GENEVA — Scientists believe the ‘‘God particle’’ that might explain the underpinnings of the universe is real, and they are about to present their evidence to the world.
Physicists at the world’s biggest atom smasher plan to announce Wednesday that they have nearly confirmed the primary plank of a theory that could shape the scientific understanding of all matter.
The focus of the excitement is the Higgs boson, a subatomic particle that could help explain why matter has mass, which combines with gravity to give an object weight.
Researchers at the European Organization for Nuclear Research say that they have compiled vast amounts of data that measure and reveal the shadow of the particle — all but proving it exists, even though it has never actually been glimpsed.
Two independent teams of physicists are cautious after decades of work and billions of dollars spent. They do not plan to use the word ‘‘discovery,’’ but they say they will come as close as possible to asserting that the particle exists.
Meenakshi Narain, a physics professor at Brown University who works on one of the teams, said that although she could not disclose what will be announced on Wednesday, this was a “once in a lifetime event,” because the experiments have provided enough data to give “at least the first hints of it in a significant way,” or to rule out the existence of Higgs.
She and her students and her children will be in the laboratory 3 a.m. Wednesday, watching the announcement streaming on the Web.
If the Higgs is discovered, “this would be really something very, very, very exciting,” Narain said. “And if we were to not find it . . . it would be even more exciting because we’d have to go back to the chalkboard and figure out what was going on.”
Markus Klute, an MIT physicist also involved in the Higgs hunt, said anticipation is high. Klute said in a phone interview from Geneva that he will depart Tuesday for Melbourne, where he will present the results from one of the analyses that underlies the new finding to an international particle physics conference.
“There’s nothing routine in this,” Klute said. “It’s incredibly exciting to look at this data. You have to understand, the community is looking for evidence for this new particle for the last 40 years. This will tell us about the presence or not of this particle.”
Frank Wilczek, a Nobel laureate and physics professor at MIT, said he plans to either stay up late or get up early to watch the scientific presentation. He said that while he had no inside information, it seemed likely that even if the teams did not announce the actual discovery of the particle, they had come very close to it.
“It’s a very sort of historic moment for physics, because we had this standard model working extremely well and going from triumph to triumph, and this is kind of the last important piece,” Wilczek said. He also said he hoped that the discovery would finally persuade his colleague at MIT, Janet Conrad, to concede that he had won a bet they made in 2005.
Wilczek had predicted the European Organization for Nuclear Research’s atom smasher, the Large Hadron Collider, would measure the Higgs, and that the particle would be below a certain mass. He said he hoped that after this press conference, Conrad would give him his prize – 10 chocolate wafers the same size as the Nobel Prize, wrapped in gold foil.
The $10 billion collider on the Swiss-French border has been creating high-energy collisions of protons to investigate dark matter, antimatter, and the creation of the universe, which many theorize occurred in a massive explosion known as the Big Bang.
The phrase ‘‘God particle,’’ coined by Nobel Prize-winning physicist Leon Lederman, is used by laymen, not physicists, more as an explanation for how the subatomic universe works than how it all started.
Though an impenetrable concept to many, the Higgs boson explains how subatomic particles, such as electrons, protons, and neutrons, were formed and what gives them their mass.
The answer came in a theory first proposed by Scottish physicist Peter Higgs and others in the 1960s. It envisioned an energy field in which particles interact with a key particle, the Higgs boson. The idea is that other particles attract Higgs bosons and the more they attract, the bigger their mass will be.
Rob Roser, who leads the search for the Higgs boson at the Fermilab in Chicago, said: ‘‘Particle physicists have a very high standard for what it takes to be a discovery,’’ and he thinks it is a hair’s breadth away.
The Fermilab, which has a competing atom smasher, reported its final results Monday after shutting down last year.
It said its data did not settle the question of the Higgs boson, but it came tantalizingly close.
Officially, the European Organization for Nuclear Research will present its evidence this week at a physics conference in Australia but plans to accompany the announcement with meetings in Geneva.
The two teams, ATLAS and CMS, then plan to publicly unveil more data on the Higgs boson at physics meetings in October and December.
Sean M. Carroll, a California Institute of Technology physicist, said if both ATLAS and CMS have independently reached these high thresholds on the Higgs boson, then ‘‘only the most curmudgeonly will not believe that they have found it.’’Carolyn Y. Johnson of the Globe staff contributed to this report.