FIRST HIGH-ENERGY COLLISIONS CARRIED OUT IN GENEVA
INSPIRATIONAL, 5 Apr 2010
The first high-energy collisions between particle beams have taken place at the Large Hadron Collider, ending more than a year of frustration for scientists in Geneva.
Collisions occurred just after noon BST, five hours after scheduled, but well within the time frame expected by scientists at the European Centre for Nuclear Research (CERN).
"This is a major breakthrough. We are going where nobody has been before. We have opened a new territory for physics,” said Oliver Buchmueller, one of the key figures on the project.
The atomic particles smashed together in head-on collisions, with each beam having an energy of 3.5 trillion electron volts, three times the previous record. By creating ultra-high energy collisions, scientists are mimicking the conditions moments after the Big Bang.
Scientists hope that the LHC will eventually find evidence for the existence of the Higgs boson, a particle that theoretically gives matter mass, but which has never been detected experimentally.
"With these record-shattering collision energies, the LHC experiments are propelled into a vast region to explore, and the hunt begins for dark matter, new forces, new dimensions and the Higgs boson," said Fabiola Gianotti, a spokesperson for Atlas, one of the four particle detector projects running in conjunction with the colider.
Success brought an outpouring of relief from scientists who have guided the project.
"It’s a great day to be a particle physicist," said Professor Rolf Heuer, the director-general of CERN. "A lot of people have waited a long time for this moment, but their patience and dedication is starting to pay dividends."
"This is the moment we have been waiting and preparing for," said Jürgen Schukraft, spokesperson for the Alice detector team.
"We’re very much looking forward to the results from proton collisions, and later this year from lead-ion collisions, to give us new insights into the nature of the strong interaction and the evolution of matter in the early Universe."
Guido Tonelli, spokesman for the CMS detector team, said that data were already flowing in.
"We’ve all been impressed with the way the LHC has performed so far, and it’s particularly gratifying to see how well our particle detectors are working while our physics teams worldwide are already analysing data," Mr Tonelli said.
"We’ll address soon some of the major puzzles of modern physics like the origin of mass, the grand unification of forces and the presence of abundant dark matter in the Universe. I expect very exciting times in front of us."
CERN will run the collider for 18 to 24 months with the objective of delivering enough data to make significant advances across a wide area of physics.
When they have "rediscovered" the known Standard Model particles, a necessary precursor to looking for new physics, the collider teams will start searching for the Higgs boson.
"Over 2,000 graduate students are eagerly awaiting data from the LHC experiments," Professor Heuer said. "They’re a privileged bunch, set to produce the first theses at the new high-energy frontier."
The day started with technical problems as, after a trouble-free overnight test run, first a small power supply glitch and then an over-sensitive magnet safety system left the physicists in suspense for a little longer.
On both occasion the energy of the magnets within the LHC had to be slowly ramped back down to a level at which beams of protons could be re-injected.
Professor Heuer said the technical problems were minor. “The last time CERN switched on a major new research machine, the Large Electron Positron collider, LEP, in 1989 it took three days from the first attempt to collide to the first recorded collisions.
"Such things happen when you have 2,000 magnets and 10,000 other types of device and God knows what else. Such glitches are absolutely normal. I would never have dreamt to have collisions on the first attempt.”
For CERN scientists, the first high-energy collisions mark the end of a frustrating period when they were forced to make do with computer simulations of particle collisions rather than actual data, following a major breakdown of the machine in September 2008.
Nine days after it was switched on, a connection between two magnets failed, tearing a hole in the collider and causing a huge leak of the liquid helium that cools its superconducting magnets.
Engineers took more than a year to investigate and repair the fault, check the rest of the accelerator for similar problems, replace faulty magnets and install new safety devices to prevent a repeat.
The second glitch was caused by a false alert in these additional safety systems, raising questions about whether they were over-sensitive.
Professor Heuer said that a “better safe than sorry” approach was crucial. “We should not make it less sensitive. We have learnt our lesson from September 2008,” he said.
Dr Christophe Delaeve, a physicist working at one of the sites at which collisions are expected, said he had been working continuously since 10am on Monday. “It’s a really exciting moment," he said.
Many other researchers arrived as early as 3am and some were taking naps at their desks while the glitches were addressed.
Physicists from around the world watched the developments at the LHC live on the Cern website, while live weblinks to Fermilab in Chicago, Florida State University, Tehran and Zurich were beamed into the LHC control rooms.
The collisions were expected to take place simultaneously in the detectors of all four experiments: CMS, Alice, Atlas and LHCb.
The two proton beams began circulating at high energy ten days ago in opposite directions around the 17-mile (27km) tunnel under the Swiss-French border at Geneva.
The beams were pushed to 3.5 trillion electron volts in recent days, the highest energy achieved by any physics accelerator – three times greater than the previous record, which was held by Fermilab.
"LHCb is ready for physics," said the experiment’s spokesman, Andrei Golutvin. "We have a great research programme ahead of us exploring the nature of matter-antimatter asymmetry more profoundly than has ever been done before."
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