Scientists have spent years testing and probing the so-called Standard Model of particle physics, looking for chinks in its armor that may hint at some hitherto undiscovered realm of reality. On Tuesday, two teams of physicists working independently at CERN’s Large Hadron Collider (LHC) reported that they may have just seen traces of a new fundamental particle, which if confirmed, would break the model that has governed our understanding of the cosmos for the past quarter century.
Before delving into the latest findings, described by CERN scientists as “intriguing,” here’s a look at the story so far.
There are four fundamental forces in the universe -- the strong force, the weak force, the electromagnetic force and the gravitational force. Of these, the first three result from the exchange of force-carrier particles, which belong to a broader group called bosons, and whose interactions -- both among themselves and with matter particles such as quarks and leptons -- are explained by the Standard Model.
In 2012, with the discovery of the Higgs boson, which is responsible for imparting mass to all other particles, scientists believed the last missing piece that completed the Standard Model had been found. However, even the completed version of this theory fails to incorporate gravity and explain the origin and preponderance of dark matter and dark energy in the universe.
So, earlier this year, scientists restarted the LHC at an unprecedented energy of 6.5 teraelectronvolts per beam -- compared to 4 TeV per beam in 2012 -- with the aim of either breaking the Standard Model, or bolstering it further. They were also looking for the fabled “graviton” -- a force-carrying particle for gravity -- and evidence of supersymmetry -- an extension of the Standard Model that predicts the existence of more massive “super partners” for every known particle.
On Tuesday, CERN researchers announced that both the CMS and ATLAS detectors had found, while sifting through the debris of proton-proton collisions, an unexpected excess of pairs of photons carrying around 750 gigaelectronvolts (GeV) of combined energy. The physicists said that this might be a telltale sign of a particle, about six times more massive than the Higgs boson, decaying into two photons of equal mass.
However, their statements were accompanied by a bunch of caveats, warning that the findings were far from conclusive and may very well turn out to be a statistical fluke or anomaly. The statistical significance of the discovery is still very low, falling way below the gold standard of five-sigma.
“What is nice is that it is not a particularly crazy signal, in a quite clean channel,” Nima Arkani-Hamed, a particle theorist at the Institute for Advanced Study in Princeton, New Jersey, reportedly said. “So, while we are nowhere near moving champagne even vaguely close to the fridge, it is intriguing.”
Here’s the kicker: Since the Higgs boson was the last missing piece from the Standard Model, the only way another, more massive particle can be incorporated is by discarding the Standard Model and opening an entirely new chapter in the field of particle physics.
“The more nonstandard the better,” Joe Lykken, the director of research at the Fermi National Accelerator Laboratory and a member of one of the CERN teams, reportedly said. “It will give people a lot to think about.”