||This DZero event is not thought to have come from a Higgs boson, but an event in which a Higgs boson decayed into a pair of Z bosons would look very similar.|
If we find the Higgs boson, we won't see the particle itself. Instead, we will see its decay products interacting with the detector. To find out if the original particle is the Higgs, we do particle physics forensics.
If Higgs theory is correct and it exists in the suspected mass range, the Higgs boson has a lifetime of about 10-22 seconds. Even if it is moving at nearly the speed of light, the Higgs boson will travel a distance only a few times the size of a proton before it decays. That's too quick for us to observe, so we have to look at the end result. For simplicity, let's say the Higgs boson decays into two Z bosons, even though that's rare in that mass range.
If one Z boson decays into an electron-positron pair, while the other Z boson decays into a matter-antimatter pair of muons, we can see the relatively stable electrons and muons in the detector.
If we only see the electrons and muons, how do we know what started the decay chain? Referred to as the parent, the original particle decays into daughter particles, their decay products are granddaughter particles and so on. To determine the original ancestor, we exploit basic energy and momentum conservation laws. The generations have exactly the same energy and momentum, since energy and momentum are conserved. For instance, if we take the two muon granddaughter particles and precisely measure their energy and momentum, we can combine them and determine the energy and momentum of their parent, one of the Z particles. Do the same for the other Z particle, and we can combine the energy and momentum of the two daughter Z bosons to determine the energy and momentum of the parent particle that might be a Higgs boson.
Click here to read the expanded column on how decay products lead to the original product.
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