From supernovas to rain, humans to amoebas, all matter can be broken down into three key particles: electrons, protons, and neutrons. But over the years, scientists discovered even more particles, and that neutrons and protons could be broken down into even smaller parts, called elementary particles. Physicists created a theory called the Standard Model to interpret how elementary particles comprise the universe. The model is often depicted as a gigantic equation or as a periodic table of particles as a way to describe complex particle interactions. Strangely enough, some of these interactions are reminiscent of a time in our lives that we’re all too familiar with – high school.
Elementary particles are divided into two groups: fermions and bosons . If the Standard Model were a high school, fermions would be the students and bosons would be the means by which they communicate.
Beginning with the students, there are two types of fermions: quarks and leptons. In the subatomic classroom, quarks are the outgoing kids always clumped together in “cliques” called hadrons. Opposite to quarks are the leptons, the loners, who prefer to keep to themselves. One particular lepton, the neutrino, rarely ever interacts with any other matter in the universe.
Like people, particles communicate in different ways depending with whom they’re interacting. Bosons, the force-carrying particles of the Standard Model, are like the different forms of communication people use when mingling. Quarks “communicate” using gluons, which would be similar to BFFs texting each other to hang out. Gluons bond quarks together by the strong force. When a lepton gets mixed up in a group of quarks, they interact using photons, which carry the electromagnetic force – like emailing classmates about last week’s homework assignment. Quarks and leptons interact frequently, but they’re not really close.
There is one special type of boson that should be considered its own character in this school: the Higgs, which acts as the foundation for the rest. In physics, the Higgs boson bestows mass to elementary matter particles, preparing them to make up the universe. It’s an extremely special entity because it gives itself mass and even interacts with itself! Think of the Higgs boson as the teacher who imparts knowledge and wisdom through lectures, but also must keep itself informed at the same time. Not every particle has mass, though, and there is still speculation as to whether neutrinos receive their masses from somewhere else. In this school, neutrinos are mysterious rebels who don't listen to their teacher.
The Standard Model, much like high school, doesn’t have all the answers. In a recent study, a team of physicists attempted to solve five important, lingering questions about the Standard Model: what creates the masses for a variety of neutrinos, how is the strong force able to bind quarks in nuclei, what is the origin of dark matter, why is there more matter than antimatter in the universe, and how does inflation work? The team calls this extended theory the Standard Model-Axion-Seesaw-Higgs portal inflation (SMASH), which adds six new particles to the existing list of 17 .
By attempting to unify and explain physics beyond the Standard Model, these physicists show us that there’s more to look forward to beyond the Standard Model high school.
Rashmi Shivni (@rashmishivni)
Guest Contributor, Signal to Noise Magazine
Freelance Science Journalist/Amateur Astronomer
 Ballesteros G, Redondo J, Ringwald A, Tamarit C. (2017). Unifying Inflation with the Axion, Dark Matter, Baryogenesis, and the Seesaw Mechanism. APS Physics. doi: 10.1103/PhysRevLett.118.071802.