Advancing science, pushing technology, and bringing together scientists from countries around the globe are among the benefits of the Large Hadron Collider, according to Lyn Evans, project leader for the LHC. He outlined the status of the LHC and the importance of large international collaborations at an event on Capitol Hill in November sponsored by APS, the American Association for the Advancement of Science, and the British Embassy.
CERN, the European Center for Nuclear Research, was established in 1954, nine years after the end of World War II. Geneva was selected as the site for the laboratory, said Evans, because “Geneva was neutral, and it was cheap. It is still neutral.”
As an international laboratory, one of CERN’s goals has been to bring scientists together across national boundaries and train students in an international environment. “An essential feature of CERN is collaboration,” said Evans. CERN has 2415 staff, 730 Fellows and Associates, and 9133 users from all over the world. The United States is an observer state; 1278 of CERN’s users come from the US.
In his talk, Evans described the areas where the LHC could make important discoveries. “The first real mystery is what is the origin of mass,” Evans said. “It may seem a strange question to ask,” he said, since mass seems intuitive to most people. Theory predicts the existence of a Higgs boson, which gives mass to other particles. The LHC has been designed to cover the mass range where the Higgs is predicted to be. “If the Higgs exists, the LHC will find it,” Evans said.
Other questions the LHC could potentially answer include the origin of the matter/antimatter asymmetry and the nature of dark matter and dark energy. It may also pick up evidence of supersymmetry or extra dimensions, Evans said. While the Higgs has been promoted as the main discovery the LHC is expected to make, Evans emphasized that the LHC could find many things we haven’t even considered yet. “I think the Higgs is oversold,” he told APS News. “The LHC is a discovery machine.”
In response to a question about the timescale for discoveries, Evans pointed out that experimental results will not come out immediately once the machine turns on again. The LHC will be running for many years, and it might take several years before significant results come in. The next steps for the field of particle physics will depend on what the LHC finds, Evans said.
The LHC is 17 miles in circumference, and will accelerate protons to 7 trillion electron volts. Accelerators have grown exponentially in size and energy over the years, Evans pointed out. The first circular accelerator, built at Berkeley in 1930, was only five inches in diameter and accelerated ions to 80,000 electron volts.
The improvements over the years have been achieved not by bigger and bigger budgets, but by pushing technology, Evans said. Since the 1980s, superconductivity has been the key to increasing the energy accelerators can reach. The LHC uses 7000 km of superconducting Nb-Ti cable and 23 km of superconducting magnets. An equivalent accelerator without superconducting technology would have to be much larger and consume much more power, Evans said.
With the uncertainty in the US budget cycle, one never knows from year to year what will happen, but the LHC has been lucky so far (unlike, for instance, ITER), Evans said. “The best we can hope for is stability in budget.”
The LHC was shut down shortly after its initial opening in September 2008 due to an electrical failure that caused a helium leak, which damaged some of the magnets. The failure was caused by one bad connection among 10,000 electrical connections. “We did the best we could with quality control,” Evans told APS News. “It’s a good thing that it happened now,” rather than later, he said. Evans added that work had been done on figuring out how to spot such defects in the future to prevent further problems.
It has been estimated that it will cost $21 million to repair the problem. The LHC is not expected to restart until summer 2009. “When you get a problem, it’s a long time to make a repair,” said Evans.
Once the LHC does restart, there will soon be a massive amount of data to be processed after the LHC gets running again. The Grid computing network will make traveling to CERN unnecessary for many of the scientists who will analyze LHC data. “People do not need to come to CERN. They can be analyzing data in their home institutes,” Evans said.
While organizing the huge international collaborations working on the LHC could potentially be “a big sociological problem,” these groups have been well organized, have operated with mutual respect, and have had no major problems, Evans said. “CERN’s mission in 1954 was to bring nations together, and it is still doing it.”