Simon van der Meers technology of stochastic cooling, the Antiproton Accumulator was also built. The collider started running in 1981 and, in early 1983, an international team of more than 100 physicists headed by Rubbia and known as the UA1 Collaboration, detected the intermediate vector bosons, the W and Z bosons, which had become a cornerstone of modern theories of elementary particle physics long before this direct observation. They carry the weak force that causes radioactive decay in the atomic nucleus and controls the combustion of the Sun, just as photons, massless particles of light, carry the electromagnetic force which causes most physical and biochemical reactions. The weak force also plays a fundamental role in the nucleosynthesis of the elements, as studied in theories of stars evolution. These particles have a mass almost 100 times greater than the proton. In 1984 Carlo Rubbia and Simon van der Meer were awarded the Nobel Prize "for their decisive contributions to the large project, which led to the discovery of the field particles W and Z, communicators of weak interaction". To achieve energies high enough to create these particles, Rubbia, together with David Cline and Peter McIntyre, proposed a radically new particle accelerator design. They proposed to use a beam of protons and a beam of antiprotons, their antimatter twins, counter rotating in the vacuum pipe of the accelerator and colliding head-on. The idea of creating particles by colliding beams of more "ordinary" particles was not new: electron-positron and proton-proton colliders were already in use. However, by the late 1970s / early 1980s those could not approach the needed energies in the centre of mass to explore the W/Z region predicted by theory. At those energies, protons colliding with anti-protons were the best candidates, but how to obtain sufficiently intense (and well-collimated) beams of anti-protons, which are normally produced impinging a beam of protons on a fixed target? Van den Meer had in the meantime developed the concept of "stochastic cooling", in which particles, like anti-protons could be kept in a circular array, and their beam divergence reduced progressively by sending signals to bending magnets downstream. Since decreasing the divergence of the beam meant to reduce transverse velocity or energy components, the suggestive term "stochastic cooling" was given to the scheme. The scheme could then be used to "cool" (to collimate) the anti-protons, which could thus be forced into a well-focused beam, suitable