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Rubrik: Science Life

ETH Zurich particle physics at CERN
Hopefully on a collision course

Published: 05.04.2007 06:00
Modified: 04.04.2007 18:17
The Compact Muon Solenoid (CMS), one of the world’s biggest particle detectors, is halfway through installation at the CERN European Particle Physics Laboratory in Geneva. Its magnet has passed the first test. This was celebrated on 22 March 2007 with more than 200 invited guests and journalists from all over the world. The possibility that ETH Zurich researchers will soon be able to study phenomena of the kind that occurred shortly after the origin of the universe is coming within reach.

Gabrielle Attinger

The workshop building simply called Point 5 outside the little French village of Cessy looks unspectacular: a tall, anonymous and almost windowless corrugated iron block stands here in the middle of a field. Only the words “heavy lifting” appear on a sign on the stirrup-shaped red crane above the building. This very modest description belies what is happening inside the building: the crane is used to lower sections of one of the biggest and heaviest particle detectors ever built into the experimental cavern 100 metres below the ground surface. The biggest segment, the centre section 16 metres high with magnets 13 metres long, weighs approx. 2000 tons, as much as five jumbo jets together.

Guided tour with experts

This section was lowered down into the cavern in late February in an operation lasting ten hours. Then, in the week beginning 19 March 2007, the CERN researchers invited scientists, politicians and the media from the world over to visit and view the construction of the detector in the cavern. Felicitas Pauss, ETH Zurich Professor of Particle Physics and Vice Chair of the Collaboration Board, welcomed the guests in the high assembly building. A speech was given by Professor Tejinder Virdee, spokesman for the CMS experiment, followed by Robert Aymar, General Director of CERN. Small groups of guests were then led by CERN researchers into the underground part of the installation. Günther Dissertori, ETH Zurich Professor for Particle Physics and Project Manager of the detector control system at CMS, together with ETH Zurich staff members Francesca Nessi and Gerard Faber, acted as guides for the Swiss visitors, who included ETH Zurich Vice-president Dimos Poulikakos and ETH Zurich Professor Hans Ruedi Ott. A lift takes you down into a service cavern from where a narrow corridor leads into the big cavern. The two cavities are separated by seven metres of concrete. Dissertori explains that “it ensures one can still work in the service cavern once the CMS is operating.” However, the gigantic hall is still only half full. This reveals particularly well the almost incredible magnitude of the project. Tons of silver, red and blue coated metal enclose the drum in which the superconducting magnet is installed. The individual components are connected together by an enormous collection of blue cables. The 100 metre shaft through which the individual sections are lowered into the cavern can be seen roughly in the middle of the hall. This is precision work: only 20 centimetres of leeway remained between the shaft wall and the CMS element as the large centre section was being lowered down.

Research with Einstein

The last segment is to arrive in the underground cavern in the summer of 2007. The CMS is expected to be commissioned in late 2007. The particle accelerator will also be complete by then. The Large Hadron Collider (LHC) is being built in a tunnel 27 kilometres long. This is the biggest installation of its kind in the world and previously housed the Large Electron-Positron Collider (LEP), which began operations in 1989 and was decommissioned in 2000. Protons will be accelerated to more than 99.9 percent of the speed of light in the LHC. These particles will be made to collide in the centre of the CMS. This involves converting energy into matter according to Einstein’s equation E = mc2: energy equals mass times the speed of light squared. This matter in the form of new particles will be measured and studied. The magnet with its field strength of four Tesla – corresponding to one hundred thousand times the earth’s magnetic field – will deflect each of the electrically charged particles into circular orbits from which ultimately their momentum can be determined. The plan is to find answers to questions such as what are the smallest component parts of matter, what forces act between them and whether hitherto undiscovered particles and interactions exist.

The giant’s heart: the centre segment of the CMS with its magnets is installed in the experimental cavern

ETH Zurich group in the assembly hall: (l. to r.) Lisa and Dimos Poulikakos, Felicitas Pauss, Günther Dissertori, Paul Burkhard (SNF), Hans Ruedi Ott (Photos: Christian Haller)

„Felicitas Pauss explains that “with the CMS we are in a position to study the conditions in the first moments after the Big Bang.” Moments in this context means one hundredth of a billionth of a second. The CMS will also enable the CERN researchers to create miniature big bangs. According to Pauss, the knowledge that this will yield will not only explain the Universe’s past but will also, in collaboration with astrophysicists and cosmologists, enable predictions about its future development.

The search for the Higgs Boson

A total of more than 2000 researchers from 155 institutes in 37 countries are working on the CMS project. Felicitas Pauss is aware that “It is not always easy to achieve a situation where 2000 people are pulling in the same direction.” Nevertheless she is still convinced that the next few years will be the most exciting in this field of research. However, she is unwilling to predict what new knowledge will be the first outcome. She thinks “We might possibly discover something quite different from what we expect on the basis of current theories.“ One of the big questions that the CMS could answer is the existence of the Higgs Boson. Scientists assume that space is filled with a Higgs field and that particles obtain their mass in this field. Particles that interact strongly with the field become heavy and the others remain light. The Higgs Boson is supposed to be responsible for this. Proof of the existence of this particle has not been possible up to the present. However, if it exists, it is likely to be discovered with the new facility. In this connection, Felicitas Pauss explains that “CMS will record such an incredibly large amount of data that we will be able to detect even extremely improbable phenomena.”

Protecting the landscape

CMS is one of a total of four particle detectors that will record data at the LHC. As a whole the research with the LHC is the biggest fundamental scientific research project ever undertaken – and is predicted to change our view of the universe fundamentally. In the meantime the view enjoyed by the local residents at Point 5 will change as soon as the last segment of the CMS has arrived in the experimental cavern. The height of the corrugated iron building will then be considerably reduced. Günther Dissertori says “That was a promise given to the neighbouring residents before building started.” With justification: although the building is unspectacular, it is much too huge in this rural setting.

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