Large hadron collider restarted for new search

Inside the beam tunnel of the large hadron collider, where scientists hope the secrets of the universe can be unlocked. Picture: PA

Two beams of particles travelling just below the speed of light were sent flying in opposite directions through the LHC’s 16.7 miles of circular underground tunnels straddling the Swiss-French border.

Amid scenes of jubilation in the LHC control room, Professor Rolf Heuer, director-general of Cern, the European Organisation for Nuclear Research, said: “Congratulations. Thank you very much, everyone . . . now the hard work starts.”

Currently, the £3.74 billion machine is running at a low “injection” energy of 450 giga-electron volts (GeV). In June, the energy will be ramped up to a record-breaking 13 tera-electron volts (TeV) and experiments probing the fundamental building blocks of the universe can begin.

Two years ago, the LHC team, which includes a number of British physicists, astounded the world with the discovery of the Higgs boson, an elementary particle that gives other particles mass. Its existence was originally predicted by Nobel laureate Professor Peter Higgs, of Edinburgh University.

Now the scientists have their sights set on an even more exotic trophy – dark matter, the invisible, undetectable material that makes up 84 per cent of matter in the universe and binds galaxies together, yet whose nature is unknown.

With a beam energy of 13 TeV – almost twice that which produced the Higgs boson – it is conceivable that the LHC will capture dark matter, marking a leap forward in our understanding of the universe.

A technical hitch delayed the restart of the LHC after a two-year refit and upgrade. An electrical short circuit prompted fears operations could be put back months. However, engineers quickly located the problem – a small piece of metal debris – and removed it.

As tension built during the final minutes before the restart, Frederick Bordry, Cern’s director for accelerators and technology, handed out Easter eggs to staff.

Protons, the “hearts” of atoms, travel round the LHC at just three metres per second below the speed of light. The protons will be smashed together in four giant detectors located around the beam ring, creating new particles and hopefully opening up a new era in physics.

The search for dark matter involves stepping outside the “standard model”, the all-encompassing theory that describes particles and forces of nature that has stood firm for 50 years.

A “new physics” called supersymmetry predicts every known particle has a more massive partner – and these elusive supersymmetry particles might be the source of dark matter.

Professor Jonathan Butterworth, from University College London, a member of the detector team, said: “It all seemed to go very well this morning.

“We’ll all be watching very excitedly to see what develops over the next few weeks. The LHC’s operating again for the first time in two years and that’s a really important milestone in physics.

“You can think of the LHC as the world’s greatest microscope looking into the heart of matter. At this higher energy level, we don’t know what we’ll see – no-one has looked there before.”