The experiments found hints of the new particle by analysing trillions of proton-proton collisions from the Large Hadron Collider (LHC) in 2011 and 2012. The Standard Model of particle physics predicts that a Higgs boson would decay into different particles - which the LHC experiments then detect.
Both ATLAS and CMS gave the level of significance of the result as 5 sigma on the scale that particle physicists use to describe the certainty of a discovery. One sigma means the results could be random fluctuations in the data, 3 sigma counts as an observation and a 5-sigma result is a discovery. The results presented today are preliminary, as the data from 2012 is still under analysis. The complete analysis is expected to be published around the end of July.
Our Understanding of The Universe is About to Change…
Scientists say their findings are consistent with the theory that attempts to explain how the universe is held together (How Higgs boson lends mass to matter and holds the universe together).
The Higgs boson theory - proposed by British physicist Peter Higgs in the 1960s - suggests the existence of an invisible force field and associated sub-atomic particle that permeates all things, working like glue to give form to stars, planets and even humans.
Without the Higgs particle, the universe would have remained like a soup, the theory says.
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.
Joe Incandela, spokesman for one of the two teams hunting for the Higgs particle told an audience at Cern : "This is a preliminary result, but we think it's very strong and very solid."
Professor Higgs, currently at the University of Edinburgh, welcomed the Cern results, adding: "I never expected this to happen in my lifetime and shall be asking my family to put some champagne in the fridge."
At the LHC, scientists shoot two beams of protons - the "hearts" of atoms - at each other round 27km 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.
What is the Higgs boson?
John Ellis a British theoretical physicist answer the question What is the Higgs boson? in preparation for the press conference following the seminar on LHC 2012 results on the Higgs boson searches, due on July 4 2012 at CERN.
How do Physicists look for it?
What comes next?
Both the ATLAS and CMS experiments have observed a new fundamental particle consistent with the long-sought Higgs boson. Now the exciting work of understanding its significance begins.
The results presented by ATLAS and CMS are labelled "very preliminary", having been prepared for presentation at the major particle physics conference of the year, ICHEP2012, which began in Melbourne on 4 July. The analyses are still being consolidated, and are expected to reach maturity by the end of the month.
Once that has been achieved, work on determining the precise nature of the particle and its significance for our understanding of the universe can begin in earnest. In particle physics parlance, strong evidence means that the probability of an observation being attributable to a statistical fluctuation is less than one per cent. Today, both the ATLAS and CMS experiments are beyond the level of around one per million that's required to claim a discovery, and the experiments should confirm that level of confidence once these analyses are complete.
The hunt for the Higgs particle has long been one of the top priorities for particle physics. The Higgs is associated with a mechanism proposed in the mid-1960s to explain why one of nature's fundamental forces has a very short range while a similar force has infinite range. The forces in question are the electromagnetic force, which brings light to us from the stars, carries electricity around our homes, and gives structure to the atoms and molecules from which we are all made, and the weak force, which drives the energy generating processes of the stars.
The electromagnetic force is carried by particles called photons, which have no mass, whereas the weak force is carried by particles called W and Z that do have mass. Rather like people passing a ball, interacting particles exchange these force carriers. The heavier the ball, the shorter the distance it can be thrown; the heavier the force carrier, the shorter its range. W and Z particles were discovered at CERN in the 1980s, but the mechanism that gives rise to their mass remains to be unlocked, and the Higgs boson is the key.
A simple observation is not enough, however, because the Higgs boson can take many forms. In its basic incarnation, the mechanism is the simplest theoretical model that accounts for the mass difference between photons and W and Z particles, and for the masses of other fundamental particles. But there are other formulations of the mechanism linked to theories such as supersymmetry, which could account for the universe's mysterious dark matter, or to theories predicting extra dimensions of space, which, if verified, would truly revolutionise our understanding of the universe we live in.
So once the discovery is confirmed, the next question is: "What kind of Higgs boson do we have"? Positive identification of the new particle's characteristics will take considerable time and data. It's rather like spotting a familiar face from afar; closer observation might be needed to tell whether it's an old friend who loves coffee, or her identical twin sister who favours tea. But whatever form the Higgs particle takes, our understanding of the universe is about to change.
