Beams are back at the LHC

The first beams of 2012 at the LHC. (Courtesy: CERN)

By Hamish Johnston

Just before midnight last night the first proton beams of 2012 were circulated in the Large Hadron Collider (LHC) at CERN in Geneva. Above is a screenshot from the LHC Dashboard showing both clockwise and anticlockwise beams circulating in the LHC for much of today.

It looks as if the beam energy is still fairly low at 0.45 TeV – but the plan for this year is to run both beams at 4 TeV for a collision energy of 8 TeV. Last year, the collider ran at 7 TeV and may have caught the first glimpses of the Higgs boson. By running at a higher energy, LHC physicists hope that it will become clearer whether the Higgs is indeed emerging from collision data with a mass of about 125 GeV/c².

Running at 8 TeV could also help physicists find evidence for the theory of supersymmetry (or SUSY). SUSY is an attractive route beyond the Standard Model because it offers solutions to some of the big questions in particle physics. Many physicists hope that the LHC will confirm SUSY’s central prediction: that for each of the Standard Model particles there exists a heavier sparticle sibling. But, so far, no evidence for SUSY has emerged from the LHC.

However, running at a slightly higher energy does not come without risks. Larger currents must flow through the LHC’s superconducting magnets and we know that in the past there was a problem with the electrical connectors between magnets. In 2008 the LHC failed spectacularly when one of these connectors overheated; and the remote chance of a repeat of this costly disaster must be weighing heavily on the minds of some at CERN.