Particle physicists seem to have a pretty good handle on the fundamental particles of the universe, but there are some glaring holes in this understanding. Quarks are a good example of this. We know that all nuclear matter is made up of quarks, and we have a pretty good understanding of how two quarks interact at close range. But our quark theory cannot tell us which quark combinations will result in a bound particle or a stable nuclei. All we can go on is experience, and experience has shown that particles with four quarks do not exist. But the situation may have changed with the possible discovery of a new particle containing at least four quarks. Two separate groups, both reporting in Physical Review Letters, have seen evidence for this strange particle, called
Although the data is open to other interpretations, it’s clear that our understanding of quarks has a long way to go.
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