In weak interactions, W and Z bosons interact with each other, as well as with all quarks and leptons. The Universe would be an impossibly boring place without them. As you know, the beta-minus decay of a nucleus occurs when a neutron turns into a proton, with the emission of an electron and an electron antineutrino. At most, a few MeV of energy are released in this process, corresponding to the difference in mass between the original nucleus and the resultant nucleus.
At the quark level, the explanation is that a down quark, d, with a negative electric charge equal to one-third that of an electron is transformed into an up quark, u, with a positive electric charge equal to two-thirds that of a proton. In accordance with the energy—time uncertainty principle it therefore rapidly decays to produce an electron and an electron antineutrino, setting the energy accounts straight.
In weak interactions, the total number of quarks minus the total number of antiquarks is the same both before and after the interaction. The number of leptons is also conserved. In the example of beta-minus decay, there are no leptons initially present, and after the interaction there is one lepton and one antilepton — a net result of zero again. This is the explanation for why neutrinos and antineutrinos are produced in beta-decays.
If they were not, then the rule of lepton conservation would be violated. Notice also that the production of a charged lepton is always accompanied by the corresponding flavour of neutrino. In all weak interactions:. Check that electric charge is conserved, that the number of quarks minus the number of antiquarks is conserved, and that the number of leptons minus the number of antileptons is conserved.
The electric charge is initially that of an up quark prefix plus of two divided by three times e. Since neutrinos do not have electric charge they cannot self-interact via a photon, which would be the only other option.
In fact, the Z boson is closely related to the photon. You may know that electromagnetic interactions proceed through photons.
Because the photon has no mass, it can travel infinite distances and two electric charges can feel each other even at very large distances. As announced in July of at CERN, scientists have discovered a boson that looks much like the particle predicted by Peter Higgs, among others.
While this boson is not yet confirmed as the Higgs boson predicted to make sense of the electroweak force, the W boson had a large part in its discovery. According to the predictions of the Standard Model , which takes into account electroweak theory and the theory of the Higgs mechanism, the W boson at that mass should point to the Higgs boson at a mass of less than GeV.
W boson: Sunshine and stardust The W boson carries the weak force. Their mass limits the range of the weak force to about 10 metres, and it vanishes altogether beyond the radius of a single proton. Enrico Fermi was the first to put forth a theory of the weak force in , but it was not until the s that Sheldon Glashow, Abdus Salam and Steven Weinberg developed the theory in its present form, when they proposed that the weak and electromagnetic forces are actually different manifestations of one electroweak force.
By emitting an electrically charged W boson, the weak force can cause a particle such as the proton to change its charge by changing the flavour of its quarks. In , Sidney Bludman suggested that there might be another arm of the weak force, the so-called "weak neutral current," mediated by an uncharged partner of the W bosons, which later became known as the Z boson.
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