In a 17-mile tunnel deep beneath the Earth, the search for the God particle

krsna · February 3, 2005

David Adam, science correspondent

Thursday February 3, 2005

The Guardian

The journey down in the lift lasts barely a minute, but is the closest thing on Earth to travelling into another dimension. At the bottom of the shaft is a well lit tunnel that stretches as far as the eye can see, until its barely perceptible curve takes it around a distant corner. This is no ordinary tunnel. It carries no trains or gas pipes and is built in a perfect circle, running for 17 miles about 100 metres below the western suburbs of Geneva, squeezed between the lake on one side and the imposing Jura mountains on the other.

The citizens of Geneva have lived with the tunnel for decades. The citizens of Britain are now spending more than £1m a week to turn it into one of world's biggest and most powerful science experiments.

The only traffic passing through this tunnel when it opens for business will be high energy beams of subatomic particles. By smashing the particles together, scientists want to recreate conditions found in the earliest moments of the universe, billionths of a second after the Big Bang. By peering at what emerges, they hope to better understand the 14bn years that followed.

Professor Ken Peach, a physicist at the Rutherford Appleton Laboratory near Oxford, said: "We have a description of what goes on in the universe but what we don't have is an explanation. A description says this is how things appear, an explanation says this is how things have to be."

This is the shadowy domain of particle physics and the giant experiment taking shape in the tunnel is called the Large Hadron Collider. It is the brainchild of physicists at Cern, the pan-European physics laboratory that celebrated its 50th anniversary last year and created the world wide web, but is best known in some circles for inventing technology used in a plot to blow up the Vatican in the Dan Brown bestseller Angels and Demons.

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Britain's annual membership of Cern costs £76m. Across Europe the lab soaks up more than £350m each year, about 90% of which is currently put into building the Large Hadron Collider, the price tag for which stands at about £1.3bn.

The collider was conceived in the 1980s and serious work to design and build it began in the late 1990s. Progress has been slower than expected - unearthing a Roman villa during excavations was one of the more colourful delays - but the scientists say they are nearing the home straight, which is why the Guardian was granted rare access to the underground facility this week.

When completed, the currently empty tunnel will house two parallel tubes. One will carry high energy particles called protons, accelerated to near the speed of light. The other will carry the same, but in the opposite direction. At several points around the ring, the beams will cross and the energy of the resulting collisions will tear the protons apart, liberating a spray of smaller particles.

Press some physicists enough and they invoke the possible discovery of new, unidentified sources of energy as justification for the colossal investment. But the new collider is more about naked scientific curiosity.

It is also about Nobel prizes. The collisions will release energy levels never before witnessed on Earth and could produce one of the most sought after prizes of modern physics: the Higgs boson, otherwise known as the God particle.

"If the Higgs particle is there then we will find it," said Professor Jim Virdee, a particle physics expert at Imperial College London, who works on the project.

Physicists are desperate to find the Higgs particle because it could plug a hole in a theory that is both their greatest triumph and their biggest headache.

Called the standard model, the theory has been pieced together over the last 50 years to explain how the soup of subatomic particles interact to make the universe tick. But the standard model is showing its age and, as physicists devise bigger and better experiments to test its theoretical predictions, they discover more and more anomalies.

One of the biggest problems is the discovery that even the tiniest, most fleeting particles have some mass - the standard model assumes that they don't.

The Higgs particle offers a way out because physicists think it somehow interacts with all other forms of matter to give them mass. Heavier objects merely interact more.

Prof Virdee said: "We are at a point where the theoretical physicists do not know what direction to take. Nature is a lot smarter than our theorists, so they're waiting for the results of our experiments to decide."

The "experiments" weigh thousands of tons and are the size of ships. Each must detect and analyse the spray of particles given off from each collision, so will be housed in giant underground caverns dug out around the points where the beam lines cross.

The cavern for one experiment, called the CMS, was officially opened this week. It measures 53 metres long, is 24 metres high and 27 metres wide - the result of 35,000 lorryloads of soil and rock being carried away. It is painted white and has a huge hole in the roof, which stretches up to the surface. The giant detector is being assembled on the surface and, when ready, will be lowered into position using a crane borrowed from a German shipyard.

If all goes well the beam lines and the detectors will be finished in time to turn the collider on in late 2007, a deadline set for political as much as scientific reasons. As one project scientist puts it: "One way or another this thing must have collisions in 2007, even if it's on December 31."

Collision course

· Dozens of countries have supplied expertise and parts - the brass in one detector comes from artillery shells salvaged from Russian warships of second world war vintage

· The combined strands of the superconducting electrical cable used in the collider tunnel would stretch round the equator 6.8 times

· The magnets used to steer the particles around the ring will be chilled to about 300C below room temperature, colder than outer space

· The detectors will analyse up to 800m collisions every second - data equivalent to 10,000 Encyclopedia Britannica

· The vacuum pipes to carry the particle beams are checked for leaks so minute it would take 10,000 years to make a car tyre go flat