Antineutron

The antineutron is the antiparticle of the neutron. It was discovered (in proton-proton collisions in the Bevatron at Berkeley) by Bruce Cork in 1956, a year after the antiproton was discovered. An antineutron has the same mass as a neutron, and no net electric charge. However, it is different from a neutron by being composed of antiquarks, rather than quarks. In particular, the antineutron consists of two anti-down quarks and one anti-up quark.

In theory, an isolated antineutron should decay into an antiproton, a positron and a neutrino, analogously to the decay of the free neutron.

The magnetic moment of the antineutron is the opposite of that of the neutron. It is nowrap|+1.91 µ_N for the antineutron but nowrap|-1.91 µ_N for the neutron (relative to the direction of the spin). Here µ_N is the nuclear magneton.

Since the antineutron is electrically neutral, it cannot easily be observed directly. Instead, the products of its annihilation with ordinary matter are observed.

There are theoretical proposals that neutron-antineutron oscillations exist, a process which would occur only if there is an undiscovered physical process that violates baryon number conservation.

ee also

*list of particles
*antimatter

External links

* [http://pdg.lbl.gov/2005/tables/contents_tables.html LBL Particle Data Group: summary tables]
* [http://arxiv.org/abs/hep-ph/9503300 suppression of neutron-antineutron oscillation]
* [http://science.uwaterloo.ca/~cchieh/cact/nuclear/particles.html Elementary particles] : includes information about antineutron discovery (LINK found BROKEN 20-MAY-2008)
*" [http://www.fnal.gov/pub/inquiring/questions/antineutron.html Is Antineutron the Same as Neutron?] " explains how the antineutron differs from the regular neutron despite having the same, that is zero, charge