New data narrows down on the Higgs boson 'God particle'
Wednesday 14 Dec 2011 8:15 a.m.
By John Heilprin
Scientists hunting for an elusive subatomic particle say they have found "intriguing hints" - but not definitive proof - that it exists, narrowing down the search for what is believed to be a basic component of the universe. The researchers added that they hope to reach a conclusion on whether the particle exists by next year.
The latest data shows that the mass of the Higgs boson - popularly referred to as the "God particle" - probably falls in the lower end of the spectrum of mass that can be produced by smashing protons together in the huge Large Hadron Collider, researchers from two independent teams said.
The two teams said their data indicates the particle itself may have a mass of between roughly 114 and 130 billion electron volts. One billion electron volts is roughly the mass of a proton. The most likely mass of the Higgs boson is around 124 to 126 billion electron volts, the teams said.
Until Tuesday, the most likely mass was seen as between 114 and 141 billion electron volts. There is still a small possibility that the Higgs could be much more massive and found above 476 billion electron volts, physicists said.
The revelations this week were heavily anticipated by thousands of researchers who hope that the particle, if it exists, can help explain why there is mass in the universe. British physicist Peter Higgs and others theorized the particle's existence more than 40 years ago to explain why fundamental particles - building blocks of the universe - have mass.
Both of the research teams work at CERN, the European Organisation for Nuclear Research near Geneva. CERN runs the $10-billion Large Hadron Collider under the Swiss-French border, a 27km tunnel where high energy beams of protons are sent crashing into each other at incredible speeds.
Collisions between protons smashed in the collider produce energy that in turn creates other particles. On rare occasions, this energy could produce the Higgs particle - if it exists.
Fabiola Gianotti, an Italian physicist who heads the team running the ATLAS experiment, said "the hottest region" is in lower mass ranges of the collider. She said there are indications of the Higgs' existence and that with enough data it could be unambiguously discovered or ruled out next year.
The results rule out several mass or energy ranges for the Higgs with a high degree of confidence, Gianotti said.
"The most important result is that we have been able to restrict the most likely mass region to a very narrow range," she said.
Afterward, Guido Tonelli, lead physicist for the team running the separate CMS experiment, outlined findings similar to those of the ATLAS team, saying the particle is most likely found "in the low mass region" among the spectrum of possible Higgs masses.
CERN's director-general, Rolf Heuer, said "the window for the Higgs mass gets smaller and smaller".
"But be careful - it's intriguing hints," he said. "We have not found it yet, we have not excluded it yet."
Determining what mass the Higgs has helps focus scientists' search for other new physics. For example, a Higgs with a mass around the range of 124 to 126 billion electron volts is "not so bad for supersymmetry," said Heuer, referring to another theory that predicts a partner particle for each one that has already been identified.
The collaborations for the ATLAS and CMS experiments each involve about 3,000 scientists and engineers. They are leading the search for the Higgs, but there are also are several other experiments at CERN looking into other mysteries of the universe.
"We need to get a lot more collisions next year to get a definitive answer to the Shakespearean question, 'To be or not to be,' " Heuer said of the Higgs. "Both experiments have shown that next year very likely we will get an answer that is very solid."
The Higgs boson is hard to find not because it is especially tiny, but rather because it is hard to create, said physicist Howard Gordon of the Brookhaven National Laboratory in Upton, New York, who works with the ATLAS experiment.
Physicists smash protons together at very high energy, and only a minority of collisions will create a Higgs boson. The more energy involved, the higher the fraction of collisions that will make a Higgs.
Frank Wilczek, a Nobel laureate and physics professor at the Massachusetts Institute of Technology, said finding the Higgs boson would tie up a loose end of the so-called standard model of physics, which requires that a Higgs-like particle exists.
Proving the Higgs exists would be "a vindication of the equations we've been using all these years," he said. "Since the equations have worked so brilliantly now for decades, it's really nice to dot the i's and cross the t's," he said.
In addition, if the mass of the Higgs is within a certain range, that would support some other theories that go beyond and improve the standard model, he said. Those theories predict the existence of still other particles to be found. That would mean the Large Hadron Collider "will have another wave of brilliant discoveries in the future," Wilczek said.
The mass range reported Tuesday is "perfect" to meet that requirement, he said.
"Because it fits together so beautifully with everything else we know ... I'm certainly inclined to believe it," he said. He called Tuesday's presentations "awesome ... just beautiful work".