First physics from LEP

On 13 October, four days after the end of the first physics run of CERN's new LEP electron–positron collider, all auditorium space and every closed-circuit TV vantage point was taken for presentations by the four experiments – Aleph, Delphi, L3 and Opal.

With good performance from the machine, the experiments had amassed between them more than 10,000 Z particles – the electrically neutral carriers of the weak nuclear force – and physicists were eager to learn the first fruits of the world's largest catch of Zs.

The Z had, until earlier this year, been reserved for the big experiments at the proton–antiproton colliders, first at CERN and then at Fermilab. With the advent of physics this year at Stanford's SLC linear electron–positron collider, the Mark II detector also joined the action, supplying the first few hundred examples of Zs produced in electron–positron annihilations. Mark ll's physicists improved on previous measurements of the mass of the particle; they also got an improved limit on the different number of lightweight neutrino types allowed in nature. These results showed that there was very little room left for a fourth neutrino type to complement the three (electron-, muon- and tau-types) known so far.

With the deluge of statistics from LEP, the four experiments could significantly refine the accuracy of the Z-mass measurement. The LEP team was able to calibrate the absolute energy of the machine to 45 MeV, only a few parts in a thousand at the Z mass of 91.1 GeV. This is now the largest uncertainty in the Z mass.

The most significant of the initial wave of LEP results is the removal of the remaining uncertainty in the count of neutrino species, with the chances of a fourth light neutrino now down to less than one in a thousand.

• December 1989 pp18–19 (extract).


LHC building work

On a drawing of CERN's 27 km LEP/LHC tunnel, the civil engineering work needed to accommodate CERN's new LHC accelerator appears minor. However, it is anything but. The total cost of civil engineering will amount to some 50% of the original cost of digging the tunnel (before adjusting for inflation), and due to the amount of work required, contracts are being awarded in three separate packages each valued at around SFr100 million.

Following a market survey of 113 firms in 17 of CERN's member states, calls for tender were sent out in March and April 1997. Decisions to negotiate contracts were then taken by the laboratory's finance committee in November. Package one is for all of the surface buildings and caverns for the ATLAS experiment. It is the only package to require surface building in Switzerland. Following the go-ahead from the Swiss authorities, a joint venture between Austrian, German and Swiss firms has started work.

Package two is for the surface buildings and caverns for the smaller CMS experiment. It will be awarded to an Italian–Spanish consortium and work is expected to start in June. Little civil engineering is required by the ALICE and LHC-B experiments, leaving package three to deal mainly with the clockwise transfer tunnel, the two beam dumps at Point 6, and various other modifications around the ring to accommodate LHC equipment. Package three will be awarded to a Franco–British consortium and work will begin in June.

• May 1998 pp2–3 (extract).


Caught in the Web

The World Wide Web may have taken the Internet by storm, but many people would be surprised to learn that it owes its existence to CERN. Around half of the world's particle physicists come to CERN for their experiments, and the Web is the result of their need to share information quickly and easily on a global scale. Six years after Tim Berners-Lee's inspired idea to marry hypertext to the Internet in 1989, CERN is handing over future Web development to the World Wide Web Consortium, run by the French National Institute for Research in Computer Science and Control, lNRlA, and the Laboratory for Computer Science of the Massachusetts Institute of Technology, MlT, leaving CERN free to concentrate on physics.

The Laboratory marked this transition with a conference designed to give a taste of what the Web can do, while firmly stamping it with the label "Made in CERN". More than 200 European journalists and educationalists came to CERN on 8–9 March for the World Wide Web Days, covered widely in the media.

• June 1995 pp1–4 (extract).


LHC: from start to finish

From the PS to the LHC, the CERN Courier has covered the start-up and inauguration of all of CERN's major particle accelerators. The cover for May 1998 (left) featured Swiss Federal Councillor Kaspar Villiger (right) being greeted by the director-general, Chris Llewellyn Smith (left), on arrival at CERN's heliport on 27 February prior to signing an agreement under which CERN could use land for the LHC.

A decade later, the LHC inauguration was the cover story in December 2008, again with Llewellyn Smith (second right) and Pascal Couchepin, then president of the Swiss confederation.