Here under the rolling hills on the French-Swiss border near Geneva, the biggest machine ever built is preparing for a new assault on its elusive quarry. Because it is now make-or-break time for the scientists at Cern, Europe’s nuclear research laboratory, as their titanic Large Hadron Collider (LHC), the most powerful atom smasher in the world, gears up for a frantic rush to corner the elusive Higgs boson, better (if inaccurately) known as the God Particle.
Cern made a tentative announcement last year that it had found “hints” of the Higgs; in the next six months, it will either pin down the elusive particle or force physicists back to the drawing board. The LHC has been repaired and fettled over the winter, and is this week completing a series of test firings before starting high-energy collisions next week.
For almost half a century the particle, whose existence was first predicted by the British physicist Peter Higgs in 1964, has escaped detection – the tools at our disposal were simply not powerful enough to smoke it out. But in the ring of tunnels and caverns buried deep below the Geneva suburbs, engineers are readying their machine for a last, turbo-charged offensive.
Physicists believe not only that the Higgs is there, but that its properties fall between certain parameters. If it turns out not to be there, or to have wildly different properties to what the theories say, the equations will have to be torn up – a prospect that fills physicists with dread and nervous anticipation in equal measure.
With a major overhaul of the LHC due this year, which will see the £6 billion machine shut down for 18 months, the atmosphere at Cern is intense. Rolf-Dieter Heuer, the director-general, has instructed his scientists to confirm or rule out the existence of a Higgs boson (or more precisely a Higgs with the mass predicted by science) before the autumn.
The challenge has been accepted with such gusto that Sergio Bertolucci, Cern’s ebullient, motorbike-mad chief scientist, has told the teams analysing the data from the LHC collisions that he is not interested in painstakingly combining their data (as usually happens) and ordered each to find a cast-iron result on the strength of their measurements alone.
To give their physicists a fighting chance, engineers agreed last month to increase the power of the LHC for the duration of 2012 from seven teraelectronvolts (TeV) of energy to eight, giving each microscopic beam the energy of a Eurostar train travelling at full speed.
One way or the other, Prof Heuer says, 2012 will be the year the Higgs nut is finally cracked. “We plan to have around four times as many statistics this year, and that should settle the question of the standard-model Higgs by the end of the summer. We will have an answer to the Shakespeare question: to be or not to be.”
The Higgs is the embodiment of an ether-like field that, according to the “Standard Model” of physics, endows all other particles with their mass and is a major missing piece in the physics jigsaw puzzle. Without the Higgs mechanism a major part of the Standard Model, a series of equations that describe how the basic particles and forces interact, will be incomplete.
Exploring the physics of the impossibly small requires some gargantuan engineering. From the cathedral-sized chambers where the enormous Atlas and CMS detectors – the two biggest “stations” on the LHC ring – are housed, the sense of urgency among engineers putting the final touches to their eye-wateringly expensive equipment is palpable.
The optimism is reassuringly upbeat, because it is fair to say the LHC did not get off to the most auspicious start. The 17-mile underground ring, through which beams of particles thinner than a human hair are fired in opposing directions, took 10 years to construct and twice as long to design.
But shortly after being launched amid great fanfare in 2008, the machine was brought to a halt by a power cut when a pigeon dropped a piece of bread onto an electrical component.
Days later an electrical fault caused a magnet to fail, sparking a gas leak inside the tube which knocked the entire apparatus out of service for a whole year.
Since it was restarted in 2009 two years’ worth of collisions have brought us closer than ever to finding the truth about the Higgs, but have only uncovered tantalising hints of the particle itself.
Now there is a growing sense that the search may at last be coming to an end – a belief strengthened by the final analysis of data from the American Tevatron, the now-defunct forerunner of the LHC, which found strikingly similar “blips” in its results – terabytes of statistical data generated by the debris resulting from particle collisions.
Cern knows that public – and political – expectation is mounting that a “Higgs result”, which will probably mean Nobel Prizes all round, is needed soon. The LHC costs pounds 690 million a year to run and in a cash-strapped Europe, esoteric research like this is always vulnerable to budget cuts.
But the engineers are also thinking ahead to a new phase in the life of the LHC – when the machine can be ramped up to full power and perhaps open up a new window of post-Higgs, super-high-energy physics. The machine will enter a longer period of hibernation at the end of 2012 for its final upgrade. The LHC is designed to handle 14TeV of energy, but before turning it up to full power, engineers must pull the massive detectors apart and test and repair 10,000 connections along the entire length of the accelerator to make sure they will not buckle under the strain.
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