Just days after U.S. particle physicists were told they would have to shutter their accelerator later this year—so ending their hopes of finding the elusive Higgs boson—their European competitors at CERN near Geneva, Switzerland, look set to continue the chase for an extra year before a scheduled shutdown of their machine, the Large Hadron Collider (LHC).
The Higgs is the most eagerly sought goal for physicists seeking to understand nature's fundamental particles and forces because it is the key part of the mechanism that explains why particles have mass. Researchers running the 25-year-old Tevatron accelerator at Fermi National Accelerator Laboratory near Chicago, Illinois, wanted to keep it on line until 2014 in the hope of gathering enough data to prove the Higgs' existence. But financial constraints mean the Tevatron will have to shut in September.
The newer and more powerful LHC has a much greater chance of finding the particle, but teething troubles with the superconducting magnets that bend speeding protons around the ring mean that some modifications need to be made before the collider can reach its full design energy—colliding particles with a combined energy of 14 teraelectron volts (TeV). The lab had planned to shut the LHC down at the end of this year and make the modifications during 2012, but as LHC operators reported during a meeting of staff members in the French alpine town of Chamonix this week, the accelerator has been running so well over the past year that they feel confident enough to put off the modifications.
It's not a done deal yet, says CERN spokesperson James Gillies: The LHC's machine advisory committee will meet on Sunday and will report to CERN management on Monday before an official decision is made. "It was thoroughly discussed" at Chamonix, says Guido Tonelli, spokesperson for CMS, one of the four huge detectors that operate around the LHC, "and there was a unanimous consensus to move this way." If the LHC is run until the end of 2012, "we will have enough data that we might be able to ... exclude [the existence of] the Higgs from large mass regions and possibly even discover it, if nature is kind to us," Tonelli says.
Because of concerns about the magnets, the LHC operated only up to a maximum energy of 7 TeV during 2010, but there was also discussion at Chamonix about easing that up to 8 TeV. The collider "has been running very sweetly through 2010, so some are reluctant to change anything," Tonelli says. "It's not a very large increase, but there are still risks." He thinks CERN management will opt for prudence during 2011 and stick to 7 TeV, but with another year's data on the collider's performance, next year's meeting at Chamonix may revisit the issue. There are already plans to increase the luminosity—the number of particles—of the LHC's beam this year, and that will provide researchers with more collisions.
Speaking from the train on his way back from Chamonix, Tonelli says there is quite some optimism that the LHC will "give major answers" this year, possibly including evidence of supersymmetry and extra dimensions. Any suggestions of the Higgs would likely not appear until 2012.