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W and Z bosons decay to fermion pairs but neither the W nor the Z bosons have sufficient energy to decay into the highest-mass top quark. Neglecting phase space effects and higher order corrections, simple estimates of their branching fractions can be calculated from the coupling constants.
Because exchange of W bosons involves a transfer of electric charge (as well as a transfer of weak isospin, while weak hypercharge is not transferred), it is known as "charged current". By contrast, exchanges of Z bosons involve no transfer of electrical charge, so it is referred to as a "neutral current". In the latter case, the word "current ...
Higgs boson production: Via gluons and top quarks: Via quarks and W or Z bosons: Quad cancellations: One of the many cancellations to the quadratic divergence to squared mass of the Higgs boson which occurs in the MSSM. Primakoff effect: production of neutral pseudoscalar mesons by photons interacting with an atomic nucleus: Delbrück scattering
This table gives the values of the electric charge (the coupling to the photon, referred to in this article as [a]). Also listed are the approximate weak charge (the vector part of the Z boson coupling to fermions), weak isospin (the coupling to the W bosons), weak hypercharge (the coupling to the B boson) and the approximate Z boson coupling factors (and in the "Theoretical" section, below).
These then give rise to the gauge bosons that mediate the electroweak interactions – the three W bosons of weak isospin (W 1, W 2, and W 3), and the B boson of weak hypercharge, respectively, all of which are "initially" massless.
Because the W′ comes from the breaking of an SU(2), it is generically accompanied by a Z′ boson of (almost) the same mass and with couplings related to the W′ couplings. Another model with W′ bosons but without an additional SU(2) factor is the so-called 331 model with β = ± 1 3 . {\displaystyle \;\beta =\pm {\tfrac {1}{\sqrt {3\;}}}~.}
These three composite bosons are the W +, W −, and Z 0 bosons actually observed in the weak interaction. The fourth electroweak gauge boson is the photon (γ) of electromagnetism, which does not couple to any of the Higgs fields and so remains massless. [23] This theory has made a number of predictions, including a prediction of the masses of ...
Elementary bosons responsible for the four fundamental forces of nature are called force particles (gauge bosons). The strong interaction is mediated by the gluon, the weak interaction is mediated by the W and Z bosons, electromagnetism by the photon, and gravity by the graviton, which is still hypothetical.