W and Z bosons#Z bosons

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The Z- boson (symbol ) is a gauge boson and thus an elementary particle. It provides as well as its relative, the W boson, the weak interaction. While the W - boson is electrically charged, the Z boson is neutral. It is responsible for the so-called neutral currents.

These were predicted within the framework of the Unified theory of electroweak interactions in the 1960s by Sheldon Glashow, Abdus Salam and Steven Weinberg ( 1979 received the Nobel Prize for this theory ), and shortly thereafter with the Gargamelle experiment at CERN in the elastic neutrino scattering observed from electron. The direct detection of the Z boson was not until the year 1983, when stood for a reconstruction of the Super Proton Synchrotron at a proton- antiproton collider sufficient focus energy. For the detection of the W and Z bosons, the detectors were built to UA1 UA2 and. Carlo Rubbia and Simon van der Meer received for the 1984 Nobel Prize in Physics.

Similar to the photon and in contrast to the related W bosons Z boson mediates an interaction between the particles, without the particle (or more precisely: flavor ) to change it. While the photon but gives only forces between electrically charged particles interact, the Z boson with the uncharged neutrinos.

An important test reaction for solar neutrinos is the splitting of deuterium:

It is located in a large water tank of heavy water, in which no normal hydrogen, but deuterium nuclei are included. These are split by the energy transfer from solar neutrinos in neutrons and protons, which can then be detected.

Example reactions of the Z boson can also be found under electroweak interactions.

The Z boson decays with about 70 % being preferred in hadrons, further comprising about 10 % in pairs of charged leptons ( e e -, μ μ - or τ τ - ) and with about 20 % in particles in particle collider experiments of can not be detected. Since it is assumed that these undetectable particles are the light neutrinos, allowing the accurate measurement of total and partial decay widths of the Z boson and the determination of the number of generations of light neutrinos. The evaluation of current experiments, this gives a value of 2.92 ± 0.05, which agrees well with the three known neutrino species.

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