The antineutron is the antiparticle of the neutron. It was discovered by Bruce Cork in the year 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. Corresponding to each kind of particle, there is an associated antiparticle with the same mass and spin. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... Physicist who discovered the antineutron in 1956. ... 1956 (MCMLVI) was a leap year starting on Sunday of the Gregorian calendar. ... The antiproton (aka pbar) is the antiparticle of the proton. ... Mass is a property of a physical object that quantifies the amount of matter it contains. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interactions. ... Quarks are one of the two basic constituents of matter in the Standard Model of particle physics. ... For other uses of this term, see: Quark (disambiguation) 1974 discovery photograph of a possible charmed baryon, now identified as the Σc++ In particle physics, the quarks are subatomic particles thought to be elemental and indivisible. ... The up quark is a first-generation quark with a charge of +(2/3)e. ...

The magnetic moment of the antineutron is the opposite of that of the neutron. It is +1.91 µ_N for the antineutron but -1.91 µ_N for the neutron (relative to the direction of the spin). Here µ_N is the nuclear magneton. In physics, the magnetic moment or magnetic dipole moment is a measure of the strength of a magnetic source. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is generated by the motion of its center of mass about an external point. ... The nuclear magneton (symbol ), is a physical constant of magnetic moment, defined by: where: is the elementary charge, is the reduced Plancks constant, is the proton rest mass In the SI system of units its value is approximately: = 5. ...

Since the antineutron is electrically neutral, it cannot easily be observed directly. Instead, the products of its annihilation with ordinary matter are observed. Annihilation is defined as total destruction or complete obliteration of a particular object. ...

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

See also

• list of particles
• antimatter

This is a list of particles in particle physics, including currently known and hypothetical elementary particles, as well as the composite particles that can be built up from them. ... Antimatter (or, rarely, contra-terrene matter) is matter that is composed of the antiparticles of those that constitute normal matter. ...

External links

• LBL Particle Data Group - summary tables
• suppression of neutron - antineutron oscillation
• Elementary particles - includes information about antineutron discovery
• Is Antineutron the Same as Neutron? - explains how the antineutron differs from the regular neutron despite having the same, that is zero, charge