Quarks

Quarks (pronounced “quork” as in pork) are the fundamental particles from which hadrons are made.  They cannot exist on their own.  In baryons they are found as triplets.  In mesons, they are always in a quark-antiquark pair.

There are three main quarks, up, down, and strange.  The names have no real significance beyond the imagination of the physicist that dubbed them such.  They have corresponding antiquarks.  There are three others with even odder names, top (sometimes called "truth"), bottom ("beauty"[!]), and charm, which we won’t worry about here.

Notice how they go in matching pairs.

There are three quantum numbers associated with quarks:

• Charge, expressed as the fraction of the electronic charge.  1/3 e = 5.33 ´ 10^-20 C

• Baryon number

• Strangeness number, when there are strange quarks.

• Each antiquark has equal and opposite values of charge, baryon number and strangeness.

• Baryons are made of three quarks; antibaryons of three antiquarks.

• Mesons are made up of one quark and one antiquark.

• Gluons bind quarks together; they are subject to the strong interaction.

Some mesons such as the neutral Kaon and the neutral Pion (Pi-meson) can be made up in different ways.