Hints of the last undiscovered particle in the Standard Model of Physics may have been detected by two separate experiments at the world's biggest particle accelerator.
Researchers at the Large Hadron Collider have glimpsed signals that could point to the existence of the Higgs boson — nicknamed the "god particle" by 1988 Nobel Prize winner Leon Lederman — an elusive subatomic particle theorized to impart mass to other particles.
"We saw some tantalizing hints today," said Rolf-Dieter Heuer, director-general of CERN, the European Organization for Nuclear Research, Tuesday, after the results of experiments known as ATLAS and CMS were presented at a public lecture. The ATLAS collaboration includes a number of Canadian scientists.
Hints of the last undiscovered particle in the Standard Model of Physics may have been detected by two separate experiments at the world's biggest particle accelerator.
Researchers at the Large Hadron Collider have glimpsed signals that could point to the existence of the Higgs boson — nicknamed the "god particle" by 1988 Nobel Prize winner Leon Lederman — an elusive subatomic particle theorized to impart mass to other particles.
"We saw some tantalizing hints today," said Rolf-Dieter Heuer, director-general of CERN, the European Organization for Nuclear Research, Tuesday, after the results of experiments known as ATLAS and CMS were presented at a public lecture. The ATLAS collaboration includes a number of Canadian scientists.
Both experiments, which involve about 5000 scientists altogether, showed signals for a mass between 115 and 130 GeV — the lower end of the range scanned by the scientists — that could indicate the presence of a new particle.
The researchers have now all but ruled out the possibility (with 99 per cent confidence) that the Higgs boson has a mass between 128 and 525 GeV.
However, the researchers warned that not enough data has been collected to make statistically sure that the apparent "Higgs boson" signals they saw are not due to fluctuations in background signals caused by other particles and processes. Heuer warned that the results are preliminary, as they involve very small numbers of signals.
"Please be prudent," he said. "We have not found it yet. We have not excluded it. Stay tuned for next year."
In 2012, scientists at the two experiments expect to collect four times the amount of data they collected in 2011, increasing the number of signals they see and reducing the statistical error significantly.
Fabiola Gianotti, spokeswoman for the ATLAS experiment, said that means the Higgs boson could be unambiguously discovered or ruled out by ATLAS in 2012.
How to hunt for Higgs
Inside the Large Hadron Collider, the ATLAS experiment collides protons, some of the building blocks of atoms, at an energy of 3500 GeV. The collisions are expected to produce Higgs bosons, which have an unknown mass.
Each proton is made up of smaller particles called quarks and gluons that can have a wide range of energies following the collisions. At that point, the particles coming out of the collision hit a detector, which measures their energies. Since they are travelling close to the speed of light, their energies and their masses are roughly equivalent.
Theory predicts how many Higgs bosons should be produced by a collision of a certain energy if it has a certain mass.
"Within 10 per cent, we know how many of them should be and how many our detector should have seen," said William Trischuk, a University of Toronto physicist involved in the ATLAS experiment.
Higgs bosons are extremely short-lived and decay before they can ever be detected. However, when they decay, a number of slightly longer-lived particles are expected to be produced. Those in turn decay into particles that can be detected.
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