How B-mesons are threatening to break the Standard Model | by Ethan Siegel | Starts With A Bang! | Dec, 2024

We have very specific predictions for how particles ought to decay. When we look at B-mesons all together, something vital doesn’t add up.

Most of us, when we think about the Standard Model, think about the fundamental particles and forces that make up the Universe. That’s not a bad thing; that’s largely correct! Within the Standard Model, the prescription for the full suite of particles that ought to exist is:

• six flavors of quarks (up, down, strange, charm, bottom, top),
• three flavors of charged leptons (electron, muon, tau),
• three flavor of uncharged leptons (electron neutrino, muon neutrino, tau neutrino),
• the photon (for the electromagnetic interaction),
• the W-and-Z bosons (for the weak nuclear interaction),
• the gluons (for the strong nuclear interaction),
• and the Higgs boson (the particle associated with the Higgs field).

The quarks and leptons combine together to make the composite structures we’re familiar with, including protons, neutrons, and atoms, while the bosons (all the other particles) mediate the forces between them.