The Higgs boson-like particle whose discovery was announced on 4 July looks significantly more certain to exist.

The particle has been the subject of a decades-long hunt as the last missing piece of physics' Standard Model, explaining why matter has mass.

Now one Higgs-hunting team at the Large Hadron Collider report a "5.9 sigma" levels of certainty it exists.

That equates to a one-in-300 million chance that the Higgs does not exist and the results are statistical flukes.

## Statistics of a 'discovery'

- Particle physics has an accepted definition for a "discovery": a five-sigma level of certainty
- The number of standard deviations, or sigmas, is a measure of how unlikely it is that an experimental result is simply down to chance rather than a real effect
- Similarly, tossing a coin and getting a number of heads in a row may just be chance, rather than a sign of a "loaded" coin
- The "three sigma" level represents about the same likelihood of tossing more than eight heads in a row
- Five sigma, on the other hand, would correspond to tossing more than 20 in a row
- Unlikely results can occur if several experiments are being carried out at once - equivalent to several people flipping coins at the same time
- With independent confirmation by other experiments, five-sigma findings become accepted discoveries

The formal threshold for claiming the discovery of a particle is a 5-sigma level - equivalent to a one-in-3.5 million chance.