Boson


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A boson is a fundamental subatomic particle that has integral spin. Examples of bosons include the photon and gluons. Bosons are one of two categories of fundamental subatomic particles, the other being fermions ("matter particles").

The most famous boson is the Higgs boson that is predicted by the Standard Model and gives other particles mass. CERN probably found it in July 2012.

Force mediation
The particles that carry the four fundamental forces of the universe are bosons. Gluons carry the strong nuclear force, for example, and virtual photons carry the electromagnetic force. It is an exchange of these virtual particles, or "gauge bosons", that creates the forces between two non-virtual particles. For example, two negatively-charged electrons repel each other because they are constantly shooting virtual photons at one another; each photon has a little bit of momentum, thus the transfer of photons pushes the electrons around. (This is one of the pillars of quantum electrodynamics; the exchange of gluons within a nucleus forms the basis of quantum chromodynamics.)

Bose-Einstein statistics
Unlike fermions, bosons obey a set of statistics called Bose-Einstein statistics, which were developed in part due to a mistake in applying existing theory by One notable feature is the ability of multiple bosons to occupy the same energy state, giving rise to the phenomenon of Bose-Einstein condensates, of which superfluid helium-4 is probably the best known example. This normal-looking liquid has such fun properties as zero viscosity and the ability to flow over the sides of containers it is placed in.

Known bosons
Photon - The elementary particle which mediates the electromagnetic force. Think of it as a light particle. It couples to (i.e. interacts with) elementary particles with an electric charge but is itself uncharged. It has zero mass.

Gluon - The elementary particle mediating the strong nuclear force. It pretty much glues quarks together to form hadrons like protons and neutrons, and glues protons and neutrons together to form atomic nuclei. While electrically uncharged, it carries color charge, the strong nuclear force analogon to electromagnetic's charge, and interacts with all particles carrying color charge. The gluon, too, is massless.

W±, Z0 - The electrically charged (W) and uncharged (Z) massive elementary particles mediating the weak nuclear force. Popular scientific texts usually shy away from explaining this force while mumbling something about beta decay.

Higgs boson - This particle does not mediate any of the four fundamental forces, but gives other particles mass via the Higgs mechanism. Not to be mixed up with the particle which mediates gravitation, which would be the (hypothetical) graviton - the difference between those two particles is like the difference between mass (property of the object in question) and weight (force felt as a result of the acceleration of a mass due to gravity). It has roughly the mass of an entire caesium atom, but no other charge.