7. Building particles from quarks
The observed particles were either leptons, three quark groupings or quark-antiquark
pairs. Three quark groupings or quark-antiquark pairs are called hadrons.
The hadrons containing three quarks (or three antiquarks) are known as baryons
(baryon means 'heavy')
The hadrons containing quark-antiquark pairs are known as mesons (meson originally
meant medium mass but it was eventually recognised that many mesons have
masses greater than some baryons)
The quark content of some typical baryons and mesons is listed below. It can be
seen that all of the particles can be constructed from the basic quarks and
antiquarks of the quark family.
In some cases it can be see that a particle is seen as a combination of quark
pairs. This way of presenting the combination reflects the mathematical
descriptions of the particles.
Baryons (spin 1/2):
p = uud
n = udd L
= uds S+
= uus S0
= uds S-
= dds X0
= uss X-
= dss L+c
= udc
Baryons (spin 3/2)
D++
= uuu
D+ =
uud, D0
= udd
D- =
ddd S*+
= uus S*0
= uds S*-
= dds X*0
= uss
X*- = dss W- = sss
Pseudoscalar mesons (spin 0)
Vector
mesons (spin 1)
Back to the particle zoo Index
Forward to Feynman vertices
