Context [Top]

Name of creator

CERN (Geneva, Switzerland), UA1 Collaboration.

Administrative history

The UA1 project began in 1976; the idea was to detect the communicators of weak interaction (W and Z bosons), which had been postulated but never observed. To achieve this goal, the experiment planned to collide proton beams with antiproton beams in the Super Proton Synchrotron with an energy of 270 GeV. The problem, which Van der Meer solved, was to stock large amounts of antiprotons.

A new type of detector to see the hypothetical bosons. One of the most important and technically advanced items was the large drift chamber, called the central detector. This drift chamber was 6 meters in length and over 2 meters in diameter. The UA1 experiment also had an electromagnetic calorimeter, a hadron calorimeter and a muon detector. The full detector weighed over 2000 tonnes. The results collected by the detector were recorded on magnetic tapes. Carlo Rubbia managed the construction of this large detector.

In summer 1981 the first collision between protons and antiprotons was recorded. The first experiments began in November 1981. At the beginning of 1982 two accidents damaged the UA1 detector, so the experiment was stopped until summer 1982. UA1 and UA2 experiments started again in September 1982 until December 1982, when the accelerators were switched off for two months. During this time data were analysed and physicists were convinced of having discovered the W boson. This was announced in a press conference held on 25 January 1983. The next step was the discovery of Z boson. The experiments on SPS began again on April 1983, and there were soon major results. On 1 June 1983 CERN formally announced the discovery of the Z boson.

The discovery of W and Z bosons ld to a Nobel prize for Carlo Rubbia and Simon Van der Meer: "The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 1984 jointly to Professor Carlo Rubbia, CERN, Geneva, Switzerland and Dr Simon Van der Meer, CERN, Geneva, Switzerland, for their decisive contributions to the large project, which led to the discovery of the field particles W and Z, communicators of weak interaction".

Immediate source of acquisition or transfer

Received from Alan Norton the 30th May 1995.
Received from Lutz Naumann the 30th May 1995.
Received from Guy Maurin the 30th May 1995.
Received from Antoine Lévêque in April 2000.