The hunt for the fabled “God particle” that lends mass to matter and holds the universe together could soon be over.
Scientists giving a progress report on the search today are expected to say they are almost at the point of confirming the existence of the Higgs boson.
Almost, but not quite. The process of proving the Higgs is real is a gradual one, similar to getting closer to a familiar face seen from afar.
In December last year scientists at the Large Hadron Collider (LHC) – the “Big Bang” particle accelerator which recreates conditions a billionth of a second after the birth of the universe – revealed they had caught a first tantalising glimpse of the Higgs.
Since then they have sifted through vast quantities of data from innumerable high energy collisions in an effort to reduce the odds of being wrong.
A statistical standard of proof known as “five sigma” would be the ultimate confirmation of a discovery. In this case, the chances of a mistake are one in a million.
Today the scientists at Cern, the European Organisation for Nuclear Research in Geneva, are likely to announce a significant step further towards the five sigma goal. Possibly, they might even be at “four sigma”, a hair’s-breadth away from having the Higgs in their grasp. In that case the final “discovery” of the Higgs particle will be virtually a foregone conclusion.
Cern’s director for research and computing, Sergio Bertolucci, said: “We now have more than double the data we had last year. That should be enough to see whether the trends we were seeing in the 2011 data are still there, or whether they have gone away. It’s a very exciting time.”
At the LHC, scientists shoot two beams of protons – the “hearts” of atoms - at each other round 27 kilometres of circular tunnels at almost the speed of light.
When the protons smash together the enormous energies involved cause them to decay into an array of more fundamental particles. These may then decay further into yet more particles.
By following the decay patterns, scientists hope to see the “fingerprint” of the Higgs boson.
Physicists need the Higgs to plug a gaping hole in the “Standard Model”, the theory that explains all the particles, forces and interactions making up the universe.
So far nothing has been observed to account for mass, and the fact that some particles weigh more than others.
According to the theory, the Higgs boson is the emissary of an all-pervading “Higgs field” that gives matter mass. The more particles interact with the field, the more massive they become and the heavier they are.
A Standard Model universe without the Higgs boson could not exist. Everything would behave as light does, floating freely and not combining with anything else. There would be no atoms, made from conglomerations of protons, neutrons and electrons, no ordinary matter, and no us.
Finding no evidence of the Higgs would mean tearing up the Standard Model and going back to the drawing board with a completely new set of theories.