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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 (seepair production), they produce only three types of lightweight neutrino, indicating that there are only three sets each of leptons and quarks.
This entry comes from Encyclopædia Britannica Concise. For the full entry on Z particle, visit Britannica.com.