avouleance2nd said:
hiei82 said:
That was mentioned a fair bit, so what exactly does the sigma mean in that context?
"sigma" is the greek symbol that is used to denote "standard deviation" in science and mathematics.
The problem with subatomic particles is that they cannot observe them directly in most cases. instead, they need to observe the effect the particle would have to predict the existence of particle itself. A good example of this is the neutrino, which cannot be detected directly because of it's speed and ability to pass through most forms of matter with ease (it would take 2 years of a neutrino passing through lead before it would be stopped) Instead, they send it through water and watch for the effect it causes (Cherenkov radiation) to "see" it.
The Higgs is even harder to detect, because it has no active effect (it "gives" mass to matter). So, what CERN did, is that collided millions of particles millions of times, which split the particles they shot and recombined them into other, different, particles - the Higgs included. They couldn't control what they made, so they just let probability do what it does best. They shot tons of particles and measured the results so that they could look for the distribution of high energy particles. Because of the theory of the standard model (an equation that predicts what particles exist), they knew what the distribution should look like if the Higgs existed and what it should look like if it didn't. Then, they mapped the data they got from the LHC and tried to match it up to what they predicted.
When they say they "predict the Higgs-Boson's existence within 5 sigma" that means that the variation of their results is so close, they have 5 sigma's (standard deviations) of "buffer." That means that, statistically, there is only about a 1 in 2 million chance they are wrong. The reason that 5 sigma is so significant is that 5 sigma is the accepted mathematical-variation-standard for particle physics (i.e. they can say they found the Higgs-Boson with such a degree of certainty that they can use the data as scientific proof)