The standard model of particle physics is often illustrated as a simple grid showing the 17 basic particles (shown above). But an alternative way of visualising it reveals the complex rules that govern how the particles and forces interact.
This article is part of a special series on the standard model, in which we explore:
The conventional grid shows three generations of quarks (which feel the strong force) and leptons (which don’t). Then there are the bosons that mediate three of the fundamental forces of nature – the strong and weak nuclear forces and electromagnetism. But it doesn’t give us the full picture.
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For one, there are parts missing, like the fact that most particles can occur in two forms of a property called handedness: right-handed and left-handed. It also tells us nothing about which particles feel which forces. There are mysteries it glosses over, too, like the fact there are no right-handed neutrinos, at least that we know of. “The standard grid, as lovely as it is, looks finished,” says , a theoretical physicist at the Fermi National Accelerator Laboratory in Illinois. “But the standard model is not finished.”
Quigg thought we needed a new way to visualise the theory that reflected its messiness. In 2005, he came up with his answer: the double simplex (shown above). Made of two pyramids, linked by the Higgs boson, one half represents left-handed particles and the other right-handed ones. Each pyramid vertex groups generations of related particles together.
By using lines of different colours, the double simplex shows how particles interact through different forces. The lack of right-handed neutrinos is shown by the smaller number of particles in the right-handed pyramid. Here, too, you can see there are no weak interactions inside each shell, meaning that right-handed quarks and leptons can’t switch between different flavours or generations. “The difference between left-handed and right-handed particles is one of the big mysteries of the standard model,” says Quigg. In the usual grid, these complexities are hidden, but the double simplex celebrates them.
