In physics, the W and Z bosons are the elementary particles that mediate the weak force. Their discovery has been heralded as a major success for the Standard Model of particle physics. The W particle is named after the weak nuclear force. The Z particle was semi-humorously given its name because it was said to be the last particle to need discovery. Another explanation is that the Z particle derives its name from the fact that it has zero electric charge. Basic properties Two kinds of W bosons exist with +1 and ?1 elementary units of electric charge; the W^+ is the antiparticle of the W^?. The Z boson (or Z^0) is electrically neutral and is its own antiparticle. All three particles are very short-lived with a mean life of about 3 × 10^?25 seconds. These bosons are heavyweights among the elementary particles. With a mass of 80.4 and 91.2 GeV/c^2