Carlo Rubbia, 1934–, Italian physicist, Ph.D. Univ. of Pisa, 1957. A professor of physics at the Univ. of Rome and later at Harvard, Rubbia did his most important work with Simon van der Meer at CERN. The pair discovered the W and Z particles, which convey the weak force, one of nature's four fundamental forces (see weak interactions). For their discovery, the pair was awarded the 1984 Nobel Prize in Physics. Rubbia also led a research team that produced theoretical evidence for a sixth quark, called "top" (see elementary particles).