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Topic: Pair production

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	Pair Production (Site not responding. Last check: 2007-10-03)
		Pair production is the formation or materialization of two electrons, one negative and the other positive (positron), from a pulse of electromagnetic energy traveling through matter, usually in the vicinity of an atomic nucleus.
		For pair production to occur, the electromagnetic energy, in a discrete quantity called a photon, must be at least equivalent to the mass of two electrons.
		If pair production occurs in a track detector, such as a cloud chamber, to which a magnetic field is properly applied, the electron and the positron curve away from the point of formation in opposite directions in arcs of equal curvature.
	abyss.uoregon.edu /~js/glossary/pair_production.html (234 words)

	Pair production - Wikipedia, the free encyclopedia
		Pair production refers to the creation of an elementary particle and its antiparticle, usually from a photon (or another neutral boson).
		Pair production is the chief method by which energy from gamma rays is observed in condensed matter.
		In semiclassical general relativity, pair production is also invoked to explain the Hawking radiation effect.
	en.wikipedia.org /wiki/Pair_production (355 words)

	Pair production by photons in the field of the nucleus
		Pair production by photons in the field of the nucleus
		The injection rate of pairs for a given energy of iron nuclei was numerically calculated by Bednarek and Karakula (1995) for an anisotropic photon field from the polar cap.
		Plots of accumulative number of pairs produced per ion through interaction with thermal photons as a function of distance from the polar cap are shown in Figure 4.
	www.atnf.csiro.au /pasa/15_2/luo/paper/node3.html (517 words)

	The Pair Telescope
		The pair telescope is a technology which in its original form as a spark chamber was borrowed directly from the world of high-energy physics.
		By reconstructing the tracks of the charged pair as it passes through the vertical series of trackers, the gamma-ray direction and therefore its origin on the sky are calculated.
		In addition, through the analysis of the scattering of the pair (which is an energy dependent phenomenon) or through the absorption of the pair by a scintillator detector or a calorimeter after they exit the spark chamber, the total energy of the initial gamma-ray is determined.
	imagine.gsfc.nasa.gov /docs/science/how_l2/pair_telescopes.html (1099 words)

	McGraw-Hill AccessScience: Electron-positron pair production
		Electron-positron pair production is an example of the materialization of energy predicted by special relativity and is accurately described by quantum electrodynamics.
		Pair production usually refers to external pair production, in which the positron (positively charged antielectron) and electron are created from a high-energy gamma ray as it passes through matter.
		Electron-positron pairs are also produced from internal pair conversions in nuclei, decays of unstable subatomic particles, and collisions between charged particles.
	www.accessscience.com /Encyclopedia/2/22/Est_224710_frameset.html (156 words)

	Pair production (Site not responding. Last check: 2007-10-03)
		What it does is to say that the positron from pair production will collide with an electron to produce two 0.511 Mev photons.
		The data for pair production is therefore handled as follows.
		The cross sections for pair and triplet production are separated in the
	nuclear.llnl.gov /CNP/mcapm/mcf/node16.html (88 words)

	Lecture 44: The First Three Minutes
		When the universe was less than 0.0001 second old, the photons of the cosmic background were so energetic, proton-antiproton pairs were continuously being formed by pair production.
		Pair production of protons stops (the photons have dropped below the necessary energy), but the annihilation of protons continues.
		The production of electrons is very slightly favored over the production of positrons (just as the production of protons is favored over that of antiprotons, and the production of neutrons is favored over that of antineutrons).
	www-astronomy.mps.ohio-state.edu /~ryden/ast162_10/notes44.html (1559 words)

	Measurement of the WW cross section
		Tevatron the W boson pairs can be produced in two different processes, via the exchange of a quark or in resonant production via a photon (γ;) or Z boson, which are illustrated on the right.
		In most of the collisons the final state consists of quarks and since the direct production of quarks happens more than one million times more often than the pair production of W bosons, it is impossible to distinguish the W bosons that decay into quarks from direct quark production.
		To measure the cross section of the WW pair production we have to carefully estimate the background contributions from all possible processes.
	www-d0.fnal.gov /Run2Physics/WWW/results/final/EW/E04A/E04A.htm (1174 words)

	Numerical Treatment of Lepton Pair Production
		In particular, a copious amount of electron-positron pairs is expected to be produced at each of the interaction regions at RHIC.
		The purpose of this project is to use the T3E to solve numerically the time-dependent Dirac equation that describes the production of electron-positron pairs in relativistic heavy ion collisions.
		In these production runs, we limited the energy of the collision to up to 10 GeV/n, where we have the best handle on the level of precision and time integration of the computer code.
	www.nersc.gov /news/annual_reports/annrep98/belkacem.html (503 words)

	DAMOCLES: Electron-phonon scattering and pair production rates in Si
		Pair production rate: Another hard numerical problem, but the solution had been staring at us since 1967...
		The latter process, known as "impact ionization" or "pair production", consists of an energetic electron "hitting" an electron in the valence band, exciting this electron across the band-gap (about 1.1 eV in Si at 300K), thus generating an electron-hole pair and recoiling to a lower energy state.
		By counting the pairs, and thus measuring the pair-generation-yield (called "quantum yield") as a function of gate bias (and so, of electron energy in the Si substrate), one has a direct measurement of the relative probability that an electron loses energy to phonons rather to electron-hole pairs.
	www.research.ibm.com /DAMOCLES/html_files/sirates.html (3699 words)

	Extreme Rules (Site not responding. Last check: 2007-10-03)
		All code to be included in a production release is created by two people working together at a single computer.
		Pair programming increases software quality without impacting time to deliver.
		The best way to pair program is to just sit side by side in front of the monitor.
	www.extremeprogramming.org /rules/pair.html (147 words)

	Pair Production
		A high speed gamma ray is projected at a nucleus of matter (e.g.
		Each gamma ray photon loses its energy (hf), when it collides with the nucleus, producing an electron positron pair.
		Some of the energy is converted into the mass of the electron and positron.
	homepage.eircom.net /~louiseboylan/Pages/pair_prod.htm (77 words)

	Leptons
		On the other hand, one of the mechanisms for the interaction of radiation with matter is the pair production of an electron-positron pair.
		When a photon has quantum energy higher than the rest mass energy of an electron plus a positron, one of the ways that such a photon interacts with matter is by producing and electron-positron pair.
		For photon energies far above this threshold, pair production becomes the dominant mode for the interaction of x-rays and gamma-rays with matter.
	hyperphysics.phy-astr.gsu.edu /hbase/particles/lepton.html (635 words)

	Relativistic Energy
		The quantum energies of the gamma rays is equal to the sum of the mass energies of the two particles (including their kinetic energies).
		It is also possible for a photon to give up its quantum energy to the formation of a particle-antiparticle pair in its interaction with matter.
		The rest mass energy of an electron is 0.511 MeV, so the threshold for electron-positron pair production is 1.02 MeV.
	hyperphysics.phy-astr.gsu.edu /hbase/relativ/releng.html (350 words)

	Fermion-Pair Production
		The Fermion-Pair Production analysis group is devoted to the measurement of cross-sections and forward-backward asymmetries at LEP2 energies.
		ALEPH Collab., Study of Fermion pair production in e+e- collisions at 130-183 GeV
		The aim (for fermion-pair production) is to improve both on the generators and on the theory programs.
	l3.web.cern.ch /l3/analysis/ffpair (729 words)

	Pair production
		But pair creation in matter occurs in the electromagnetic field of the nucleus, and this is very important.
		Well, for the purpose of understanding why photons cannot produce neutrino-antineutrino pairs at low energy, it is a vey sufficient approximation to assume they have no mass.
		In this way, the process of neutrino pair production by light is allowed, but it must proceed through intermediaries.
	www.physicsforums.com /showthread.php?t=104729 (1123 words)

	Re: Why pair-production cannot take place in vacuum?
		The reason why a gamma-ray cannot create electron-positron pairs in a vacuum is that there is no way to do this without violating the conservation laws.
		Obviously, the argument is the same for the creation of proton-antiproton pairs, etc. If we started with two gamma-rays moving in opposite directions, then the gamma-rays could collide with each other, and create a particle- antiparticle pair.
		The sum of the energies of the two gamma-rays is the smallest in the coordinate system in which their total momentum is zero.
	www.madsci.org /posts/archives/mar97/858809729.Ph.r.html (450 words)

	Pair Telescopes: Quiz
		Pair production is the dominant physical reaction of materials to gamma-rays above:
		What "type" of pair is created in pair production:
		In a pair telescope, an anti-coincidence shield is used to:
	imagine.gsfc.nasa.gov /docs/science/quiz_l2/pair_telescopes_quiz.html (141 words)

	High-Energy Approximation for On-Shell W-Pair Production -- from Mathematica Information Center
		High-Energy Approximation for On-Shell W-Pair Production -- from Mathematica Information Center
		Starting from the exact virtual and soft-photonic O(alpha) corrections to the differential cross section for on-shell W-pair production we derive a high-energy approximation valid for energies much higher than the W-boson mass.
		This approximation is improved by taking into account extra terms for large top-quark and Higgs-boson masses as well as the exact results for the leading low-energy universal corrections associated with the running of alpha and the p-parameter.
	library.wolfram.com /infocenter/Articles/2232 (121 words)

	Pair-of-Dice Games News
		Note: The results of this poll may affect future game publications.
		To better reflect the costs of production, Pair-of-Dice Games will be adjusting its pricing structure effective immediately.
		After recently analyzing the cost involved in producing each game, it became clear that while some games were properly priced, other games needed it's priced adjusted.
	www.pair-of-dice.com /news.html (363 words)

	Pair Production Cross-Sections
		name Phil G. status other age old Question - Pair production cross-sections If two particles, with kinetic energy (in the centre of mass frame) exceeding 2mc^2, collide sufficient surplus mass-energy is available to produce an electron-positron pair.
		If not, has any theoretical pair production cross-section ever been published for electron-electron collisions?
		To make a proton have enough extra energy to produce an electron-positron pair is fairly easy.
	www.newton.dep.anl.gov /askasci/phy00/phy00454.htm (312 words)

	Event Display Pictures : Muon-Pair Production (SLAC VVC)
		Event Display Pictures : Muon-Pair Production (SLAC VVC)
		An initial electron and positron annihilate and the resulting Z-particle decays producing a muon and an anti-muon.
		Stanford Linear Accelerator Center, Menlo Park, CA Operated by Stanford University for the U.S. Dept. of Energy
	www2.slac.stanford.edu /vvc/theory/eventpix/muonpair.html (218 words)

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