiation is extremely high energy, and is very penetrating.
- Electromagnetic radiation consists of emissions of electromagnetic waves, the properties of which depend on the wavelength.
- X-ray and gamma radiation are best absorbed by atoms with heavy nuclei; the heavier the nucleus, the better the absorption. In some special applications, depleted uranium is used, but lead is much more common; several centimeters are often required. Barium sulfate is used in some applications too. However, when cost is important, almost any material can be used, but it must be far thicker. Most nuclear reactors use thick concrete shields to create a bioshield with a thin water cooled layer of lead on the inside to protect the porous concrete from the coolant inside. The concrete is also made with heavy aggregates, such as Baryte, to aid in the shielding properties of the concrete.
- Ultraviolet (UV) radiation is ionizing but it is not penetrating, so it can be shielded by thin opaque layers such as sunscreen, clothing, and protective eyewear. Protection from UV is simpler than for the other forms of radiation above, so it is often considered separately.
In some cases, improper shielding can actually make the situation worse, when the radiation interacts with the shielding material and creates bremsstrahlung secondary radiation that absorbs in the organisms more readily.
Cosmic rays
Cosmic rays are energetic charged subatomic particles, originating in outer space.
At right is an image indicating the range of cosmic-ray energies. The flux for the lowest energies (yellow zone) is mainly attributed to solar cosmic rays, intermediate energies (blue) to galactic cosmic rays, and highest energies (purple) to extragalactic cosmic rays.[25] "Cosmic rays arise from galactic source accelerators."[26]
Cosmic rays may be upwards of a ZeV (1021 eV).
About 89% of cosmic rays are simple protons or hydrogen nuclei, 10% are helium nuclei of alpha particles, and 1% are the nuclei of heavier elements. Solitary electrons constitute much of the remaining 1%.
Def. cosmic rays that originate from astrophysical sources are called primary cosmic rays.
Def. cosmic rays that are created when primary cosmic rays interact with interstellar matter are called secondary cosmic rays.
Def. low energy cosmic rays associated with solar flares are called solar cosmic rays.
Cosmic rays are not charge balanced; that is, positive ions heavily outnumber electrons. The positive ions are
- free protons,
- alpha particles (helium nuclei),
- lithium nuclei,
- beryllium nuclei, and
- boron nuclei.
Neutrals
Neutrals are usually neutral atoms, or molecules. But they also can be neutral subatomic particles such as the neutron, neutral pions, and the neutrino.
Subatomics
Subatomics involves one or more subatomic particles or radiation. The bare nuclei of atoms may qualify as a form of subatomics.
Def.
- particles that are constituents of the atom, or are smaller than an atom; such as proton, neutron, electron, etc or
- any length or mass that is smaller in scale than a the diameter of a hydrogen atom
are called subatomics, or subatomic, respectively.
As a bare uranium nucleus is smaller than a hydrogen atom in diameter, but much larger in mass, it qualifies as one of the subatomics. Here, subatomic is used to mean smaller than the diameter of a hydrogen atom.
Lithium nuclei
The "evidence for the overwhelming majority of the Li-atoms in photospheres has its origin not only in nuclear synthesis near the stellar centers, but also by active processes in stellar atmospheres. [...] the lithium [resonance] line [is] near 478 keV."[27]
"Approximately 90% of lithium atoms originate from α - α reactions for the typical spectra of an accelerated particles on the Sun [...] During impulsive flares, interaction between the accelerated particles and the ambient medium occurs mainly at low altitudes, i.e., close to the footprints of loops."[27]
Alphas
About 89% of cosmic rays are simple protons or hydrogen nuclei, 10% are helium nuclei or alpha particles, and 1% are the nuclei of heavier elements. Solitary electrons constitute much of the remaining 1%.
Helions
Def. a nucleus of a helium-3 atom" is called a helion.
Tritons
Energetic deuterons and tritons have been detected in solar flares.[28]
Deuterons
"The flux [of deuterons in cosmic rays at a geomagnetic latitude of 7.6°N] is found to be 4 ± 1.3 M-2 sec-1 sterad-1".[29]
Baryons
In "dense nuclear matter, such as neutron stars [it] has recently been discovered that kaon condensation in nuclear matter at a density of a few times normal nuclear matter may significantly reduce the upper mass limit of neutron stars [...] This clearly has an impact on astronomical observations. By exploiting the electron fermi level, we are able to predict kaon production at reasonable baryon number densities [...] Experimental detection of [dibaryons, hyperons] is a subtle matter [...] there is strong theoretical evidence that such states [as the dibaryon] do exist in nature. [...] the lightest dibaryon [...] is energetically stable against strong decay to [ΛΛ baryons] by 88 MeV. [The H dibaryon] is bound by 250 MeV."[30]
Radioactivity
Def. a spontaneous emission of an α ray, β ray, or γ ray by the disintegration of an atomic nucleus is called radioactivity.[31]
Although alpha, beta, and gamma radiations were found most commonly, other types of decay were eventually discovered. Shortly after the discovery of the positron in cosmic ray products, it was realized that the same process that operates in classical beta decay can also produce positrons (positron emission). In an analogous process, instead of emitting positrons and neutrinos, some proton-rich nuclides were found to capture their own atomic electrons (electron capture), and emit only a neutrino (and usually also a gamma ray). Each of these types of decay involves the capture or emission of nuclear electrons or positrons, and acts to move a nucleus toward the ratio of neutrons to protons that has the least energy for a given total number of nucleons (neutrons plus protons).
Hadrons
Hadrons are subatomic particles of a type including baryons and mesons that can take part in the strong interaction and may be useful in astronomy.
A hadron, like an atomic nucleus, is a composite particle held together by the strong force Hadrons are categorized into two families: baryons (such as protons and neutrons) and mesons.
Radioactivity emissions
The nuclei of some atoms spontaneously disintegrate from one form of isotope to another until they reach a stable form. These atoms emit particles (alpha or beta) or electromagnetics (X-ray or gamma) which are different in charge, size, penetrating power and ionization energy.
In Template:SubatomicParticle decay, or "positron emission", the weak interaction converts a nucleus into its next-lower neighbor on the periodic table while emitting an positron (Template:SubatomicParticle) and an electron neutrino (Template:SubatomicParticle):
- <math>
^A_ZN \rightarrow ~ ^{~~~A}_{Z-1}N' + e^+ + \nu_e. </math>
Template:SubatomicParticle decay cannot occur in an isolated proton because it requires energy due to the mass of the neutron being greater than the mass of the proton. Template:SubatomicParticle decay can only happen inside nuclei when the value of the binding energy of the mother nucleus is less than that of the daughter nucleus. The difference between these energies goes into the reaction of converting a proton into a neutron, a positron and a neutrino and into the kinetic energy of these particles.
Positron emission' or beta plus decay (β+ decay) is a type of beta decay in which a proton is converted, via the weak force, to a neutron, releasing a positron and a neutrino.
Isotopes which undergo this decay and thereby emit positrons include carbon-11, potassium-40, nitrogen-13, oxygen-15, fluorine-18, and iodine-121. As an example, the following equation describes the beta plus decay of carbon-11 to boron-11, emitting a positron and a neutrino:
- <math>
^{11}_{6}C \rightarrow ~ ^{11}_{5}B + e^+ + \nu_e + \gamma {(0.96 MeV)}. </math>
Antimatter
Def. a subatomic particle corresponding to another particle with the same mass, spin and mean lifetime but with charge, parity, strangeness and other quantum numbers flipped in sign is called an antiparticle.
Def. matter that is composed of antiparticles of those that constitute normal matter is called antimatter.
Annihilations
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production of two or more gamma ray photons.
Def. the process of a particle and its corresponding antiparticle combining to produce energy is called annihilation.
The figure at right shows a positron (e+) emitted from an atomic nucleus together with a neutrino (v). Subsequently, the positron moves randomly through the surrounding matter where it hits several different electrons (e-) until it finally loses enough energy that it interacts with a single electron. This process is called an "annihilation" and results in two diametrically emitted photons with a typical energy of 511 keV each. Under normal circumstances the photons are not emitted exactly diametrically (180 degrees). This is due to the remaining energy of the positron having conservation of momentum.
Electron–positron annihilation occurs when an electron (Template:SubatomicParticle) and a positron (Template:SubatomicParticle, the electron's antiparticle) collide. The result of the collision is the annihilation of the electron and positron, and the creation of gamma ray photons or, at higher energies, other particles:
- Template:SubatomicParticle + Template:SubatomicParticle → Template:SubatomicParticle + Template:SubatomicParticle
The process [does] satisfy a number of conservation laws, including:
- Conservation of electric charge. The net charge before and after is zero.
- Conservation of linear momentum and total energy. This forbids the creation of a single gamma ray. However, in quantum field theory this process is described; see examples of annihilation.
- Conservation of angular momentum.
As with any two charged objects, electrons and positrons may also interact with each other without annihilating, in general by elastic scattering.
The creation of only one photon can occur for tightly bound atomic electrons.[32] In the most common case, two photons are created, each with energy equal to the rest energy of the electron or positron (511 keV).[33] It is also common for three to be created, since in some angular momentum states, this is necessary to conserve C parity.[34] Any larger number of photons can be created, but the probability becomes lower with each additional photon. When either the electron or positron, or both, have appreciable kinetic energies, other heavier particles can also be produced (such as D mesons), since there is enough kinetic energy in the relative velocities to provide the rest energies of those particles. Photons and other light particles [may be produced], but they will emerge with higher energies.
At energies near and beyond the mass of the carriers of the weak force, the W and Z bosons, the strength of the weak force becomes comparable with electromagnetism.[34] It becomes much easier to produce particles such as neutrinos that interact only weakly.
The heaviest particle pairs yet produced by electron–positron annihilation are [[w:W boson|Template:SubatomicParticle–Template:SubatomicParticle]] pairs. The heaviest single particle is the Z boson.
Annihilation radiation is not monoenergetic, unlike gamma rays produced by radioactive decay. The production mechanism of annihilation radiation introduces Doppler broadening.[35] The annihilation peak produced in a gamma spectrum by annihilation radiation therefore has a higher full width at half maximum (FWHM) than other gamma rays in [the] spectrum. The difference is more apparent with high resolution detectors, such as Germanium detectors, than with low resolution detectors such as Sodium iodide Because of their well-defined energy (511 keV) and characteristic, Doppler-broadened shape, annihilation radiation can often be useful in defining the energy calibration of a gamma ray spectrum.
Positroniums
Def. an exotic atom consisting of a positron and an electron, but having no nucleus or an onium consisting of a positron (anti-electron) and an electron, as a particle–anti-particle bound pair is called positronium.
Being unstable, the two particles annihilate each other to produce two gamma ray photons after an average lifetime of 125 ps or three gamma ray photons after 142 ns in vacuum, depending on the relative spin states of the positron and electron.
The singlet state with antiparallel spins ([spin quantum number] S = 0, Ms = 0) is known as para-positronium (p-Ps) and denoted Template:SubatomicParticle. It has a mean lifetime of 125 picoseconds and decays preferentially into two gamma quanta with energy of 511 keV each (in the center of mass frame). Detection of these photons allows for the reconstruction of the vertex of the decay ... Para-positronium can decay into any even number of photons (2, 4, 6, ...), but the probability quickly decreases as the number increases: the branching ratio for decay into 4 photons is 1.439(2)×10−6.[36]
para-positronium lifetime (S = 0):[36]
- <math>t_{0} = \frac{2 \hbar}{m_e c^2 \alpha^5} = 1.244 \times 10^{-10} \; \text{s}</math>
The triplet state with parallel spins (S = 1, Ms = −1, 0, 1) is known as ortho-positronium (o-Ps) and denoted 3S1. The triplet state in vacuum has a mean lifetime of 142.05±0.02 ns[37] and the leading mode of decay is three gamma quanta. Other modes of decay are negligible; for instance, the five photons mode has branching ratio of ~1.0×10−6.[38]
ortho-positronium lifetime (S = 1):[36]
- <math>t_{1} = \frac{\frac{1}{2} 9 h}{2 m_e c^2 \alpha^6 (\pi^2 - 9)} = 1.386 \times 10^{-7} \; \text{s}</math>
Pair production
The reverse reaction, electron–positron creation, is a form of pair production governed by two-photon physics.
Two-photon physics, also called gamma-gamma physics, [studies] the interactions between two photons. If the energy in the center of mass system of the two photons is large enough, matter can be created.[39]
In nuclear physics, [the above reaction] occurs when a high-energy photon interacts with a nucleus. The photon must have enough energy [> 2*511 keV, or 1.022 MeV] to create an electron plus a positron. Without a nucleus to absorb momentum, a photon decaying into electron-positron pair (or other pairs for that matter [such as a muon and anti-muon or a tau and anti-tau] can never conserve energy and momentum simultaneously.[40]
These interactions were first observed in Patrick Blackett's counter-controlled cloud chamber. In 2008 the Titan laser aimed at a 1-millimeter-thick gold target was used to generate positron–electron pairs in large numbers.[41]. "The LLNL scientists created the positrons by shooting the lab's high-powered Titan laser onto a one-millimeter-thick piece of gold."[41]
Neutrons
"Due to the very low energy of the colliding protons in the Sun, only states with no angular momentum (s-waves) contribute significantly. One can consider it as a head-on collision, so that angular momentum plays no role. Consequently, the total angular momentum is the sum of the spins, and the spins alone control the reaction. Because of Pauli's exclusion principle, the incoming protons must have opposite spins. On the other hand, in the only bound state of deuterium, the spins of the neutron and proton are aligned. Hence a spin flip must take place [...] The strength of the nuclear force which holds the neutron and the proton together depends on the spin of the particles. The force between an aligned proton and neutron is sufficient to give a bound state, but the interaction between two protons does not yield a bound state under any circumstances. Deuterium has only one bound state."[42]
The "force acting between the protons and the neutrons [is] the strong force".[42]
"A potential of 36 MeV is needed to get just one energy state."[42]
The width of a bound proton and neutron is "2.02 x 10-13 cm".[42]
Protons
The proton is a subatomic particle with the symbol Template:SubatomicParticle or Template:SubatomicParticle and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number.
Nucleon spin structure describes the partonic structure of proton intrinsic angular momentum (spin). The key question is how the nucleon's spin, whose magnitude is 1/2ħ, is carried by its [suggested] constituent partons (quarks and gluons). In the late 1980s, the European Muon Collaboration (EMC) conducted experiments that suggested the spin carried by quarks is not sufficient to account for the total spin of [protons]. This finding astonished particle physicists at that time, and the problem of where the missing spin lies is sometimes referred to as the "proton spin crisis".
Experimental research on these topics has been continued by the Spin Muon Collaboration (SMC) and the COMPASS experiment at CERN, experiments E154 and E155 at [SLAC National Accelerator Laboratory] SLAC, HERMES at DESY, experiments at [Thomas Jefferson National Accelerator Facility] JLab and RHIC, and others. Global analysis of data from all major experiments confirmed the original EMC discovery and showed that the quark spin [may] contribute about 30% to the total spin of the nucleon.
New measurements performed by European scientists reveal that the radius of the proton is 4 percent smaller than previously estimated.[43]
The antiproton (Template:SubatomicParticle, pronounced p-baer) is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived since any collision with a proton will cause both particles to be annihilated in a burst of energy.
Antiprotons have been detected in cosmic rays for over 25 years, first by balloon-borne experiments and more recently by satellite-based detectors. The standard picture for their presence in cosmic rays is that they are produced in collisions of cosmic ray protons with nuclei in the interstellar medium, via the reaction, where A represents a nucleus:
- Template:SubatomicParticle + A → Template:SubatomicParticle + Template:SubatomicParticle + Template:SubatomicParticle + A
The secondary antiprotons (Template:SubatomicParticle) then propagate through the galaxy, confined by the galactic magnetic fields. Their energy spectrum is modified by collisions with other atoms in the interstellar medium. The antiproton cosmic ray energy spectrum is now measured reliably and is consistent with this standard picture of antiproton production by cosmic ray collisions.[44]
Mesons
Mesons are hadronic subatomic particles, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometre, which is about 2⁄3 the size of a proton or neutron.
Charged mesons decay (sometimes through intermediate particles) to form electrons and neutrinos. Uncharged mesons may decay to photons.
Mesons are not produced by radioactive decay, but appear in nature only as short-lived products of very high-energy interactions in matter In cosmic ray interactions, for example, such particles are ordinary protons and neutrons. Mesons are also frequently produced artificially in high-energy particle accelerators that collide protons, anti-protons, or other particles.
Mesons are subject to "both the weak and strong interactions. Mesons with net electric charge also participate in the electromagnetic interaction.
While no meson is stable, those of lower mass are nonetheless more stable than the most massive mesons, and are easier to observe and study in particle accelerators or in cosmic ray experiments. They are also typically less massive than baryons, meaning that they are more easily produced in experiments, and thus exhibit certain higher energy phenomena more readily than baryons composed of the same quarks would.
Potential mesons to be detected astronomically include: π, ρ, η, η′, φ, ω, J/ψ, ϒ, θ, K, B, D, and T.
Single π0 production occurs "in neutral current neutrino interactions with water by a 1.3 GeV wide band neutrino beam."[45]
"The Gamma-Ray Spectrometer (GRS) on [Solar Maximum Mission] SMM has detected [...] at least two of the flares have spectral properties >40 MeV that require gamma rays from the decay of neutral pions. [Pion] production can occur early in the impulsive phase as defined by hard X-rays near 100 keV."[46]
Gamma-ray "emission matches remarkably well both the position and shape of the inner [supernova remnant] SNR shocked plasma. Furthermore, the gamma-ray spectrum shows a prominent peak near 1 GeV with a clear decrement at energies below a few hundreds of MeV as expected from neutral pion decay."[47]
Beta-particles
Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay. They are designated by the Greek letter beta (β).
Electrons
The electron is a subatomic particle with a negative charge, equal to -1.60217646x10-19 C. Current, or the rate of flow of charge, is defined such that one coulomb, so 1/-1.60217646x10-19, or 6.24150974x1018 electrons flowing past a point per second give a current of one ampere. The charge on an electron is often given as -e. note that charge is always considered positive, so the charge of an electron is always negative.
The electron has a mass of 9.10938188x10-31 kg, or about 1/1840 that of a proton. The mass of an electron is often written as me.
When working, these values can usually be safely approximated to:
- -e = -1.60x10-19 C
- me = 9.11x10-31kg
It has no known components or substructure; in other words, it is generally thought to be an elementary particle.[48][49] The intrinsic angular momentum (spin) of the electron is a half-integer value in units of ħ, which means that it is a fermion.
Def. a quasiparticle produced as a result of electron spin-charge separation is called a chargon.
A chargon possesses the charge of an electron without a spin.
A spinon, in turn, possesses the spin of an electron without charge. The suggestion is that an elementary particle such as a positron may consist of at least two parts: spin and charge.
An electron may be a negative chargon plus a spinon.
Positrons
"The two conversions of protons into neutrons are assumed to take place inside the nucleus, and the extra positive charge is emitted as a positron."[42]
Def. the antimatter equivalent of an electron, having the same mass but a positive charge is called a positron.
Tauons
"For ultrahigh energies the neutrino spectrum at the detector is influenced by neutrino-nucleon interactions and tauon decays during the passage through the interior of the earth."[50]
Def. A lepton is a spin 1/2 particle a fermion that does not interact via the strong force. To date there are three known types of leptons. They are the electron, the muon (<math>\mu</math>), and the tauon (<math>\tau</math>) with their corresponding anti-particles that carry opposite charge (<math>+</math> instead of <math>-</math>).
Muons
"TeV muons from γ ray primaries ... are rare because they are only produced by higher energy γ rays whose flux is suppressed by the decreasing flux at the source and by absorption on interstellar light."[51]
The muon from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with unitary negative electric charge (−1) and a spin of 1⁄2. Together with the electron, the tau, and the three neutrinos, it is classified as a lepton. As is the case with other leptons, the muon is not believed to have any sub-structure at all (i.e., is not thought to be composed of any simpler particles).
The muon is an unstable subatomic particle with a mean lifetime of 2.2 μs. This comparatively long decay lifetime (the second longest known) is due to being mediated by the weak interaction. The only longer lifetime for an unstable subatomic particle is that for the free neutron, a baryon particle composed of quarks, which also decays via the weak force. Muon decay produces three particles, an electron plus two neutrinos of different types.
Like all elementary particles, the muon has a corresponding antiparticle of opposite charge (+1) but equal mass and spin: the antimuon (also called a positive muon). Muons are denoted by Template:SubatomicParticle and antimuons by Template:SubatomicParticle.
Neutrinos
A neutrino is an electrically neutral, weakly interacting elementary subatomic particle[52] with half-integer spin. ... Neutrinos do not carry electric charge, which means that they are not affected by the electromagnetic forces that act on charged particles such as electrons and protons. Neutrinos are affected only by the weak sub-atomic force, of much shorter range than electromagnetism, and gravity, which is relatively weak on the subatomic scale. They are therefore able to travel great distances through matter without being affected by it.
"If neutrinos have negligible rest mass, the present density expected for relic neutrinos from the big bang is nν = 110 (Tγ/2.7 K)3 cm–3 for each two-component species. This is of order the photon density nγ, differing just by a factor 3/11 (i.e. a factor 3/4 because neutrinos are fermions rather than bosons, multiplied by 4/11, the factor by which the neutrinos are diluted when e+–e– annihilation boosts the photon density). This conclusion holds for non-zero masses, provided that mvc2 is far below the thermal energy (~ 5 MeV) at which neutrinos decoupled from other species and that the neutrinos are stable for the Hubble time. Comparison with the baryon density, related to Ω via nb = 1.5 x 10–5 Ωb h2 cm–3, shows that neutrinos outnumber baryons by such a big factor that they can be dynamically dominant over baryons even if their masses are only a few electron volts. In fact, a single species of neutrino would yield a contribution to Ω of Ωv = 0.01 h–2 (mv)eV, so if h = 0.5, only 25 eV is sufficient to provide the critical density."[53]
"Neutrinos of nonzero mass would be dynamically important not only for the expanding universe as a whole but also for large bound systems such as clusters of galaxies. This is because they would now be moving slowly: if the universe had cooled homogeneously, primordial neutrinos would now be moving at around 200 (mv)-1eV km s–1. They would be influenced even by the weak (~ 10–5 c2) gravitational potential fluctuations of galaxies and clusters. If the three (or more) types of neutrinos have different masses, then the heaviest will obviously be gravitationally dominant, since the numbers of each species should be the same."[53]
Electromagnetics
Electromagnetics is most familiar as light, or electromagnetic radiation.
Superluminals
"The existence of superluminal energy transfer has not been established so far, and one may ask why. There is the possibility that superluminal quanta just do not exist, the vacuum speed of light being the definitive upper bound. There is another explanation, the interaction of superluminal radiation with matter is very small, the quotient of tachyonic and electric fine-structure constants being q2/e2 ≈ 1.4 x 10-11 [5], and therefore superluminal quanta are hard to detect."[54]
Cherenkovs
At right is an example of Cherenkov radiation. Cherenkov radiation (also spelled Čerenkov) is electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium at a speed greater than the phase velocity of light in that medium. Cherenkov radiation is an example of medium specific superluminals.
Entities
The electron is a subatomic particle with a negative charge, equal to -1.60217646x10-19 C. Current, or the rate of flow of charge, is defined such that one coulomb, so 1/-1.60217646x10-19, or 6.24150974x1018 electrons flowing past a point per second give a current of one ampere. The charge on an electron is often given as -e. note that charge is always considered positive, so the charge of an electron is always negative.
Sources
- ↑ 1.0 1.1 1.2 1.3 Safi Bahcall, Bryan W. Lynn, and Stephen B. Selipsky (1990). "New Models for Neutron Stars". The Astrophysical Journal. 362 (10): 251–5. Bibcode:1990ApJ...362..251B. doi:10.1086/169261. Retrieved 2014-01-11. Unknown parameter
|month=ignored (help) - ↑ Richard Powell (30 July 2006). The Universe within 1 billion Light Years The Neighbouring Superclusters. Atlas of the Universe. Retrieved 2018-04-01.
- ↑ 3.0 3.1 M. Gregg (3 March 2005). "The Impending Destruction of NGC 1427A". Baltimore, Maryland USA: Hubblesite.org. Retrieved 2016-11-05.
- ↑ Juna A. Kollmeier and Andrew Gould (2007). "Where Are the Old-Population Hypervelocity Stars?". The Astrophysical Journal. 664 (1): 343–8. doi:10.1086/518405. Retrieved 2012-03-05. Unknown parameter
|month=ignored (help) - ↑ Martin, Christopher; Seibert, M; Neill, JD; Schiminovich, D; Forster, K; Rich, RM; Welsh, BY; Madore, BF; Wheatley, JM (August 17, 2007). "A turbulent wake as a tracer of 30,000 years of Mira's mass loss history". Nature. 448 (7155): 780–783. Bibcode:2007Natur.448..780M. doi:10.1038/nature06003. PMID 17700694.
|access-date=requires|url=(help) - ↑ Minkel, JR."Shooting Bullet Star Leaves Vast Ultraviolet Wake", "The Scientific American", August 15, 2007 Accessed August 21, 2007.
- ↑ Christopher Wareing, A. A. Zijlstra, T. J. O'Brien, M. Seibert (November 6, 2007). "It's a wonderful tail: the mass-loss history of Mira". Astrophysical Journal Letters. 670 (2): L125–L129. arXiv:0710.3010. Bibcode:2007ApJ...670L.125W. doi:10.1086/524407.
- ↑ W. Clavin (August 15, 2007). GALEX finds link between big and small stellar blasts. California Institute of Technology. Retrieved 2007-08-16.
- ↑ Christopher Wareing (December 13, 2008). "Wonderful Mira". Philosophical Transactions of the Royal Society A. 366 (1884): 4429–40. Bibcode:2008RSPTA.366.4429W. doi:10.1098/rsta.2008.0167. PMID 18812301.
- ↑ Mark R. Mireles, Kirth L. Pederson, Charles H. Elford (February 21, 2007). Meteorologial Techniques. 106 Peacekeeper Drive, Suite 2N3, Offutt Air Force Base, Nebraska USA: Air Force Weather Agency/DNT. Retrieved 2013-02-17.
- ↑ 11.0 11.1 11.2 Janet Fang (April 4, 2014). Skydiver Almost Hit by Meteorite. IFLScience. Retrieved 2014-08-31.
- ↑ 12.0 12.1 Hans Erik Foss Amundsen (April 4, 2014). Skydiver Almost Hit by Meteorite. IFLScience. Retrieved 2014-08-31.
- ↑ Peter M. Millman (1961). "A report on meteor terminology". JRASC. 55: 265–267. Bibcode:1961JRASC..55..265M.
- ↑ Glossary International Meteor Organization. Imo.net. 2008-11-18. Retrieved 2011-09-16.
- ↑ Martin Beech, Duncan Steel (1995). "On the Definition of the Term Meteoroid". Quarterly Journal of the Royal Astronomical Society. 36 (3): 281–284. Bibcode:1995QJRAS..36..281B. Unknown parameter
|month=ignored (help)) - ↑ Rubin, A.E. (2010). "Meteorite and meteoroid: New comprehensive definitions". Meteoritics & Planetary Science. 45 (1): 114–122. Bibcode:2010M&PS...45..114R. doi:10.1111/j.1945-5100.2009.01009.x. Unknown parameter
|coauthors=ignored (help); Unknown parameter|month=ignored (help)) - ↑ Povenmire, H. PHYSICAL DYNAMICS OF THE UPSILON PEGASID FIREBLL – EUROPEAN NETWORK 190882A. Florida Institute of Technology
- ↑ M.B. Blanchard, D.E. Brownlee, T.E. Bunch, P.W. Hodge, F.T. Kyte (1980). "Meteoroid ablation spheres from deep-sea sediments". Earth and Planetary Science Letters. 46 (2): 178–90. doi:10.1016/0012-821X(80)90004-7. Retrieved 2012-01-02. Unknown parameter
|month=ignored (help) - ↑ Report on Orbital Debris. NASA Technical Reports Server. Retrieved 1 September 2012.
- ↑ Fireball Report: 4589 records found between 2011-01-01 and 2011-12-31. American Meteor Society. Retrieved 2012-04-24.
- ↑ David Levy and Stephen Edberg. Observe: Meteors. Astronomical League.
|access-date=requires|url=(help) - ↑ MJS Belton (2004). Mitigation of hazardous comets and asteroids. Cambridge University Press. ISBN 0-521-82764-7.:156
- ↑ 23.0 23.1 Micrometeoroids and Orbital Debris (MMOD) - NASA - White Sands Test Facility, Las Cruces, NM [1]
- ↑ B. Heber (30 June 2003). SOHO Fact Sheet (PDF). Greenbelt, MD 20771, USA: NASA/GSFC. Retrieved 2016-03-27.
- ↑ 25.0 25.1 S. Swordy (2001). "The energy spectra and anisotropies of cosmic rays". Space Science Reviews. 99: 85–94.
- ↑ S. Y. Lee (2004). Accelerator physics, Second Edition. Singapore: World Scientific Publishing Co. Pte. Ltd. p. 575. ISBN 981-256-182-X. Retrieved 2011-12-17.
- ↑ 27.0 27.1 M. A. Livshits (1997). "The Amount of Lithium Produced during Impulsive Flares". Solar Physics. 173 (2): 377–81. doi:10.1023/A:1004958522216. Retrieved 2014-10-01. Unknown parameter
|month=ignored (help) - ↑ P. S. Freier and C. J. Waddington (1963). Energetic Deuterons and Tritons produced by Solar Flares, In: Solar Particles and Sun-Earth Relations. 1. p. 139. Bibcode:1963ICRC....1..139F. Retrieved 2014-10-01.
- ↑ K. M. V. Apparao (1973). Flux of Cosmic Ray Deuterons with Rigidity Above 16.8 GV, In: Proceedings of the 13th International Conference on Cosmic Rays. 1. pp. 126–9. Bibcode:1973ICRC....1..126A. Retrieved 2014-09-30.
- ↑ Karl Michael Westerberg (1996). "Hyperon Calculations in the Skyrme Model". Dissertation Abstracts International. 57-04 (B): 2542. Retrieved 2014-10-03.
- ↑ Philip B. Gove, ed. (1963). Webster's Seventh New Collegiate Dictionary. Springfield, Massachusetts: G. & C. Merriam Company. p. 1221.
|access-date=requires|url=(help) - ↑ L. Sodickson, W. Bowman, J. Stephenson, R. Weinstein (1960). "Single-Quantum Annihilation of Positrons". Physical Review. 124: 1851. Bibcode:1961PhRv..124.1851S. doi:10.1103/PhysRev.124.1851.
- ↑ W.B. Atwood, P.F. Michelson, S.Ritz (2008). "Una Ventana Abierta a los Confines del Universo". Investigación y Ciencia. 377: 24–31.
- ↑ 34.0 34.1 D.J. Griffiths (1987). Introduction to Elementary Particles. John Wiley & Sons. ISBN 0-471-60386-4.
- ↑ Gilmore, G., and Hemmingway, J.: "Practical Gamma Ray Spectrometry", page 13. John Wiley & Sons Ltd., 1995
- ↑ 36.0 36.1 36.2 Savely G. Karshenboim (2003). "Precision Study of Positronium: Testing Bound State QED Theory". International Journal of Modern Physics A [Particles and Fields; Gravitation; Cosmology; Nuclear Physics]. 19 (23): 3879–96. arXiv:hep-ph/0310099. Bibcode:2004IJMPA..19.3879K. doi:10.1142/S0217751X04020142.
- ↑ A. Badertscher; et al. (2007). "An Improved Limit on Invisible Decays of Positronium". Physical Review D. 75 (3): 032004. arXiv:hep-ex/0609059. Bibcode:2007PhRvD..75c2004B. doi:10.1103/PhysRevD.75.032004.
- ↑ Andrzej Czarnecki, Savely G. Karshenboim (1999). "Decays of Positronium". B.B. Levchenko and V.I. Savrin (eds.), Proc. of the th International Workshop on High Energy Physics and Quantum Field Theory (QFTHEP, Moscow , MSU-Press 2000, pp. 538 - 44. 14 (99). arXiv:hep-ph/9911410. Bibcode:1999hep.ph...11410C.
- ↑ Moffat JW (1993). "Superluminary Universe: A Possible Solution to the Initial Value Problem in Cosmology". Intl J Mod Phys D. 2 (3): 351–65. arXiv:gr-qc/9211020. Bibcode:1993IJMPD...2..351M. doi:10.1142/S0218271893000246.
- ↑ Hubbell, J. H. (2006). "Electron positron pair production by photons: A historical overview". Radiation Physics and Chemistry. 75 (6): 614–623. Bibcode:2006RaPC...75..614H. doi:10.1016/j.radphyschem.2005.10.008. Unknown parameter
|month=ignored (help) - ↑ 41.0 41.1 Laser technique produces bevy of antimatter. 2008. Retrieved 2008-12-04.
- ↑ 42.0 42.1 42.2 42.3 42.4 Giora Shaviv (2013). Giora Shaviv, ed. Towards the Bottom of the Nuclear Binding Energy, In: The Synthesis of the Elements. Berlin: Springer-Verlag. pp. 169–94. doi:10.1007/978-3-642-28385-7_5. ISBN 978-3-642-28384-0. Retrieved 2013-12-19.
- ↑ Proton's radius revised downward. ScienceNews. 23 February 2013. Retrieved 22 April 2013.
- ↑ Dallas C. Kennedy (2000). "Cosmic Ray Antiprotons". Proc. SPIE. 2806: 113. arXiv:astro-ph/0003485. doi:10.1117/12.253971.
- ↑ S. Nakayama, C. Mauger, M.H. Ahn, S. Aoki, Y. Ashie, H. Bhang, S. Boyd, D. Casper, J.H. Choi, S. Fukuda, Y. Fukuda, R. Gran, T. Hara, M. Hasegawa, T. Hasegawa, K. Hayashi, Y. Hayato, J. Hill, A.K. Ichikawa, A. Ikeda, T. Inagaki, T. Ishida, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H.I. Jang, J.S. Jang, E.J. Jeon, K.K. Joo, C.K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, A. Kibayashi, D. Kielczewska, B.J. Kim, C.O. Kim, J.Y. Kim, S.B. Kim, K. Kobayashi, T. Kobayashi, Y. Koshio, W.R. Kropp, J.G. Learned, S.H. Lim, I.T. Lim, H. Maesaka, T. Maruyama, S. Matsuno, C. Mcgrew, A. Minamino, S. Mine, M. Miura, K. Miyano, T. Morita, S. Moriyama, M. Nakahata, K. Nakamura, I. Nakano, F. Nakata, T. Nakaya, T. Namba, R. Nambu, K. Nishikawa, S. Nishiyama, K .Nitta, S. Noda, Y. Obayashi, A. Okada, Y. Oyama, M.Y. Pac, H. Park, C. Saji, M. Sakuda, A. Sarrat, T. Sasaki, N. Sasao, K. Scholberg, M. Sekiguchi, E. Sharkey, M. Shiozawa, K.K. Shiraishi, M. Smy, H.W. Sobel, J.L. Stone, Y. Suga, L.R. Sulak, A. Suzuki, Y. Suzuki, Y. Takeuchi, N. Tamura, M. Tanaka, Y. Totsuka, S. Ueda, M.R. Vagins, C.W. Walter, W. Wang, R.J. Wilkes, S. Yamada, S. Yamamoto, C. Yanagisawa, H. Yokoyama, J. Yoo, M. Yoshida, and J. Zalipska (2005). "Measurement of single π0 production in neutral current neutrino interactions with water by a 1.3 GeV wide band muon neutrino beam" (PDF). Physics Letters B. 619 (3–4): 255–62. Retrieved 2014-03-22. Unknown parameter
|month=ignored (help) - ↑ Forrest, D. J., Vestrand, W. T., Chupp, E. L., Rieger, E., Cooper, J. F., & Share, G. H. (August 1985). Neutral Pion Production in Solar Flares, In: 19th International Cosmic Ray Conference. 4. NASA. pp. 146–9. Bibcode:1985ICRC....4..146F. Retrieved 2014-10-01.
- ↑ A. Giuliani, M. Cardillo, M. Tavani, Y. Fukui, S. Yoshiike, K. Torii, G. Dubner, G. Castelletti, G. Barbiellini, A. Bulgarelli, P. Caraveo, E. Costa, P.W. Cattaneo, A. Chen, T. Contessi, E. Del Monte, I. Donnarumma, Y. Evangelista, M. Feroci, F. Gianotti, F. Lazzarotto, F. Lucarelli, F. Longo, M. Marisaldi, S. Mereghetti, L. Pacciani, A. Pellizzoni, G. Piano, P. Picozza, C. Pittori, G. Pucella, M. Rapisarda, A. Rappoldi, S. Sabatini, P. Soffitta, E. Striani, M. Trifoglio, A. Trois, S. Vercellone, F. Verrecchia, V. Vittorin, S. Colafrancesco, P. Giommi, and G. Bignami (2011). "Neutral Pion Emission from Accelerated Protons in the Supernova Remnant W44". The Astrophysical Journal Letters. 742 (2): L30. doi:10.1088/2041-8205/742/2/L30. Retrieved 2014-10-02. Unknown parameter
|month=ignored (help) - ↑ E.J. Eichten, M.E. Peskin, M. Peskin (1983). "New Tests for Quark and Lepton Substructure". Physical Review Letters. 50 (11): 811–814. Bibcode:1983PhRvL..50..811E. doi:10.1103/PhysRevLett.50.811.
- ↑ G. Gabrielse; et al. (2006). "New Determination of the Fine Structure Constant from the Electron g Value and QED". Physical Review Letters. 97 (3): 030802(1–4). Bibcode:2006PhRvL..97c0802G. doi:10.1103/PhysRevLett.97.030802.
- ↑ Hettlage, C.; Mannheim, K. (1999). "Tau Sources in the Sky". AG Abstract Services. 15 (04). Bibcode:1999AGM....15..I04H. Retrieved 2014-10-02. Unknown parameter
|month=ignored (help) - ↑
- ↑ Neutrino, In: Glossary for the Research Perspectives of the Max Planck Society. Max Planck Gesellschaft. Retrieved 2012-03-27.
- ↑ 53.0 53.1 Martin J. Rees (1984). "Is the Universe flat?". Journal of Astrophysics and Astronomy. 5 (4): 331–48. Retrieved 2013-12-18. Unknown parameter
|month=ignored (help) - ↑ R Tomaschitz (2010). "Superluminal spectral densities of ultra-relativistic electrons in intense electromagnetic wave fields" (PDF). Applied Physics B Lasers and Optics. 101 (1–2): 143–64. doi:10.1007/s00340-010-4182-8. Retrieved 2012-03-21. Unknown parameter
|month=ignored (help); Unknown parameter|pdf=ignored (help)