CERN achieves 7 TeV collisions at Large Hadron Collider
Mar 30, 2010 29 comments
Physicists at CERN in Geneva have achieved the first 7 TeV proton–proton collisions at the Large Hadron Collider (LHC).
The first collisions took place at 1 p.m. local time and are the most energetic ever achieved in a particle accelerator.
More significantly, today marks the beginning of the LHC physics programme, which will test and scrutinize the Standard Model of particle physics.
"It's a great day to be a particle physicist," said CERN director-general Rolf-Dieter Heuer. "A lot of people have waited a long time for this moment, but their patience and dedication is starting to pay dividends," he added.
Heuer's delight at the LHC finally colliding protons 18 months after the September 2008 accident is shared by Fabiola Gianotti, spokesperson for the ATLAS experiment. "The prevailing sentiment is emotion," said Gianotti, speaking shortly after the first collisions were announced. "Behind these instruments are people with their feelings, with their frustrations, with their ambitions – it is the end of 20 years' hard work within the scientific community."
All detectors working
The first collisions took place at lunchtime following two earlier attempts that had to be abandoned due to faults in the beamline power supply. The first pair of beams were "dumped" by accelerator scientists after detecting a minor problem with a power supply. The second attempt was aborted by the LHC's early-warning system, which was installed after the accident in 2008 that punctured the machine's liquid-helium cooling system
All of CERN's detectors are now recording collisions and early reactions at CERN suggest that scientists are impressed with what they are seeing. "We are completely ready to start analysing data today because our detector is perfectly aligned and calibrated, and we have already produced meaningful results published in a paper last week," said Pauline Gagnon of the ATLAS collaboration.
The ATLAS experiment will search for, among other things, the Higgs boson – the missing piece in the Standard Model of particle physics that could explain how particles acquire their mass. Precision measurements of known Standard Model particles mean that its mass is unlikely to be more than 186 GeV. Direct searches made at CERN's Large Electron–Positron collider (LEP) – the forerunner to the LHC – have ruled out a Higgs that is lighter than 114 GeV.
Another experiment at CERN is the LHCb, which will allow researchers to study the difference between matter and antimatter with unprecedented accuracy. Its spokesperson Andrei Golutvin said that he was already intrigued by the detections he is seeing. "Today, we celebrate the start of new life where Monte Carlo simulations are replaced with real data," he said. "Let us hope that nature is kind to us."
CERN's plan is to run continuously for a period of 18–24 months, with a short technical stop at the end of 2010. Experiments will run throughout this time, with researchers expecting to accumulate one "inverse femtobarn" of data – roughly 10 trillion proton–proton collisions. The LHC will shut down in 2012 to prepare it to go straight to maximum-energy 14 TeV collisions.
Steve Myers, CERN's director for accelerators and technology, is confident about reaching higher-energy collisions. "We are convinced that, without too much trouble, we can go to 13 TeV, and I am very confident we can go beyond that to 14, some time in 2013," he said.
Looking to the longer term, Heuer today reiterated his desire for the Geneva laboratory to host the next big experiment in particle physics after the LHC. "The energy of this collider will be determined by the results of the LHC," said the CERN boss. "It would be bad management if we would not put the hat in the ring."
About the author
James Dacey is a reporter for physicsworld.com and is reporting from CERN