Recently,the higgs bosons are discovered in LHC. My question is
How did they come to know that the particle that are created are actually Higgs boson?
On the basis of which properties,they confirmed them as Higgs boson?
Answer
The experiments have measured the number of events in which the Higgs boson was produced and decayed into various final particles such as a pair of photons; pair of Z bosons; pair of tau leptons; bottom quark-antiquark pair, and a few others. All these numbers are compatible, within the current error margin, with the prediction of the Standard Model Higgs boson (the diphoton decay rate may be currently higher by 70% or so and it hasn't been fully updated, but all the others are currently "totally well-behaved").
There are specific polarization-based experiments that show that the particle is almost certainly a scalar, not a pseudoscalar, and it must have spin $j=0$.
If the particle were a "completely, qualitatively different" particle than the Higgs boson, the numbers of events mentioned above would differ from the Standard Model Higgs values (theoretically calculable and experimentally measured) by a lot, typically by many orders of magnitude. So it's clearly "something like the Higgs boson". Moreover, a Higgs boson is needed for the Standard Model to be consistent.
At this moment, it remarkably barks like the SM Higgs boson and does everything else like one, too. At the current accuracy, we may see it is the Standard Model Higgs boson. In fact, our accuracy and certainty that it is so is no longer too different from the certainty with which we may say that what we call the W-bosons are W-bosons and what we call the Z-bosons are Z-bosons. If you were impartial, you should have asked the same doubtful questions about the W-bosons or Z-bosons or other particles, too. The Higgs boson is a newer particle but it's already a part of the standard collection that agrees with the Standard Model so well that it can't be quite a coincidence.
The fact that the discovered July 4th Higgs boson behaves just like the Standard Model Higgs boson is increasingly clear and increasingly frustrating because it gives us no hints how to go beyond the Standard Model so far. See stories such as
Sometime in the future, perhaps distant future, new physics will be discovered, e.g. new particles, and they will modify the whole theory including the identity of the Higgs sector. But they will slightly modify the Z-bosons, W-bosons, and all other particles as well. In some sense, it will be proved that they're not the Standard Model Z-bosons or W-bosons, either. It makes no sense to single out the Higgs boson (although when it comes to the Higgs, there are best reasons to think it has "siblings"). The whole theory will ultimately be shown to differ from the Standard Model.
At this moment, however, once again, all the observations at the LHC agree with the Standard Model which is why it is legitimate to use the Standard Model terminology for all the particles and interactions we're observing.
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