On Tuesday, physicists at the Large Hadron Collider, or LHC, near Geneva, Switzerland, said that data from two independent experiments had narrowed the range of the would-be particle's likely mass.
The Higgs boson is the only particle that the standard model of physics says should be there but hasn't been observed in an experiment. The model describes how matter is built and particles interact.
Proof that the particle exists would help explain a big puzzle: why some objects in the universe—such as the quark, a constituent of protons—have mass, while other objects—such as photons, the constituent of light—possess only energy.
By extension, its discovery would help explain the presence of stars, planets and humans, and thus rank as one of the biggest coups for modern-day physics.
"The Higgs is the missing piece" in the current theory of matter, said Stefan Soldner-Rembold of the University of Manchester, England, who has been on a decade-long quest for the particle, though he wasn't involved in the recent LHC experiments. The latest data may be far from definitive, but "we're going in the direction that it is there," he added.
In 1964, three groups of physicists independently proposed the existence of the Higgs boson. It was named after one of the scientists, Peter Higgs, now an emeritus professor at the University of Edinburgh, Scotland. Thousands of scientists have since tried to chase down the fabled subatomic particle.
Because nobody knows what the mass of a Higgs boson might be, the particle must be hunted indirectly, typically in giant machines that propel particles to near-light speed, then smash them together and generate an array of other subatomic particles.
The hope is that one such particle would be the Higgs itself, though it would almost instantly decay into different combinations of other particles. Finding it would then involve looking for statistically significant "excesses" of those particles.
The latest experiments at LHC, which is overseen by the European particle-physics laboratory CERN, found modest excesses of this sort in the data, a promising sign. One of the experiments, known as Atlas, suggests that Higgs could have a tiny mass, in the range of 116 to 130 gigaelectronvolts, or GeV. The other experiment pegged the particle's mass at 115 to 127 GeV.
On an individual basis, none of these excesses is any more statistically significant than tossing a die and ending up with two sixes in a row. However, physicists are encouraged, because multiple independent measurements indicate that the Higgs may be lurking in the region of 124 to 126 GeV.
"Over the last few weeks, we have started to see an intriguing excess of events around 125 GeV," suggesting a mass about 125 times that of a proton, said CERN researcher Fabiola Gianotti of the Atlas experiment. "This excess may be due to a fluctuation, but it could also be something more interesting. We cannot conclude anything at this stage. We need more study and more data."
How might the Higgs boson confer mass to particles? Physicists have suggested that as the universe cooled after the Big Bang, about 13.7 billion years ago, a force known as the Higgs field formed, along with the particle.
Under this scenario, the Higgs field permeates the universe, and any particles that interact with it are given a mass through the Higgs boson. The more they interact, the heavier they become. Particles that don't interact with the Higgs field are left with no mass at all.
CERN scientists say they plan to refine their analysis and won't be able to offer a definitive conclusion until sometime next year.
It's been an eventful year for the esoteric field of particle physics, especially at CERN. In September, for example, an experiment there reported ghostlike particles known as neutrinos apparently traveling a tiny bit faster than light, an apparent breach of the cosmic speed limit set down by Albert Einstein.
Yet, like many physicists, Dr. Soldner-Rembold of the University of Manchester isn't necessarily eager for the Higgs to be found.
"It would perhaps be even more exciting if it isn't where it's supposed to be," he said. "Then we'd have to come up with something else."
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