Particles
Spin. Spin is a quantum property of
particles. Bosons have integer spin.
Fermions have half-integer spin.
A particle with non-zero spin has
left- or right-handed chirality.
Everything is made of particles.
Symbol
Spin
Electric Charge. Each particle has
positive, negative, or zero electric charge.
Name
(Flavor)
Color Charge. A quark has one of three
color charges called red, green, or blue.
An anti-quark has an anti-color.
A gluon has a color and an anti-color.
u
1⁄
2
⅔
up
___ MeV
Electric
charge
u
u
e−
e+
+
=
Color
charge
Antiparticles. Each particle has
an antiparticle with the same mass
and spin, but opposite charge.
A particle with no charge may be
its own antiparticle.
Mixtures. Some elementary particles
are mixtures (linear superpositions)
of other elementary particles.
?
Mass (electron volts)
Hypothetical. Postulated particles
that many physicists expect will be
discovered.
A particle is a wave in a quantum field.
Elementary Particles
This shows all the elementary particles in the standard model (SM) of particle physics plus some hypothetical particles.
Fermions
Fermions
half-integer spin 1⁄2 3⁄2
Matter is made of fermions.
Fermions obey the exclusion principle.
nucleus
e
u d u u
d
d
proton
uud
d u u d
u
d
neutron
udd
generation
II
⅔
c
⅔
u
up
1⁄
2
charm
d
s
b
-⅓
?
strange
80–130 MeV
4.1–4.4 GeV
e−
μ−
τ−
muon
511 keV
νe
νμ
ντ
electron
neutrino
muon
neutrino
tau
neutrino
Weak force
EW scale
102 GeV
?
Flavor change
radioactivity
Electromagnetic
force
?
<1 eV?
Gravitational
force
G
1
charges attract/repel,
light
creates mass, breaks symmetry
Unified forces split by symmetry breaking.
Other elementary particles may yet be discovered.
Dark matter may be elementary particles not yet discovered.
gluon
1
Weak
Isospin
Wi
W
Composite Particles — Hadrons
W±
Z
W
Z
80 GeV 91 GeV
B
γ
B
photon
Weak
Hypercharge
massless
H
0
Weak
force
massless
0
H
Electromagnetic
force
massless
±
H
Higgs
Higgs field
Higgs
massless
?
Strong
force
g
massless
1
Higgs field(s)
?
<1 eV?
massless
Color force
quarks/gluons attract
Electroweak
1.8 GeV
graviton
Gauge Bosons
Force Carriers
GUT scale
1016 GeV
tau
106 MeV
2
Strong force
?
bottom
4.1-5.7 MeV
masses attract
Grand
Unification
-⅓
spin
Scalar
Bosons
Planck
scale
1019 GeV
-⅓
Bosons
integer spin 0 1 2
Forces are carried by gauge bosons.
Bosons do not obey the exclusion principle.
Gravitational
force
Quantum
Gravity
top
171–175 GeV
<1 eV?
Bosons
⅔
t
1.1–1.4 GeV
electron
1⁄
2
III
1.7–3.1 MeV
down
Leptons
electron
e
Quarks
Atom
I
spin
124-127 GeV
Electroweak symmetry breaking
Light neutral scalar bosons are postulated (for example, axions).
Supersymmetry (SUSY) proposes that every elementary particle has a superpartner.
String theory proposes that all elementary particles are tiny vibrating strings.
Composite particles are composed of two or more elementary particles. This shows some of the hundreds of known composite particles.
Composite Fermions — Baryons
Composite Bosons — Mesons
Baryons are fermions composed of three quarks.
This shows only the baryons made of u, d, and s quarks.
spin 1⁄2 octet
p proton
n neutron
Σ sigma
Λ lambda
Ξ xi
p+ uud
n0 udd
p+
Σ+ uus Σ0 Λ0 uds Σ− dds
Δ++ uuu
spin 3⁄2 decuplet
Δ delta
Σ sigma
Ξ xi
Ω omega-minus
Ξ0 uss
Ξ− dss
Δ+ uud
Δ0 udd
Σ*+ uus
Σ*0 uds
Ξ*0 uss
Ω− sss
Δ− ddd
=
proton
=
neutron
940 MeV
u u
d
uud
938 MeV
n0
Σ*− dds
Ξ*− dss
Mesons are bosons composed of a quark and an antiquark.
This shows only the mesons made of u, d, and s quarks.
u d
d
spin 0 nonet
π pion
η eta
K kaon
K0
π−
nucleons
η′0
K−
spin 1 nonet
ρ rho
ω omega
φ phi
K kaon
K*0
ρ−
ss̄
sū
K0
K*+
ds̄
π+
φ0
K*−
sū
ss̄
K*0
pion
ud̄
sd̄
us̄
ρ0 ω0 uū/dd̄
dū
π0
us̄
π0 η0 uū/dd̄
dū
udd
K+
ds̄
ρ+
135 MeV
=
u ū
uū/dd̄
mixture
Pions carry
the nuclear
force between
nucleons.
ud̄
sd̄
© 2005-2016 Keith Enevoldsen elements.wlonk.com Creative Commons Attribution-ShareAlike 4.0 International License