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Topic: Weak interaction

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In the News (Mon 19 Aug 19)

  Weak isospin - Wikipedia, the free encyclopedia
The weak isospin in theoretical physics parallels the idea of the isospin under the strong interaction, but applied under the weak interaction.
But, in the same way that isospin creates hadron multiplets of particles that are undistinguishable under the strong interaction, all elemental fermions can be grouped in multiplets that behave the same under the weak interaction.
Thus, fundamental fermions are grouped in pairs of particles that behave the same under the weak interaction, and differ from other pairs on their masses (i.e., they belong to different generations of matter).
en.wikipedia.org /wiki/Weak_isospin   (325 words)

 Fundamental Forces
The discovery of the W and Z particles in 1983 was hailed as a confirmation of the theories which connect the weak force to the electromagnetic force in electroweak unification.
This suggests the weak interaction mechanism for the decay of the pion, which is observed to happen by the muon pathway.
The weak interaction in the electron form at left above is responsible for the decay of the neutron and for beta decay in general.
hyperphysics.phy-astr.gsu.edu /hbase/forces/funfor.html   (1170 words)

 Theory: Weak Interactions
Weak interactions involve the exchange or production of W or Z bosons.
Carlo Rubbia and Simon van der Meer were awarded the 1984 Nobel Prize for their development of the facility at CERN which first produced and detected W and Z bosons, and for their leadership of the discovery experiment.
The weak interaction was first recognized in cataloging the types of nuclear radioactive decay chains, as alpha, beta, and gamma.
www2.slac.stanford.edu /vvc/theory/weakinteract.html   (481 words)

 Weak Interaction Encyclopedia Article, Definition, History, Biography   (Site not responding. Last check: 2007-10-07)
The weak nuclear force or weak interaction is one of the four fundamental forces of nature.
The weak interaction enables all lepton and quark particles and antiparticles to interchange energy, mass, electric charge and flavor—effectively to change into each other.
The Standard Model of particle physics describes the electromagnetic force and the weak nuclear force as two different aspects of a single electroweak force, the theory of which was developed around 1968 by Sheldon Glashow, Abdus Salam and Steven Weinberg (more at W and Z bosons).
www.karr.net /search/encyclopedia/Weak_interaction   (577 words)

 MSN Encarta - Search Results - weak interaction
In a weak interaction, or an event that involves the weak force, a decaying particle changes form and emits one of the bosons that mediates the weak...
Weak Nuclear Force: role in the interaction of quarks
In certain circumstances, quarks cannot interact through the strong force, in which case either the weak force or the electromagnetic force takes...
encarta.msn.com /weak+interaction.html   (158 words)

 Feynman diagrams of weak interaction
The basic vertex of purely leptonic weak interactions is shown in Fig.
It is a prototype in which we replace the neutrino and the lepton l by the corresponding allowed neutrino-lepton pairs as shown in Fig.
The needed vertex for a beta+ decay is then received from the standard antielectron weak interaction vertex like shown in Fig.
teachers.web.cern.ch /teachers/archiv/HST2002/Bubblech/feynman.html   (482 words)

 Unification of Forces
The photon, the particle involved in the electromagnetic interaction, along with the W and Z provide the necessary pieces to unify the weak and electromagnetic interactions.
But since the exchange particle for the electromagnetic part is the massless photon and the exchange particles for the weak interaction are the massive W and Z particles, the symmetry was spontaneously broken when the available energy dropped below about 80 GeV and the weak and electromagnetic forces take on a distinctly different look.
This is an apt analogy for the electroweak unification, since the symmetry between the Coulomb force and the weak interaction is certainly not evident at low temperatures.
hyperphysics.phy-astr.gsu.edu /hbase/forces/unify.html   (897 words)

 Examples of the use of Feynman vertices to describe processes
This is a weak decay of the anti-strange quark.
This is a weak decay of the strange quark.
The Feynman diagram illustrates that the reaction is a combination of a quark weak vertex and a weak-lepton vertex.
teachers.web.cern.ch /teachers/archiv/HST2002/feynman/examples.htm   (1005 words)

 The Hadronic Weak Interaction in pp Scattering   (Site not responding. Last check: 2007-10-07)
The weak interaction is remarkable in that it does not exhibit mirror-reflection or `parity' symmetry, in contrast to the other fundamental interactions of nature.
While a successful theory of weaK interactions exists, it is not yet possible to make accurate predictions of how the weak interaction will manifest itself in a system of strongly interacting particles.
The interaction is studied by measuring the intensity of a proton beam that is transmitted through a cryogenic liquid hydrogen target.
www.triumf.ca /E497/e497simple_shelley.html   (361 words)

 The IUCF Weak Interaction Group
NIST (2004)] Again, the idea is to learn about the weak interaction of a neutron with other neutrons and protons, but this time in a system that is simple enough for the results to be interpreted cleanly in terms of the neutron-neutron and neutron-proton weak interaction.
A515, 563 (2003).] This interaction, which has never been measured, is the only remaining interaction of the known forces among the particles of "normal" matter (protons, neutrons, and electrons), which has yet to be determined.
In addition to applications of these neutron polarizers to weak interaction experiments, we are pursuing applications in neutron scattering.
www.iucf.indiana.edu /Experiments/WEAK   (1566 words)

If the weak interaction were a little too weak, then even the dense shock wave would be transparent to neutrinos, and they would flood out throughthe star without getting involved in pushing apart the outer layers of the star.
If, on the other hand, the weak interaction were a little too strong, then the neutrinos would get involved in reacions in the core itself, and owuld never get out to the region where the shock wave was slowing and giving up the ghost.
The weak intereaction has to be just right to allow neutrinos both to escape from the core and to interact with the shock wave.
www.novanotes.com /jan2003/anthro2.htm   (1127 words)

W+, W-, Zo This was later modified when it was discovered that the basic strong interaction is indeed the gluon interaction between the quarks and that nuclear forces mediated by the pi- mesons are merely forms of its outward appearance, a sort of QCD van der Waals force.
Let us consider weak interaction to be the magnetic equivalent of the strong interaction and harmony is restored.
Still, the weak interaction can be brought into a closer relationship with the strong one, closer than with the electromagnetic interaction.
www.geocities.com /CapeCanaveral/Galaxy/7386/chart.html   (331 words)

 The weak interaction   (Site not responding. Last check: 2007-10-07)
Four interactions are known today: the gravitation, the electromagnetism, the strong interaction and the weak interaction.
For the transport of the weak interaction, 3 other bosons are needed: the W+, the W- and the Z. When a radioactive nucleus emits an electron (beta decay), it is in fact a neutron within the nucleus that transforms into a proton by emitting a W- which, soon after, decays into an electron anti-neutrino pair.
Until now, this is the only known interaction where has been observed a violation of parity (P), which is the spatial symetry, and a violation of the symetry between particles and anti-particles (C).
wwwlapp.in2p3.fr /neutrinos/aifaible.html   (382 words)

 Press Release: The 1979 Nobel Prize in Physics
The weak interaction finds practical application in the radioactive elements used in medicine and technology, which are in general beta-radioactive, and in the beta-decay of a carbon isotope into nitrogen, which is the basis for the carbon-14 method for dating of organic archaeological remains.
However, a satisfactory description of the weak interaction between particles at low energy could be given only after the discovery in 1956 that the weak force differs from the other forces in not being reflection symmetric; in other words, the weak force makes a distinction between left and right.
An important consequence of the theory is that the weak interaction is carried by particles having some properties in common - with the photon, which carries the electromagnetic interaction between charged particles.
nobelprize.org /physics/laureates/1979/press.html   (1015 words)

Neutrons and neutrinos interact with electrons and protons by means of the weak nuclear interaction.
This is the interaction that is responsible for radioactive decays of unstable isotopes.
Once the weak interaction have effectively halted, the residual number of neutrons (and neutrinos) is fixed.
astron.berkeley.edu /~mwhite/darkmatter/bbndetails.html   (870 words)

 CERN Courier - ISOLDE tests the Standard Mo - IOP Publishing - article
It is a manifestation of the weak interaction, which acts over distances that are small compared with nuclear dimensions.
That means that the nucleus can be used as a microlaboratory for investigating the weak interaction, thus putting the Standard Model to the test.
The WITCH experiment (Weak Interaction Studies Using an Electromagnetic Ion Trap), which is scheduled to run in 2002, will look for scalar and tensor components of the weak interaction - physics "forbidden" by the Standard Model.
www.cerncourier.com /main/article/41/6/4   (749 words)

 Weak Interaction Rates for Supernova Physics   (Site not responding. Last check: 2007-10-07)
Weak interaction initiates the gravitational collapse of the core of a massive star.
It also determines the mass of the core, strength of the shock wave and plays an important role in the neutronization of the core material and formation of heavy elements at the final stages of supernova explosion.
Weak interaction rates at high temp eratures and densities are calculated for the first time using a microscopic theory for sd-, fp- and fpg-shell nuclei.
flux.aps.org /meetings/YR00/DNP00/abs/S1720013.html   (141 words)

 Comparison of murine and human nectin1 binding to herpes simplex virus glycoprotein D (gD) reveals a weak interaction ...   (Site not responding. Last check: 2007-10-07)
Comparison of murine and human nectin1 binding to herpes simplex virus glycoprotein D (gD) reveals a weak interaction of murine nectin1 to gD and a gD-dependent pathway of entry.
Comparison of murine and human nectin1 binding to herpes simplex virus glycoprotein D (gD) reveals a weak interaction of murine nectin1 to gD and a gD-dependent pathway of entry.Copyright 2001 Academic Press.
We infer that gD represents a weak ligand in the interaction between mNectin1 and virions, whereas it represents a strong and the major ligand for hNectin1.
www.pdg.cnb.uam.es /UniPub/iHOP/gp/8725657.html   (316 words)

 Weak interaction helps locate strange quark in proton structure
During the past two summers the SAMPLE experiment at the MIT-Bates Linear Accelerator Center has shed new light on this question by measuring the proton magnetic moment as seen by the weak interaction, rather than the electromagnetic interaction.
"Using a theoretical estimate for the contribution of the weak interaction axial current, the portion of the magnetic moment due to strange quarks comes out to be significantly positive, contrary to most theoretical models," Beck said.
The SAMPLE experiment is a collaboration between the U. of I., California Institute of Technology, Louisiana Tech University, University of Maryland, Massachusetts Institute of Technology, College of William and Mary, and Virginia Polytechnic Institute and State University.
www.eurekalert.org /pub_releases/2000-02/UoIa-Wihl-0202100.php   (414 words)

 Weak Interaction Rates in Convective Silicon Burning in Massive Stars   (Site not responding. Last check: 2007-10-07)
New calculations of convective silicon burning are presented to study the dependencies on weak interaction rates.
Both 1D hydrostatic models and 2D hydrodynamic models are married to a large nuclear network (160 nuclei) and employ the newly calculated weak interaction rates.
The collective role of iron-peak nuclei as a sink of energy via neutrino losses from the weak interactions is emphasized along with any hydrodynamical effects that play upon the local flavor of the neutrino emission, which regulates the convection.
www.aas.org /publications/baas/v28n4/aas189/abs/S078002.html   (273 words)

 Weak Interaction Rates
Weak Interaction Rates of sd-Shell Nuclei in Stellar Matter Data by T. Oda, M. Hino, K. Muto, M. Takahara and K. Sato, Rate Tables for the Weak Processes of sd-Shell Nuclei in Stellar Matter; Atomic Data and Nuclear Data Tables, 56, 231-403 (1994).
Abstract The weak interaction rates in stellar matter are calculated for the sd-shell nuclei in the full-shell model configurations using the effective interaction of Wildenthal, taking into account the recent extensive compilations of experimental energy levels and Gamow-Teller beta decay rates.
The weak rates are tabulated at the same grid points of density and temperature as those of FFN, for the ranges 10 < rho*Y
ie.lbl.gov /astro/oda.html   (305 words)

 Weak Interactions
The effective strength of the weak interaction at low energies thus depends both on the coupling of the W to fermions, g, and upon its mass.
In the 1960's, Glashow, Salam and Weinberg proposed the unification of the electromagnetic and weak interactions as a single gauge theory with a common coupling constant.
Supplementary material on the weak interaction, mainly of a popular or non-technical nature, can be obtained from a number of sources.
www.shef.ac.uk /physics/teaching/phy304/weak.html   (737 words)

 The Neutron as a Fundamental Physics Laboratory   (Site not responding. Last check: 2007-10-07)
Two classes of experiments are being performed at the NIST Center for Neutron Research to characterize the weak interaction through measurements of parity violation and neutron beta decay.
The strong interaction alters the hadronic weak interaction so it is not simply related to the elementary weak interaction.
Neutron beta decay probes the weak interaction at the quark level.
www.nist.gov /sigmaxi/Posters00/Abst/Huffman-abst.html   (172 words)

 7 - Combining the electromagnetic and weak Interaction
For a long time, electromagnetic and weak interactions were thought to be distinct, because their strength, at the low energies normally encountered in daily life, is very different.
The first reaction is electromagnetic (in the quark picture it is electromagnetic elastic electron-quark scattering); the second reaction happens through the weak interaction, as signaled by the outgoing neutrino (in the quark picture the reaction is eq --> Neutrino q).
Both reactions are very similar, expect that the first one occurs via the electromagnetic interaction and the second one via the weak interaction.
www.desy.de /f/hera/engl/chap7.html   (340 words)

 ILL2003 scientific highlights nuclear and particle physics
The importance to measure the weak neutral constant for the nucleonnucleon interaction is evident.
Its value should significantly depend on the vacuum average value of the energy density of the quark condensate in a nucleus, which is of fundamental importance in nuclear physics and in quantum chromodynamics.
Even if the weak neutral current would not exist in the nucleon-nucleon interaction, some non-zero values of the P-odd asymmetry coefficients would be measured at the sensitivity level corresponding to the well-established weak charged currents.
www.ill.fr /AR-03/site/02_scientific/027_nuclear/02_nuclear_05.htm   (844 words)

 weak interactions on Encyclopedia.com   (Site not responding. Last check: 2007-10-07)
Weak interactions are one of four fundamental interactions in nature, the others being gravitation, electromagnetism, and the strong interactions.
Ternary miscibility in blends of three polymers with balanced binary interactions.
The adult attachment interview and observed couple interaction: implications for an intergenerational perspective on couple therapy.
www.encyclopedia.com /html/w1/weakinte.asp   (356 words)

 Weak nuclear force
The weak nuclear force affects all leptons and quarks.
Although the weak nuclear force used to be described by Fermi's theory of a contact four-fermion interaction, today we know that it is mediated by the W and Z bosons.
They were awarded the 1979 Nobel prize in physics for their work.
www.sciencedaily.com /encyclopedia/weak_nuclear_force   (409 words)

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