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Concept
Bosons W et Z
Résumé
In particle physics, the W and Z bosons are vector bosons that are together known as the weak bosons or more generally as the intermediate vector bosons. These elementary particles mediate the weak interaction; the respective symbols are _W boson+, _W boson-, and _Z boson0. The _W boson+- bosons have either a positive or negative electric charge of 1 elementary charge and are each other's antiparticles. The _Z boson0 boson is electrically neutral and is its own antiparticle. The three particles each have a spin of 1. The _W boson+- bosons have a magnetic moment, but the _Z boson0 has none. All three of these particles are very short-lived, with a half-life of about 3e-25s. Their experimental discovery was pivotal in establishing what is now called the Standard Model of particle physics.
The _W boson bosons are named after the weak force. The physicist Steven Weinberg named the additional particle the "_Z boson particle", and later gave the explanation that it was the last additional particle needed by the model. The _W boson bosons had already been named, and the _Z boson bosons were named for having zero electric charge.
The two _W boson bosons are verified mediators of neutrino absorption and emission. During these processes, the _W boson+- boson charge induces electron or positron emission or absorption, thus causing nuclear transmutation.
The _Z boson boson mediates the transfer of momentum, spin and energy when neutrinos scatter elastically from matter (a process which conserves charge). Such behavior is almost as common as inelastic neutrino interactions and may be observed in bubble chambers upon irradiation with neutrino beams. The _Z boson boson is not involved in the absorption or emission of electrons or positrons. Whenever an electron is observed as a new free particle, suddenly moving with kinetic energy, it is inferred to be a result of a neutrino interacting with the electron (with the momentum transfer via the Z boson) since this behavior happens more often when the neutrino beam is present.
Source officielle
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