Elementary Particles

Quarks

Quarks consist of several types of subatomic particles that serve as one of the fundamental constituents of matter. They are associated with one another by way of the strong nuclear force and combine to make up protons and neutrons, just as those particles combine at larger scales to create atomic nuclei. Unlike hadrons (baryons and mesons, described below), quarks do not appear to have their own constituent building blocks - they are seemingly fundamental, and indivisible. They always occur in combinations with other versions or types of the same elemental particle. Quark types are referred to as flavors, and they are divided into three pairs: up versus down; charm versus strange; and top versus bottom.

Flavors of Quark

quark flavor	baryon number	charge	strangeness	charm	bottom	top	mass (MeV)
down (d)	1/3	-(1/3)e	0	0	0	0	5-15
up (u)	1/3	+(2/3)e	0	0	0	0	2-8
strange (s)	1/3	-(1/3)e	-1	0	0	0	100-300
charm (c)	1/3	+(2/3)e	0	1	0	0	1000-1600
bottom (b)	1/3	-(1/3)e	0	0	-1	0	4100-4500
top (t)	1/3	+(2/3)e	0	0	0	1	180000

Hadrons (composite subatomic particles) have two categories based on quark composition: all mesons (electrons, neutrinos, photons, et cetera) consist of a quark and an antiquark in combination, while all baryons (protons, neutrons, et cetera) are composed of three combined quarks.

Bosons

Bosons are particles that mediate fundamental forces in the universe. Unlike fermions, multiple bosons can occupy the same quantum state. There are several types of bosons, each associated with a fundamental force:

• Photons (γ) are responsible for carrying the electromagnetic force, which governs interactions between electrically charged particles. They are massless and travel at the speed of light. Photons transmit (or broadcast the passage of) electromagnetic radiation. The photon is its own antiparticle, because it is electrically neutral.
• Gluons (g) mediate the strong nuclear force, which binds quarks together within hadrons (such as in mesons like protons and neutrons). The SNF is the fundamental force that fuses parts of atomic nuclei together. Gluons carry the color charge of the SNF and come in combinations that are their own antiparticles, as well as combinations that have distinct antiparticles. There are eight types of gluons in quantum chromodynamics (QCD), and their antiparticles are defined by color and anticolor charges.
• Bosons (W+, W-, Z0) are responsible for mediating the weak nuclear force, which governs certain types of particle interactions like radioactive decay. The WNF is involved in processes that change one type of quark into another and is crucial for the energy production of stars. The W+ is the antiparticle of the W− and vice versa; they are charged bosons, and their charge determines the distinction between particle and antiparticle. The Z boson is neutral and is its own antiparticle.
  • Higgs Boson (H0) is associated with the Higgs field, which gives particles mass. Its discovery confirmed the existence of the Higgs mechanism, a fundamental aspect of the Standard Model. The Higgs boson is electrically neutral and has no quantum numbers that would differentiate it from an opposite, so it is considered its own antiparticle.