Fundamental particles: quarks, hadrons and leptons

Learning objectives

Name the six quark flavours — up, down, strange, charm, top and bottom — recall the charge of each as a fraction of e, and state that every antiquark carries the opposite charge to its quark.

Explain why protons and neutrons are composite rather than fundamental, and give their quark compositions as uud and udd.

Classify a hadron as a baryon (three quarks) or a meson (a quark–antiquark pair), and deduce the charge of any hadron from its quark content.

Describe β⁻ decay as a down quark changing into an up quark and β⁺ decay as an up quark changing into a down quark, and show that charge is conserved in each change.

Identify electrons and neutrinos as leptons, which are fundamental particles, and distinguish leptons from hadrons in particle equations.