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Topic: Cross section (physics)

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In the News (Fri 22 Mar 19)

  Plasma Physics and Astrophysics Research Papers and Proposals
Expressions are derived for the atomic cross sections concerning the resonant scattering, photo-ionization and radiative recombination processes under full consideration of the quantum-mechanical boundary conditions for a resonant oscillator (for both the one-dimensional as well as the two-dimensional case which is relevant for circular polarization and/or magnetic fields).
The charge-exchange cross sections are shown to have a crucial influence upon the ion densities of the minor constituents.
Cross section and energetical width of the excitation band are assumed to be identical with the line profile for resonant scattering of radiation.
www.plasmaphysics.org.uk /research   (6598 words)

  Cross section (physics) - Wikipedia, the free encyclopedia
In nuclear and particle physics, the concept of a cross section is used to express the likelihood of interaction between particles.
A cross section is therefore a measure of the effective surface area seen by the impinging particles, and as such is expressed in units of area.
Thus for slow neutrons absorbed by the (n, gamma) reaction the cross section in some cases is as much as 1,000 barns, while the cross sections for transmutations by gamma-ray absorption are in the neighborhood of 0.001 barns.
en.wikipedia.org /wiki/Cross_section_(physics)   (720 words)

 Cross section - Wikipedia, the free encyclopedia
In geometry, a cross section is the intersection of a 3-dimensional body with a plane; see cross section (geometry).
In differential and algebraic geometry and topology, a cross section is an alternative name for a section of a Fiber bundle or a sheaf.
In physics, a cross section represents the probability of an interaction event between two particles; see cross section (physics).
en.wikipedia.org /wiki/Cross_section   (135 words)

 Physics Encyclopedia Article @ LaunchBase.org   (Site not responding. Last check: 2007-10-20)
Physicists study a wide range of physical phenomena spanning all length scales: from the sub-atomic particles of which all ordinary (i.e., baryonic) matter is made (particle physics) to the behavior of the material Universe as a whole (cosmology).
Physics is sometimes said to be the "fundamental science", because each of the other natural sciences (biology, chemistry, geology, etc.) deals with particular types of material systems that obey the laws of physics.
Condensed matter physics, by most estimates the largest single field of physics, is concerned with how the properties of bulk matter, such as the ordinary solids and liquids we encounter in everyday life, arise from the properties and mutual interactions of the constituent atoms.
www.launchbase.org /encyclopedia/Physics   (4293 words)

The concept of cross section is the crucial key that opens the communication between the real world of experiment and the abstract, idealized world of theoretical models.
The cross section is the probability that an interaction will occur between a projectile particle-say, a proton that has been accelerated in the Tevatron-and a target particle, which could be an antiproton, or perhaps a proton or neutron in a piece of metal foil.
The cross section for large-angle scattering is the fraction of alpha particles that bounce back from the target, divided by the density of nuclei in the target and the target thickness.
www-ed.fnal.gov /painless/htmls/cross.html   (594 words)

 Radar cross section - Wikipedia, the free encyclopedia
High frequency approximations such as geometric optics, Physical Optics, the geometric theory of diffraction, the uniform theory of diffraction and the physical theory of diffraction are used when the wavelength is much shorter than the target feature size.
To calculate the radar cross section of such a stealth body, one would typically do one dimensional reflection calculations to calculate the surface impedance, then two dimensional numerical calculations to calculate the diffraction coefficients of edges and small three dimensional calculations to calculate the diffraction coefficients of corners and points.
The cross section can then be calculated, using the diffraction coefficients, with the physical theory of diffraction or other high frequency method, combined with Physical Optics to include the contributions from illuminated smooth surfaces and Fock calculations to calculate creeping waves circling around any smooth shadowed parts.
en.wikipedia.org /wiki/Radar_Cross_Section   (1570 words)

 1973: Physics - Archive Article - MSN Encarta
Cross references refer to Archive articles of the same year.
If it were possible to designate any single item as the bread and butter of particle physics, it would probably be experiments in which an accelerated high-energy proton is struck against another proton.
The most general piece of information that can be gotten out of such an experiment is the total...
encarta.msn.com /sidebar_1741581810/1973_Physics.html   (149 words)

 Definition of Scattering Cross Section
A cross section depends on the types of particles involved and usually depends on the energy of the particles in the beam.
In general, the cross section is the effective area of the collision region.
This equation reproduces the correct result for the cross section in the classical case where B and T are balls and defines the cross section for the general situation.
www.jupiterscientific.org /sciinfo/crosssection.html   (946 words)

 Lecture 1 Summary
Cross sections in particle physics are measured in [barn]
The cross section covers the physics of the particle reaction whereas the luminosity depends on the properties and the performance of the accelerator.
We have seen that both the cross section and the decay rate depend on the square of a matrix element that describes the underlying process.
www.physics.ohio-state.edu /~klaus/phys780.20/lecture_notes/lecture4_summary.html   (473 words)

 MTSU Department of Physics and Astronomy
For s-process studies the important parameter is the Maxwellian-averaged capture cross sections and with kT=10 keV, the contribution from the overlap of the measured cross section and the Maxwellian weighing function extends well below 1 keV.
However, their value for the cross section is 20% smaller than the previously accepted value and is in disagreement with recent measurements by Theis et al.
Cross sections are also needed for unstable nuclei that occur in the s-process path.
www.mtsu.edu /~physics/carltonGrants.htm   (4316 words)

 ipedia.com: Cross section Article   (Site not responding. Last check: 2007-10-20)
In geometry, a cross section is the intersection of a body in 3-dimensional space with a plane, or of a body in 2-dimensional space with a line, etc. More plainly, when cutting an object into slices o...
In geometry, a cross section is the intersection of a body in 3-dimensional space with a plane, or of a body in 2-dimensional space with a line, etc. More plainly, when cutting an object into slices one gets many parallel cross sections.
A cross section is a common method of depicting the internal arrangement of a 3-dimensional object in two dimensions.
www.ipedia.com /cross_section.html   (512 words)

 Coulomb Collision Cross Section and Coulomb Logarithm
In all corresponding treatments in the literature, the total cross section for Coulomb scattering, as derived over the differential cross section, is obtained as a divergent expression unless an arbitrary cut-off value for the impact parameter (or scattering angle) is introduced (this leads to the well known Coulomb Logarithm factor).
Note that with Eq.(13) a finite expression for the total cross section has been obtained, contrary to the usual but erroneous treatment of the problem where neglection of the additional factor Eq.(6) leads to the well known logarithmic divergence (Coulomb Logarithm) of the total cross section.
The notion of 'infinite-range' potentials must therefore be abandoned, since the effective total cross section (as a physical quantity) always has a finite value independent of macroscopic parameters of the associated plasma.
www.plasmaphysics.org.uk /coulomb.htm   (930 words)

 Neutron Capture and Cross   (Site not responding. Last check: 2007-10-20)
When the capture cross section is less than the geometric cross section, the neutron is less likely to be captured than to make contact.
The cross section for neutrino capture (which is even less likely) would be smaller.
Tim Mooney ======================================================== The concept of a "cross section" is somewhat of a mis-nomer.
www.newton.dep.anl.gov /askasci/phy00/phy00464.htm   (369 words)

 Domain for CMS DBS Use Cases
Physics events are those with actual collisions during the event.
MC can be categorized according to which subset of physics processes it mimics or according to what steps of data analysis it approximates.
A skim is set of data for a particular physics process, where the data is seen as a subset of another dataset.
www.tc.cornell.edu /~ajd27/cms/PhysicsDomain.html   (1237 words)

 Encyclopedia of Laser Physics and Technology - cross sections, laser, emission, absorption cross sections   (Site not responding. Last check: 2007-10-20)
In laser physics, cross sections are used to quantify the likelihood of optical transition events, e.g.
A convenient technique for laser modeling is therefore to use so-called effective cross sections, which are a kind of averages of the cross sections of different sublevel transitions, with weight factors derived from population densities in thermal equilibrium.
For a laser gain medium, the most relevant cross sections are the absorption and emission cross sections at the pump and laser wavelengths.
www.rp-photonics.com /cross_sections.html   (587 words)

 NIST: Electron-Impact Cross Section Database
This is a database primarily of total ionization cross sections of molecules by electron impact.
The cross sections were calculated using the Binary-Encounter-Bethe (BEB) model, which combines the Mott cross section with the high-incident energy behavior of the Bethe cross section.
Electron-impact excitation cross sections are also included for some selected atoms.
www.physics.nist.gov /PhysRefData/Ionization/Xsection.html   (156 words)

 Audition Promenade round Cochlea autour CochlĂ©e oreille ear organ of Corti oreille ear CRIC Montpellier Remy Pujol U254   (Site not responding. Last check: 2007-10-20)
This mid-modiolar section shows the coiling of the cochlear duct (1) which contains endolymph, and the scala vestibuli (2) and scala tympani (3) which contain perilymph.
Within the modiolus, the spiral ganglion (4) and auditory nerve fibres (5) are seen.
Cross section of one single turn of the cochlea
www.iurc.montp.inserm.fr /cric/audition/english/cochlea/cochlea.htm   (280 words)

 Measurement of the WW cross section
To measure the cross section of the WW pair production we have to carefully estimate the background contributions from all possible processes.
The unit of a cross section is the barn (b): 1 b = 10
The theortical calculation for the WW cross section is shown in red as function of center of mass energy of the colliding protons and anti-protons.
www-d0.fnal.gov /Run2Physics/WWW/results/final/EW/E04A/E04A.htm   (1174 words)

 The Nanotechnology Bookstore
He begins by explaining measurement systems and physical scales, and then introduces atoms and molecules, giving both scientific basics and historical perspective, and segueing into the most relevant facts from biochemistry and molecular biology.
A section on "A Genealogy of Nanotechnology" presents the novel (and debatable) perspective that "The companion fields of nanotechnology and artificial-life studies can be usefully thought of as being the inside-out of each other.
A final section on "Research Frontiers" includes brief synopses of recent (circa 1995) work with scanning probe microscopes, nanotubes, biomolecules as motors and computational elements, rational design and directed evolution of molecules, evolution of software and genetic algorithms, self-replication, reversible logic and other computational architectures, and artificial membranes to encapsulate reacting molecules.
www.foresight.org /nano/Bookstore.html   (2518 words)

 SparkNotes: Vector Multiplication: The Cross Product
We saw in the previous section on dot products that the dot product takes two vectors and produces a scalar, making it an example of a scalar product.
In other words, if we take a pair of vectors in the plane and rotate them both by the same angle (imagine, for instance, that the vectors are sitting on a record, and rotate the record), their dot product will remain the same.
Fortunately, as is the case with the dot product, there is a simple geometric formula for computing the cross product of two vectors, if their respective lengths and the angle between them is known.
www.sparknotes.com /physics/vectors/vectormultiplication/section2.rhtml   (1281 words)

 At what rate do electrons flow through any cross section...
At what rate do electrons flow through any cross section...
I submitted it konwing it would be wrong, because it said it wanted section s^-1.
If i'm trying to find what rate electrons flow thorugh any cross section of the heater element, I need to find # of electrons/time, like you said..
www.physicsforums.com /showthread.php?t=94999   (390 words)

 Conventional Fusion FAQ Section 1/11 (Fusion Physics)
The probability that two nuclei fuse is determined by the physics of the collsion, and a property called the "cross section" (see glossary) which (roughly speaking) measures the likelihood of a fusion reaction.
These reactions are also described in Section 2 in the context of their usefulness for energy-producing fusion reactors.
Plasma physics is the area of physics which studies ionized gases and their properties.
www.faqs.org /faqs/fusion-faq/section1-physics   (4301 words)

 Does the ElectroMagnetic Wave have cross-section area !!
Frequently in physics an idealized model is used on real world situations because the results are close enough to measured ones for the intended situation.
You seem to be drifted very much away from "the valid question ahmed osama is asking" the question is not about the depth of penegtration in a metal or its "non-artistic" images in a "finite cross section wire" but if there exist an atomic level radiation cross section of emission.
However, one photon can't have a cross sectional area because it can't have a wave packet simply.
www.edaboard.com /ftopic84703.html   (1049 words)

 Emily's Research Page
The tau neutrino was the last of the fundamental particles predicted by the Standard Model of particle physics whose interaction had not been observed.
Since this was the first time the tau neutrino interaction was observed, the DONuT experiment had the opportunity to make the first measurement of the tau neutrino cross section.
The Standard Model of particle physics predicts lepton universality, which means the tau, muon, and electron neutrinos should behave identically with the exception of kinematic factors.
www.holycross.edu /departments/physics/emaher/research/researchindex.html   (552 words)

 D0 Direct Photon Analysis
Cross Section paper accepted for publication in PRL; hep-ex/9912017, Fermilab-Conf-99/354-E. 1B Cross Section Physics Note Latest Draft (June 1999)
PRL 77 (1996) 5011 "The Isolated Photon Cross Section in the Central and Forward Rapidity Regions in ppbar Collisions at sqrt(s)=1.8 TeV." The Run IA measurement.
Cross Section data from this paper as available from the Durham-RAL database.
www-d0.fnal.gov /~womersle/photon.html   (258 words)

 Radiative Recombination Cross Section for Rydberg States   (Site not responding. Last check: 2007-10-20)
Radiative recombination cross section as a function of electron energy for some (effective) atomic levels and total (normalized corresponding to oxygen at 1200
(the exact wave functions for hydrogen-like atomic systems have been used for the numerical calculations; the absolute value of the curves was normalized so that the cross section for n
=1 was identical with the (measured) value for the photo-ionization cross section; see the Home Page for a detailed discussion of the theory).
www.plasmaphysics.org.uk /research/recrsect.htm   (76 words)

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