- baryon number
- a conserved physical quantity that is zero for mesons and leptons and $\pm 1$ for baryons and antibaryons, respectively

- baryons
- hadrons that always decay to another baryon

- boson
- particle with zero or an integer value of intrinsic spin

- bottom
- a quark flavor

- charm
- a quark flavor, which is the counterpart of the strange quark

- colliding beams
- head-on collisions between particles moving in opposite directions

- color
- a quark flavor

- conservation of total baryon number
- a general rule based on the observation that the total number of nucleons was always conserved in nuclear reactions and decays

- conservation of total electron family number
- a general rule stating that the total electron family number stays the same through an interaction

- conservation of total muon family number
- a general rule stating that the total muon family number stays the same through an interaction

- cyclotron
- accelerator that uses fixed-frequency alternating electric fields and fixed magnets to accelerate particles in a circular spiral path

- down
- the second-lightest of all quarks

- electron family number
- the number $\pm 1$ that is assigned to all members of the electron family, or the number 0 that is assigned to all particles not in the electron family

- electroweak theory
- theory showing connections between EM and weak forces

- fermion
- particle with a half-integer value of intrinsic spin

- Feynman diagram
- a graph of time versus position that describes the exchange of virtual particles between subatomic particles

- flavors
- quark type

- fundamental particle
- particle with no substructure

- gauge boson
- particle that carries one of the four forces

- gluons
- eight proposed particles which carry the strong force

- gluons
- exchange particles, analogous to the exchange of photons that gives rise to the electromagnetic force between two charged particles

- grand unified theory
- theory that shows unification of the strong and electroweak forces

- hadrons
- particles that feel the strong nuclear force

- Higgs boson
- a massive particle that, if observed, would give validity to the theory that carrier particles are identical under certain circumstances

- leptons
- particles that do not feel the strong nuclear force

- linear accelerator
- accelerator that accelerates particles in a straight line

- meson
- hadrons that can decay to leptons and leave no hadrons

- meson
- particle whose mass is intermediate between the electron and nucleon masses

- muon family number
- the number $\pm 1$ that is assigned to all members of the muon family, or the number 0 that is assigned to all particles not in the muon family

- particle physics
- the study of and the quest for those truly fundamental particles having no substructure

- pion
- particle exchanged between nucleons, transmitting the force between them

- quantum chromodynamics
- quark theory including color

- quantum chromodynamics
- the governing theory of connecting quantum number color to gluons

- quantum electrodynamics
- the theory of electromagnetism on the particle scale

- quark
- an elementary particle and a fundamental constituent of matter

- standard model
- combination of quantum chromodynamics and electroweak theory

- strange
- the third lightest of all quarks

- strangeness
- a physical quantity assigned to various particles based on decay systematics

- superstring theory
- a theory of everything based on vibrating strings some ${\text{10}}^{-\text{35}}\phantom{\rule{0.25em}{0ex}}\text{m}$ in length

- synchrotron
- a version of a cyclotron in which the frequency of the alternating voltage and the magnetic field strength are increased as the beam particles are accelerated

- synchrotron radiation
- radiation caused by a magnetic field accelerating a charged particle perpendicular to its velocity

- tau family number
- the number $\pm 1$ that is assigned to all members of the tau family, or the number 0 that is assigned to all particles not in the tau family

- theory of quark confinement
- explains how quarks can exist and yet never be isolated or directly observed

- top
- a quark flavor

- up
- the lightest of all quarks

- Van de Graaff
- early accelerator: simple, large-scale version of the electron gun

- virtual particles
- particles which cannot be directly observed but their effects can be directly observed