mib The Institute for Particle Physics of ETH Zurich (1) has completed the superconducting magnet coil for the CMS detector. The group, working with Felicitas Pauss, ETH Professor of Particle Physics, and Hans Hofer, retired Professor of Experimental High Energy Physics, celebrated this milestone, last week at ETH Hönggerberg.

Particle physics deals with the elementary building blocks of matter and their effect on one another. Basic matter is made up of quarks and leptons which, together with subatomic energy particles, can be arranged in a simple (theoretical) pattern. The accounts, however, do not balance; matter is missing somewhere. To overcome this deficit so-called Higgs particles were added to the theory to act as fillers. The existence of these particles is not proven but there is first evidence: in September 2000 physicists at the European Laboratory for Particle Physics in Geneva (CERN) detected signs of Higgs particles. More data has not emerged but this could change. In four years time, if all goes to plan, the Large Hadron Collider (LHC), a new and more powerful particle accelerator, will take up its work (2). With this installation, physicists will be able to accelerate protons with 14 tera-electronvolts and make them collide with one another. The collided protons are "destroyed" but fragments can be measured, for example, with the Compact Muon Solenoid Detector , which is being built with ETH participation. Felicitas Pauss hopes that Higgs particles will be detected. At least she already knows that they can be detected with about 114 giga-electronvolts.

The tunnel of the particle accelerator LHC is 130 metres underground. In the 27 km-long circular tunnel protons moving in opposite directions are accelerated and made to collide. Detectors, such as Alice, Atlas and CMS register these collisions. Graphics: Cern large

Mid-February 2003: The Compact Muon Solenoid is assembled. The vacuum tank protrudes from the myonen chamber (red). It is in here that the superconducting magnet coil and highly sensitive measuring instruments will be attached to the module. Picture: Maximilien Brice/Cern large

The collided protons are "destroyed" but fragments can be measured, for example, with the Compact Muon Solenoid Detector (3), which is being built with ETH participation. Felicitas Pauss hopes that Higgs particles will be detected. At least she already knows that they can be detected with about 114 giga-electronvolts. But it is not only Higgs particles that ETH scientists are trying to track down. The new particle accelerator and the CMS detector could hold the key to unlocking one of the remaining mysteries of the big bang. Because some questions are still open. Where, for instance, is the greater part of antimatter that "disappeared" when our universe was born, the mass of which is believed to be equal to that of matter? And does a parallel universe exist somewhere, as supersymmetry theory predicts?

Physicists at ETH Hönggerberg must be patient until the first answers begin to arrive. But the first steps towards finding them have been taken. After ten years of research ETH scientists have more or less completed the superconducting magnet coil, destined for the CMS detector. "A technical challenge," says Felicitas Pauss. Because its production was far from easy: the superconducting coil, made of a niobium-titanium alloy, had to be embedded in very pure aluminium. This requirement, in its turn, amplified the difficulties, complicated, as enormous pressure had to be applied to the encasing with a current of 20’000 Ampère and a temperature of minus 269 degrees centigrade. In addition, each of the 20 cables is 2.5 kilometres long. The first stage of the work is finished and the magnet coil must now be attached to each module. ETH physicist Bertrand Blau estimates that this work will take until mid-2004. Researchers, however, must wait until 2007 for the LHC particle accelerator and the CMS detector to be operational.