Search results
Results from the WOW.Com Content Network
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
Additionally, we know experimentally that the W and Z bosons are massive, but a boson mass term contains the combination e.g. A μ A μ, which clearly depends on the choice of gauge. Therefore, none of the standard model fermions or bosons can "begin" with mass, but must acquire it by some other mechanism.
W particles have electric charge – there are both positive and negative W particles – however the Z boson is also an exchange particle for the weak force but does not have any electrical charge. Exchange of a Z boson transfers momentum , spin , and energy , but leaves the interacting particles' quantum numbers unaffected – charge, flavor ...
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).
The value of θ w varies as a function of the momentum transfer, ∆q, at which it is measured. This variation, or 'running', is a key prediction of the electroweak theory. The most precise measurements have been carried out in electron–positron collider experiments at a value of ∆q = 91.2 GeV/c, corresponding to the mass of the Z 0 boson, m Z.
In particle physics, W′ and Z′ bosons (or W-prime and Z-prime bosons) refer to hypothetical gauge bosons that arise from extensions of the electroweak symmetry of the Standard Model. They are named in analogy with the Standard Model W and Z bosons .