Game Of Quarks: A Guide For The Perplexed : 13.7: Cosmos And Culture : NPR
In total, six quarks are enough to explain all hadrons found so far: up,
down, charm, strange, bottom, top. For example, a proton is made of two
up quarks and a down quark. We can represent a proton as (uud). Quarks
are bound together in the proton by particles called gluons (yes, they
glue them together). A neutron is made of the combination (udd). You can
play the same game with the other hadrons, which come in two types:
baryons (three quarks, like proton and neutron) and mesons (made of a
quark and an anti-quark). An anti-quark is like the original quark but
with opposite electric charge.
