Components of the Standard Model of Fundamental Particles and Interactions


This is a clickable map; click on it to go directly to the enlargement for any part of the chart.
The "Standard Model" is a term used to describe the quantum theory that includes the theory of strong interactions (quantum chromodynamics or QCD) and the unified theory of weak and electromagnetic interactions (electroweak). Gravity is included on this chart because it is one of the fundamental interactions even though not part of the "Standard Model"

Diagram of Structure within the Atom Larger (115k, gif) Larger (72k, jpg)
The text of the figure reads: If the protons and neutrons in this picture were 10 cm across, then the quarks and electrons would be less than 0.1 mm in size and the entire atom would be about 10 km across.

Spin is the intrinsic angular momentum of particles. Spin is given in units of h-bar, which is the quantum unit of angular momentum, where hbar=h/2pi = 6.58*10^-25 GeV s = 1.05*10^-34 J s.

Electric charges are given in units of the proton's charge. In SI units the electric charge of the proton is 1.60 * 10^-19 coulombs.

The energy unit of particle physics is the electron volt (eV), the energy gained by one electron in crossing a potential difference of one volt. Masses are given in GeV/c^2. (Remember E = mc^2 ), where 1 GeV = 10^9 eV = 1.60 * 10^-10 joule. The mass of the proton is 0.938 GeV/c^2 = 1.67*10^-27 kg

Chart of FERMIONS Larger (78k, gif) Larger (87k, jpg)

Top quark discovered (Fermilab news release)

Chart of BOSONS Larger (66k, gif) Larger (55k, jpg)

Color Charge

Each quark carries one of the three types of "strong charge", also called "color charge". These charges have nothing to do with the colors of visible light. There are eight possible types of color charge for gluons. Just as electrically charged particles interact by exchanging photons, in strong interactions color-charged particles exchange gluons. Leptons, photons, and W and Z bosons have no color charge and hence no strong interaction. One cannot isolate quarks and gluons; they are confined into color-neutral hadrons. This confinement (binding) results from multiple exchanges of gluons among the color-charged objects.

Confinement

As color-charged particles (quarks and gluons ) are separated, the color force between them approaches a constant value and the energy in the color-force field increases. The energy eventually is converted into additional quark-antiquark pairs. The objects that finally emerge are color-neutral combinations called hadrons (mesons and baryons).

Chart of Sample Fermionic Hadrons Larger (29k, gif) Larger (27k, jpg)

Chart of Sample Bosonic Hadrons Larger (32k, gif) Larger (25k, jpg)

Residual Strong Interactions

The strong binding of the color-neutral protons and neutrons to form nuclei is due to residual strong interactions between their color-charged constituents. It is similar to the residual electrical interaction which binds electrically neutral atoms to form molecules. It can be viewed as the exchange of mesons between the hadrons.

Properties of the Interactions

Chart of Properties of the Interactions Larger (52k, gif) Larger (39k, jpg)

Matter and Antimatter

For every particle type there is a corresponding antiparticle type, denoted by a bar over the particle symbol. Particle and antiparticle have identical mass and spin but opposite charges. Some electrically neutral bosons (e.g, Z0, gamma, and eta_c = c cbar but not K0 = ds) are their own antiparticles.

These diagrams are an artist's conception of physical processes. They are not exact and have no meaningful scale. Green shaded areas represent the cloud of gluons or the gluon field, red lines the quark paths, and black lines the paths of leptons.

Charts

Neutron Decay Larger (26k, gif) Larger (19k, jpg)
The text of the figure reads: A neutron decays to a proton, an electron, and an antinuetrino via a virtual (mediating) W boson. This is neutron beta decay.

eplus eminus to Dplus Dminus Larger (29k, gif) Larger (22k, jpg)
The text of the figure reads: An electron and positron (antielectron) colliding at high energy can annihilate to produce D+ and D- mesons via a virtual Z boson or a virtual photon.

eta_c to piplus K0 Kminus Larger (33k, gif) Larger (22k, jpg)
The text of the figure reads: The c and cbar quarks in an eta_c meson annihilate into virtual gluons. Quark pair production in the gluon cloud sometimes gives a pi+, K0, and K- as the final products.

Contemporary Physics Education Project

CPEP is a non-profit organization of teaches, physicists, and educators. For information on the chart, software, book, packet of hands-on classroom activities, and workshops, look on the WWW (URL http://pdg.lbl.gov/cpep.html), send e-mail to pdg@lbl.gov, or write: CPEP, MS 50-308, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. Corporate and private donations, as well as national laboratory funding, have been and remain crucial to the success of this project.

The chart is copyrighted in 1995 by CPEP.

We thank Peter Berglund peter@neuro.hut.fi for taking the time to scan the various components of the Chart, key in the text, and design this layout.

Copyrights and disclaimers and other funding

Betty Armstrong
21-JULY-1995