Z particle

Electrically neutral carrier of the weak force and the neutral partner of the electrically charged W particle. It is nearly 100 times more massive than the proton and has a lifetime of only about 10²⁵ second. Z particles were first observed in 1983 by Carlo Rubbia and Simon van der Meer at CERN. Further studies have shown a natural variation in mass that is related to the particle's lifetime through the uncertainty principle. Measurements show that when Z particles decay to neutrino-antineutrino pairs (see pair production), they produce only three types of lightweight neutrino, indicating that there are only three sets each of leptons and quarks.