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Particle Shower
In particle physics, a shower is a cascade of secondary particles produced as the result of a high-energy particle interacting with dense matter. The incoming particle interacts, producing multiple new particles with lesser energy; each of these then interacts, in the same way, a process that continues until many thousands, millions, or even billions of low-energy particles are produced. These are then stopped in the matter and absorbed. Types There are two basic types of showers. ''Electromagnetic showers'' are produced by a particle that interacts primarily or exclusively via the electromagnetic force, usually a photon or electron. ''Hadronic showers'' are produced by hadrons (i.e. nucleons and other particles made of quarks), and proceed mostly via the strong nuclear force. Electromagnetic showers An electromagnetic shower begins when a high-energy electron, positron or photon enters a material. At high energies (above a few MeV), in which the photoelectric effect and C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Physics
Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, 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 combinations of protons and neutrons 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 Generation (particle physics), generations of fermions, although ordinary matter is made only from the first fermion generation. The first generation consists of Up quark, 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, the weak interaction, and the strong interaction. Quark, Quarks cannot exist on their own but form hadrons. Hadrons that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Nucleus
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford at the Department_of_Physics_and_Astronomy,_University_of_Manchester , University of Manchester based on the 1909 Geiger–Marsden experiments, Geiger–Marsden gold foil experiment. After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg. An atom is composed of a positively charged nucleus, with a cloud of negatively charged electrons surrounding it, bound together by electrostatic force. Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud. Protons and neutrons are bound together to form a nucleus by the nuclear force. The diameter of the nucleus is in the range of () for hydrogen (the diameter of a single proton) to about for uranium. These dimensions are much ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorescence
Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colored visible light. The color of the light emitted depends on the chemical composition of the substance. Fluorescent materials generally cease to glow nearly immediately when the radiation source stops. This distinguishes them from the other type of light emission, phosphorescence. Phosphorescent materials continue to emit light for some time after the radiation stops. This difference in duration is a result of quantum spin effects. Fluorescence occurs when a photon from incoming radiation is absorbed by a molecule, exciting it to a higher energy level, followed by the emission of light as the molecule returns to a lower energy state. The emitted light may have a longer wavelength and, therefore, a lower photon energy than the absorbed radi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fly's Eye
The High Resolution Fly's Eye or HiRes detector was an ultra-high-energy cosmic ray observatory that operated in the West Desert of Utah from 1981 until April 2006. HiRes (HiRes-I, HiRes-II, and HiRes prototype) used the "atmospheric fluorescence" technique that was pioneered by the Utah group first in tests at the Volcano Ranch experiment and then with the original Fly's Eye experiment. The experiment first ran as the HiRes prototype in a tower configuration operating in conjunction with the CASA (Chicago Air Shower Array) and MIA (Michigan Muon Array). The prototype was later reconfigured to view 360 degrees in azimuth. HiRes-II followed later and was located on a hilltop about 13km away. HiRes-I and HiRes-II operated in stereo. In 1991 it discovered the Oh-My-God Particle. Hardware and development The High Resolution Fly's Eye used larger mirrors and smaller pixels as compared with the original Fly's Eye, hence the name. A prototype of the HiRes experiment operated between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultra-high-energy Cosmic Ray
In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray with an energy greater than 1 EeV (1018 electronvolts, approximately 0.16 joules), far beyond both the rest mass and energies typical of other cosmic ray particles. The origin of these highest energy cosmic rays is not known. These particles are extremely rare; between 2004 and 2007, the initial runs of the Pierre Auger Observatory (PAO) detected 27 events with estimated arrival energies above , that is, about one such event every four weeks in the area surveyed by the observatory. Observational history The first observation of a cosmic ray particle with an energy exceeding (16 J) was made by John Linsley and Livio Scarsi at the Volcano Ranch experiment in New Mexico in 1962. Cosmic ray particles with even higher energies have since been observed. Among them was the Oh-My-God particle observed by the University of Utah's Fly's Eye experiment on the evening of 15 October 1991 over ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pion
In particle physics, a pion (, ) or pi meson, denoted with the Greek alphabet, Greek letter pi (letter), pi (), is any of three subatomic particles: , , and . Each pion consists of a quark and an antiquark and is therefore a meson. Pions are the lightest mesons and, more generally, the lightest hadrons. They are unstable, with the charged pions and decaying after a mean lifetime of 26.033 nanoseconds ( seconds), and the neutral pion decaying after a much shorter lifetime of 85 attoseconds ( seconds). Charged pions most often particle decay, decay into muons and muon neutrinos, while neutral pions generally decay into gamma rays. The exchange of virtual particle, virtual pions, along with vector meson, vector, rho meson, rho and omega mesons, provides an explanation for the nuclear force, residual strong force between nucleons. Pions are not produced in radioactive decay, but commonly are in high-energy collisions between hadrons. Pions also result from some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muon
A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of ''ħ'', but with a much greater mass. It is classified as a lepton. As with other leptons, the muon is not thought to be composed of any simpler particles. The muon is an unstable subatomic particle with a mean lifetime of , much longer than many other subatomic particles. As with the decay of the free neutron (with a lifetime around 15 minutes), muon decay is slow (by subatomic standards) because the decay is mediated only by the weak interaction (rather than the more powerful strong interaction or electromagnetic interaction), and because the mass difference between the muon and the set of its decay products is small, providing few kinetic degrees of freedom for decay. Muon decay almost always produces at least three particles, which must include an electron of the same charge as the muon and t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Shower (physics)
Air showers are extensive Particle shower, cascades of subatomic particles and ionized nuclei, produced in the Earth's atmosphere, atmosphere when a ''primary'' cosmic ray enters the atmosphere. Particles of cosmic radiation can be protons, Atomic nucleus, nuclei, electrons, photons, or (rarely) positrons. Upon entering the atmosphere, they interact with molecules and initiate a particle cascade that lasts for several generations, until the energy of the primary particle is fully converted. If the primary particle is a hadron, mostly light mesons like pions and kaons are produced in the first interactions, which then fuel a hadronic shower component that produces shower particles mostly through pion decay. Primary photons and electrons, on the other hand, produce mainly electromagnetic showers. Depending on the energy of the primary particle, the detectable size of the shower can reach several kilometers in diameter. The air shower phenomenon was unknowingly discovered by Bruno Ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Ray
Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own galaxy, and from distant galaxies. Upon impact with Earth's atmosphere, cosmic rays produce showers of secondary particles, some of which reach the surface, although the bulk are deflected off into space by the magnetosphere or the heliosphere. Cosmic rays were discovered by Victor Hess in 1912 in balloon experiments, for which he was awarded the 1936 Nobel Prize in Physics. Direct measurement of cosmic rays, especially at lower energies, has been possible since the launch of the first satellites in the late 1950s. Particle detectors similar to those used in nuclear and high-energy physics are used on satellites and space probes for research into cosmic rays. Data from the Fermi Space Telescope (2013) have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Interaction Length
Nuclear interaction length is the mean distance travelled by a hadronic particle before undergoing an inelastic nuclear interaction. See also * Nuclear collision length *Radiation length In particle physics, the radiation length is a characteristic of a material, related to the energy loss of high energy elementary particle, particles electromagnetically interacting with it. It is defined as the mean length (in cm) into the mate ... External linksParticle Data Group site Experimental particle physics {{Nuclear-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molière Radius
The Molière radius is a characteristic constant of a material giving the scale of the transverse dimension of the fully contained Particle shower, electromagnetic showers initiated by an incident high energy electron or photon. By definition, it is the radius of a cylinder containing on average 90% of the shower's energy deposition. Two Molière radii contain 95% of the shower's energy deposition. It is related to the radiation length by the approximate relation , where is the atomic number. The Molière radius is useful in experimental particle physics in the design of calorimeter (particle physics), calorimeters: a smaller Molière radius means better shower position resolution, and better shower separation due to a smaller degree of shower overlaps. The Molière radius is named after German physicist Gert Molière, Paul Friederich Gaspard Gert Molière (1909–64).Phillip R. Sloan, Brandon Fogel, "Creating a Physical Biology: The Three-Man Paper and Early Molecular Biology" U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Energy
''Critical Energy'' is a live album by Threshold, released in 2004. Track list Disc 1 # "Phenomenon" (6.06) # "Oceanbound" (6.25) # "Choices" (8.41) # "Angels" (6.47) # "Falling Away" (7.09) # "Virtual Isolation" (6.10) # "Innocent" (4.21) # "Long Way Home" (6.06) # "Fragmentation" (7.00) Disc 2 # "Clear" (3.41) # "Life Flow" (3.53) # "Narcissus" (6.03) # "Sunseeker" (5.25) # "The Latent Gene" (7.57) # "Light And Space" (6.15) # "Sunrise On Mars" (5.29) # "Paradox" (9.25) # "Sanity's End" (10.16) DVD features *Complete concert footage (approx. 2 hours) *Stereo and 5.1 surround sound *Commentary by Karl Groom and Richard West *Critical Moments tour documentary *Additional concert footage from ProgPower USA 2002: Light And Space / The Latent Gene / The Ravages Of Time *Photo gallery by Sy Wooks Seddon Musicians * Andrew McDermott - vocals * Karl Groom - guitar * Nick Midson - guitar * Richard West - keyboard * Steve Anderson - bass guitar * Johanne James ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
