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Baryons consist of 3 valence quarks and
limitless numbers of virtual gluons and quark-antiquark pairs.
Mesons consist of a bound state of a valence quark and
antiquark, plus limitless numbers of virtual gluons and
quark-antiquark pairs. The spin of baryons and mesons is
not intrinsic, but apparently a combination of spins and
orbital angular momenta of the components of the system.
Since the binding energy of hadrons is infinite, there are an
infinite number of different baryons and mesons. Since
almost all baryons and mesons are unstable, the familiar and
fundamental relation ΔE Δt ≃ ℏ means that the unstable
particles do not have definite masses. Such particles are
typically observed as resonances. [See 5.12 in our
textbook.]
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The fundamental vertices of the Standard
Model. See the corresponding Wikipedia entry for an
explanation of some of the notation used in this figure.
Briefly, q is any quark, g
is a gluon, X is any charged particle, γ is a photon,
f is any fermion, m is any particle with mass
(with the possible exception of the neutrinos), mB
is any boson with mass. The Standard Model has 26 parameters
(coupling constants, masses, etc.) but these are not free,
they are fixed by experiment. "Give me six free
parameters and I can fit your grandmother!" -- John
von Neumann.
List of Baryons, List of Mesons.