New Delhi, July 4: Scientists today announced the discovery of a new subatomic particle that seems to behave like the Higgs boson, the last piece of an elegant theory of the building blocks of the universe predicted 48 years ago but never seen.
The particle detected in a laboratory in Geneva has signatures remarkably similar to those expected from the Higgs boson, sometimes dubbed the God particle. But the scientists have not yet named it as they want to be sure that it isn’t an imposter.
Two experimental teams at the European Organisation for Nuclear Research, or CERN, today reported that they have independently observed a particle that has a mass about 126 times that of a proton.
Both research teams detected its signatures in the tumultuous debris of subatomic particles created during proton-proton collisions in CERN’s giant particle accelerator called the Large Hadron Collider.
“We have a discovery,” Rolf Heuer, the CERN director-general said, moments after a researcher from each team presented the findings at a seminar this morning. “We have observation of a new particle consistent with the Higgs boson,” Heuer said.
Scientists have been looking for the Higgs boson for more than two decades, using particle accelerators and high energy subatomic particle collisions to experimentally confirm the particle British physicist Peter Higgs had proposed in 1964.
The Higgs boson is the last missing piece of the Standard Model theory of physics that explains almost all the properties of fundamental particles and forces of nature, except gravity.
But the Standard Model doesn’t explain how particles have mass. “This is why the Higgs hypothesis is so important to us,” said Ashutosh Kotwal, an India-born physicist at Duke University in the US, who leads a Higgs search team at ATLAS, one of the two experiments at LHC.
“It solves one of the biggest mysteries in physics — how the fundamental particles acquire mass. Without mass, we can’t imagine the universe as we know it. Our very existence thus depends on the Higgs,” Kotwal said tonight.
In December 2011, CERN teams had said that they had found tantalising hints of the Higgs boson but declared that their results were inconclusive.
Physicists involved in the Higgs search said the results presented today suggest that the chance that the signals of the new particle observed is due to an error or statistical fluctuations is less than 3 in 10 million.
“We’ve found evidence for a unique particle that roughly fits the description of the Higgs boson,” said Vivek Sharma, an India-educated physicist at the University of California, San Diego, who has been involved in the search for the Higgs at the LHC through the second experiment called CMS.
“In US hunting circles, there’s a saying that if something walks like a duck and quacks like a duck, it must be a duck. But that’s not the way science advances. We need more evidence to say for certain that this is indeed the Higgs boson of the Standard Model. It’s like using genetic fingerprints to show it’s a duck,” Sharma said.
The search for the Higgs boson is among the longest-running and most expensive of scientific endeavours, an international effort with researchers from over 40 countries, including India, helping design, build, and conduct experiments at the LHC.
“It’s an emotional moment. Today’s results are the culmination of 20 years of efforts,” said Fabiola Gianotti, an Italian physicist who presented the results from ATLAS today. “But it’s also a starting point for more research,” Gianotti told The Telegraph.
In the coming months, researchers hope to continue using collision data from the LHC to determine the precise nature of the new particle, specifically investigate whether its behaviour perfectly matches what the Standard Model theory has predicted.
The Higgs boson which belongs to a class of particles named after the 20th century Indian physicist Satyendra Nath Bose, has only a fleeting existence and decays through multiple routes, or channels — disintegrating into energy or other subatomic particles.
The Standard Model theory predicts the ratios of these multiple decay channels and scientists plan to spend the next several months trying to determine whether the new particle satisfies these rules.
Physicists believe that other particles — imposters — may also mimic the Higgs boson.
“We’re now asking: is this the Higgs boson predicted by the Standard Model, or could this be the lightest of five Higgs bosons predicted by the theory called super-symmetry, an extension of the Standard Model?” said Sudeshna Banerjee, a physicist at the Tata Institute of Fundamental Research, Mumbai, who’s looking for evidence for physics beyond the Standard Model at the LHC.
Whatever the answer that emerges in the future, scientists were celebrating today. “It’s a fantastic day for science,” said Sharma.
“This is potentially a historic and profound step forward in our understanding of the underlying structure of our universe,” said Joe Incandela, a senior physicist from the University of California, Santa Barbara, and spokesperson for the CMS experiment.
The possibility that the new particle might not turn out to be the Higgs boson predicted by the Standard Model doesn’t seem to be worrying physicists. “We are happiest when Nature throws surprises at us,” said Kotwal.
“A variant of the Higgs boson would mean new physics and new particles,” said Andy Lankford, a physicist from the University of California, Irvine, and deputy spokesperson for the ATLAS experiment.