The Standard Model

The standard model explains all observations so far made by particle physicists. The Standard Model consists of elementary particles grouped into two classes: bosons (particles that transmit forces) and fermions (particles that make up matter). Bosons have particle spin that is either 0, 1 or 2. Fermions have spin 1/2.

Bosons

Name

Spin

Electric
charge

Mass

Observed?

Graviton

2

0

0

Not yet

Photon

1

0

0

Yes

Gluon

1

0

0

Indirectly

W+

1

+1

80 GeV

Yes

W-

1

-1

80 GeV

Yes

Z0

1

0

91 GeV

Yes

Higgs

0

0

> 78 GeV

Not yet


The table above lists the elementary particles in the Standard Model that transmit the four forces observed in Nature, though the gravition is not actually part of the Standard Model.
The evidence for quarks is indirect as they have not been directly observed. They are believed to be confined inside hadrons and unobservable as single particles, except possibly at extremely high temperatures such as could be found very early in the Big Bang.

The fermions in the Standard Model are particles that make up matter, and are grouped into three generations . Notice that the quarks with charge 2/3 come in a group of three, as do the quarks with charge -1/3, as do the electron, muon and tau, and the electron, muon and tau neutrinos. In each group, the heavier particles are shown in the larger type.
It is not yet known why there are three generations of particles that make up matter.

Name

Spin

Electric
charge

Mass

Observed?

Electron

1/2

-1

.0005 GeV

Yes

Muon

1/2

-1

.10 Gev

Yes

Tau

1/2

-1

1.8 Gev

Yes

Name

Spin

Electric
charge

Mass

Observed?

Electron neutrino

1/2

0

0?

Yes

Muon neutrino

1/2

0

<.00017 GeV

Yes

Tau neutrino

1/2

0

<.017 GeV

Yes

Name

Spin

Electric
charge

Mass

Observed?

Up quark

1/2

2/3

.005 GeV

Indirectly

Charm quark

1/2

2/3

1.4 GeV

Indirectly

Top quark

1/2

2/3

174 GeV

Indirectly

Name

Spin

Electric
charge

Mass

Observed?

Down quark

1/2

-1/3

.009 GeV

Indirectly

Strange quark

1/2

-1/3

.17 GeV

Indirectly

Bottom quark

1/2

-1/3

4.4 GeV

Indirectly