| I'm not sure about this particular one, but a general idea is that the properties you are measuring in a particle depends on a lot of virtual particles. It's difficult to find an easy example. After some searches in Google I found this unrelated example: http://www.strings.ph.qmul.ac.uk/~bigdraw/feynman/slide3.htm... It has 9 Feynman diagrams. If you look at the top left diagram, there is an electron that enters from the bottom right corner, then it emits a photon that go out thought the top left corner, then the electron goes out through the top left corner. The following two diagrams show the case were the electron emits a second (and third) photon and reabsorbs it, so the second (and third) photons are not visible for the experimenter, they are virtual photons. These additional photons are only important because the change slight the properties of the electron. In the next three diagrams the photon is so strong that it can spontaneously split in another electron and a positron. It looks like a loop/circle, because positrons are like electrons traveling backward in time. They are virtual electrons, and again they are not visible in the lab, they are only important to make a tiny correction to the result of the experiment. The other three diagrams have two virtual electrons, than makes even smaller corrections. And in addition of the virtual electrons, there can be virtual muons and tauons. They are like electrons but with more mass. So the probability of having one of them is smaller, so the correction is smaller. In this case, I think that the correction is so small that it's impossible to measure it. And you can have another virtual particles, like virtual quarks and virtual W, anything that has a charge. Moreover you can have virtual unknown particles (with charge) because nature doesn't care if we know the particle yet or not. But they are heavier, so the correction is negligible. If you change the experiment, and for example make a electron collide with a positron, then the calculations are very similar, but there is more energy laying around, and the corrections from heavy particles are more important, so this variation is more useful to discover new particles. Back to your question ... The new particles are composed by three quarks, but actually they are composed by a lot of gluons and virtual quarks and antiquarks. To do any calculations you have to include a lot of diagrams like in the figure linked above, and a lot more, many many more. IIRC the calculation is so complex that it's not possible to compare the experimental results with theoretical calculations. Perhaps they have some heuristic to compare the results with the results of similar particles. This was probably part of a bigger experiment that produces a lot of particles, and they are trying to classify them in families. And perhaps in the classifications they can spot some strange pattern that may provide a hit that there is a new elementary particle. |