Photon

Photon Stats

  • Symbol: γ
  • Type: Gauge Boson
  • Antiparticle: Own
  • Mass: 0
  • Charge: 0
  • Colors: None
  • Lifetime: Stable

The Photon

The photon (symbol: γ) is the force carrier for the electromagnetic force. Unlike fermions, bosons like to be together because they don't follow an exclusion principle; when photons hang out together they hang out in large quantities and make what we call light! Photons allow humans and other organisms to have vision and see colors. They are also what makes photography possible. In addition to light, photons also represent the quantified form of all types of electromagnetic radiation.

The photon is a fundamental gauge boson with integer spin 1; it has no mass and no electric charge, and is its own antiparticle. While the photon mediates the electromagnetic force the particle itself lacks any electric charge, and only experiences one of the four fundamental interactions: gravitation.

One might ask how, if the photon is massless, can it experience the gravitational force—the answer is a little complex in this case, but all particles experience gravitational force to some degree, including the photon—though in the case of the photon, this is only observable over immense distances. A ‘gravitational lens’ is one example of how the gravitational force affects photons— say for example you are observing a distant light source (a far off galaxy), but in between you and that light source there is another galaxy that should be blocking your view of that more distant source. This is not the case that you are observing however, and you can clearly observe the far off galaxy. In this example, because of the immense distance between you and the distant source, gravitational effects on light are observable, and the light actually begins bending (lensing) from the source, as it travels towards the observer (you); so all or part of the light from the distant source actually arches around the obstruction and is able to make its way to your eyes.

History

The modern concept of a photon was developed gradually by Albert Einstein to explain experimental observations that did not fit the classical wave model of light. Many further experiments starting with Compton scattering of single photons by electrons, first observed in 1923, validated Einstein's hypothesis that light itself is quantized. In 1926 the chemist Gilbert N. Lewis coined the name photon for these light particles, and after 1927, when Arthur H. Compton won the Nobel Prize, most scientists accepted the validity of quantified light and the term photon was accepted.

Gluon

Gluon Stats

  • Symbol: g
  • Type: Gauge Boson
  • Antiparticle: 8 gluon colors: 4 particle/antiparticle pairs
  • Mass: 0
  • Charge: 0
  • Colors: 8
  • Lifetime: Stable

The Gluon

The gluon (symbol: g) is the force carrier for the strong force (AKA: color force). In a reaction involving the strong force, there is an exchange of gluons between two color charged particles, such as quarks. Gluons are what bind quarks together to create the protons and neutrons of atomic neuclei; they are the ‘glue’ that keeps all matter together!

The gluon is a fundamental gauge boson with integer spin 1; it has no mass and no electric charge. The gluon both mediates and experiences the strong (color) force; therefore the gluon interacts with two of the four fundamental forces: the strong force, and gravitation. The gluon experiences color charge as it carries the strong force between different colored quarks, binding them together; in doing so it takes on a half and half color mixture based on the quarks it is binding. There are eight gluon color states: red-antigreen, red-antiblue, green-antired, green-antiblue, blue-anti-red, blue-antigreen, and two ‘white’gluons. This may seem counterintuitive- the usual question is: shouldn’t there be nine gluons: red-antigreen, red-antiblue, red-antired, green-antired, green-antiblue, green-antigreen, blue-anti-red, blue-antigreen, blue-antiblue?

Well, red-antired, green-antigreen, and blue-antiblue have no inherent color charge because the combination of opposing color charges cancel each other out to create ‘white’. Because each of those three combinations has no inherent color, those quantum states are allowed to further mix together. In quantum physics, where mixing isn’t forbidden, it happens. So you get another level of combinations of red-antired, green-antigreen, and blue-antiblue states. At this level, three unique mixtures are definable, but one of them becomes truly colorless, and therefore doesn’t physically exist. So you end up with 2 ‘white’ gluons in additon to the other 6 to make a total of 8 kinds.

The antiparticle of any gluon is simply another one of the gluons. For example the antiparticle to the red-antiblue gluon is the blue-antired gluon.

History

Gluons were first discovered in 1979 at the TASSO experiment at the Deutsches Elektronen-Synchrotron (DESY) in Germany. In standard collisions between electrons and positrons (anti-electrons), a quark and antiquark are created, sending off two distinct particle jets which can be observed in the cloud chamber of a particle collider. But at sufficiently high energy, a third jet appears — this third jet is a display of gluons escaping the nucleus. This provided experimental proof for the existence of gluons, whose presence had been already been suspected for some time.

W± and Z0 Bosons

W± and Z0 Stats

  • Symbol: W+, W−, and Z0
  • Type: Gauge Bosons
  • Antiparticle: W±: pair, Z0: own
  • Mass: W±: 80387 MeV/c², Z0: 91188 MeV/c²
  • Charge: W+: +1, W−: −1, Z0: 0
  • Colors: None
  • Lifetime: W± & Z0: 3×10−25 s
  • W± Decays to: lepton + neutrino
    or up-type quark + down-type quark
  • Z0 Decays to: fermion + its antiparticle

The W± and Z0 Bosons

The W and Z bosons (symbols: W± and Z0), together known as the weak bosons, are the carriers of the weak force. In a reaction involving the weak force, there is an exchange of W and/or Z bosons between two particles. This kind of exchange typically happens in instances of radioactive decay or nuclear fusion.

W and Z bosons are massive gauge bosons with integer spin 1. The W+ and W− have electric charges of +1 and -1 respectively, and each have a bare mass of 80387 MeV/c². The Z0 and W− is electrically neutral and has a bare mass of 91188 MeV/c². The W± bosons are an antiparticle pair and the Z is its own antiparticle. All three of these particles are very short-lived with a half-life of about 3×10−25 s. Their discovery was a major success for the Standard Model of particle physics.

While W and Z bosons mediate the weak force, they do not experience this force themselves. The W± bosons experience two of the four fundamental interactions: electromagnetism and gravitation, while the neutral Z0 experiences only gravitation.

History

The discovery of the W and Z bosons was a major success for CERN. 1973 ushered the first observations of neutral current interactions as predicted by electroweak theory. The Gargamelle bubble chamber photographed the tracks of a few electrons suddenly starting to move, seemingly of their own accord. This was interpreted as a neutrino interacting with the electron by the exchange of an unseen Z boson. The neutrino is otherwise undetectable, so the only observable effect is the momentum imparted to the electron by the interaction, thus causing the electrons appearing to move without explanation.

Proof of the W and Z bosons had to wait for the construction of a particle accelerator powerful enough to produce them. This first became possible with the construction of the Super Proton Synchrotron, where W boson signals were seen in January 1983 during a series of experiments made possible by Carlo Rubbia and Simon van der Meer. The experiments were called UA1 (led by Rubbia) and UA2 (led by Pierre Darriulat), and were a collaborative effort by many people. UA1 and UA2 found the Z boson not long after in May 1983. Rubbia and van der Meer were promptly awarded the 1984 Nobel Prize in Physics for these discoveries.

Graviton*

Graviton Stats*

  • Symbol: G
  • Type: Gauge Boson
  • Antiparticle: Own
  • Mass: 0
  • Charge: 0
  • Colors: None
  • Lifetime: Stable

The Graviton

The Graviton (symbol: G) is the theoretical force carrier for the gravitational force. The three other known forces of nature are mediated by elementary particles: electromagnetism by the photon, the strong interaction by the gluons, and the weak interaction by the W and Z bosons. The hypothesis is that the gravitational interaction is likewise mediated by an – as yet undiscovered – elementary particle, dubbed the graviton.

The graviton is expected to be a fundamental gauge boson with integer spin 2; it would have no mass and no electric charge, and would be its own antiparticle. The graviton is theorized to both mediate and experience the gravitational force, one of the four fundamental forces. If it exists, math requires the graviton to be massless and be a spin 2 boson with no net electric charge (electrically neutral). By way of math, it can be shown that any massless spin 2 field would give rise to a force indistinguishable from gravitation, thus indicating that if a massless spin 2 particle is discovered, it must be the graviton.

History

The term “graviton” was introduced in 1934 by Russian physicists Dmitrii Blokhintsev and F. M. Gal'perin in a published article titled “Neutrino Hypothesis and Conservation of Energy.” In 1959, Paul Dirac, announced in an annual lecture that just as James Maxwell’s field theory of electromagnetism predicts the existence of electromagnetic waves, including visible light, as a quantified energy field of photons, Albert Einstein’s general theory of relativity predicts the existence of gravitational waves which, by extension, should also be explained by quantified particles- Dirac also referred to these particles as “gravitons.” This name has since become the term of reference for these hypothetical gravitational force carriers.