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Answers ahead for physics' puzzles

The CERN Neutrinos to Gran Sasso experiment sends muon neutrinos through a tunnel at the French-Swiss border in the direction of a detector in Italy, more than 450 miles away. One of the group's experiments, known as OPERA, turned up evidence that neutrinos may travel faster than light.



This year, particle physicists are aiming to get definitive answers to the questions that consumed them last year: Does the Higgs boson, potentially the final fundamental piece of the Standard Model puzzle, actually exist? Could there be new physics beyond the Standard Model, which is arguably the most successful scientific theory of the 20th century?

And just as importantly, can neutrinos really fly faster than light, as findings from Italian lab suggested last year?

"I have difficulty to believe it, because nothing in Italy arrives ahead of time." Sergio Bertolucci, research director at Europe's CERN particle physics center, joked today during a scientific meeting in Vancouver, Canada.

Physicists recapped the past year's results and looked ahead to the next year during sessions at the annual meeting of the American Association for the Advancement of Science — and if their expectations come to pass, 2012 could be a big year for textbook editors.


First, about those neutrinos: Experiments conducted by the OPERA collaboration at CERN on the French-Swiss border and at Italy's Gran Sasso National Laboratory clocked particles traveling the 450 miles (732 kilometers) between the labs at speeds slightly higher than the speed of light. That would run counter to a century's worth of special-relativity experiments, which has led most scientists to suspect some subtle factor went unaccounted for in the experiment. However, the skeptics haven't yet shown definitively where where the OPERA scientists went wrong, which "means that essentially they've done their job," Bertolucci said.

He said there were five efforts under way to re-examine or replicate the OPERA team's experimental results. One such effort would involve the MINOS neutrino experiment headquartered at Fermilab in Illinois. Rob Roser, a staff scientist at Fermilab, said the neutrino test required the installation of more sensitive detection equipment, and now that the equipment is ready, data would be collected in April. The results of the replication efforts should be in hand by the end of the year. 

The faster-than-light effect is so subtle that physicists would find it hard to accept even if a similar effect is detected by other experiments. But Bertolucci recalled that similarly unexpected results from the Michelson-Morley experiment, more than a century ago, eventually led to Albert Einstein's revolutionary work on relativity.

"We have to just keep an open mind," Bertolucci said.

Quest for the Higgs
The discovery of the Higgs boson, the particle that could explain the phenomenon of mass and masslessness, is the year's other coming attraction in particle physics. For the past few years, Fermilab's Tevatron and CERN's Large Hadron Collider have been in friendly competition to pick up the first hints of the particle's existence. And even though the Tevatron was shut down last September, the teams analyzing the last of their results could still "steal Sergio's thunder," Roser said.

Roser, who is the leader of the Tevatron's CDF collaboration, said scientists were in the "final throes" of data analysis and would announce their results relating to the Higgs boson at a March conference in Italy.

"We will be able to say something interesting, though whether it's that we don’t see it or we do see it remains to be seen," he said.

Late last year, the LHC teams said they saw hints that the Higgs boson might exist at a mass-energy level of 125 billion electron volts, or 125 GeV. Those hints were too tentative to count as a discovery, however, and it sounds as if the same might hold true for the Tevatron results. Roser said he and his colleagues think the Tevatron's detectors could spot a 125 GeV Higgs boson at a 3-sigma confidence level — which is short of the standard for a discovery.

Bertolucci repeated his view that the LHC will determine "by the end of 2012" whether or not the type of Higgs boson predicted by the Standard Model exists. Workers are due to clear out of the LHC's underground tunnels next week, and after a cooldown period, the collider will once again start shooting proton beams into detectors at 99.999999 percent of the speed of light.

Bertolucci said the LHC has grown "from an infant to a very, very healthy teenager" over the past year, and CERN's plans call for the beam energies to be ramped up from 3.5 trillion to 4 trillion electron volts this year.

The Higgs boson ranks as one of physics' most famous "known unknowns," Bertolucci said. "But we hope for unknown unknowns," he added. 2012 could be the year that the LHC points to new physics beyond the Standard Model, perhaps having to do with supersymmetry, mini-black holes or extra dimensions.

If the Higgs is found, that would confirm once again that the Standard Model provides the correct description of the subatomic world, and physicists would rejoice. But Bertolucci said "I would be more excited if we don't find it."

"If the Higgs mechanism is not there, another mechanism must be there," he explained. It turns out that particle physicists, like fans of detective novels, love a mystery.

Closing in on the W boson
While we're waiting for the next chapter in the Higgs quest, Fermilab's scientists are getting ready to unveil yet another piece of the subatomic particle puzzle. They'll announce the latest estimate of the mass of the W boson on Feb. 23, Roser said. That's significant, not only because it helps nail down another key value in the Standard Model, but also because an accurate measurement of the W boson can tell physicists more precisely where to look for evidence of the Higgs boson. Symmetry magazine illustrates the point with plush toys in a vise.

More on the frontiers of physics:

More from the AAAS meeting in Vancouver:


Alan Boyle is science editor at msnbc.com. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding the Cosmic Log Google+ page to your circles. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.