The antineutron is the

antiparticle In particle physics, every type of particle is associated with an antiparticle with the same mass but with opposite physical charges (such as electric charge). For example, the antiparticle of the electron is the positron (also known as an antie ...

of the neutron with symbol . It differs from the neutron only in that some of its properties have equal magnitude but opposite sign. It has the same mass as the neutron, and no net electric charge, but has opposite

baryon number In particle physics, the baryon number is a strictly conserved additive quantum number of a system. It is defined as ::B = \frac\left(n_\text - n_\bar\right), where ''n''q is the number of quarks, and ''n'' is the number of antiquarks. Baryon ...

(+1 for neutron, −1 for the antineutron). This is because the antineutron is composed of

antiquark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly ...

s, while neutrons are composed of

quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...

s. The antineutron consists of one

up antiquark The up quark or u quark (symbol: u) is the lightest of all quarks, a type of elementary particle, and a significant constituent of matter. It, along with the down quark, forms the neutrons (one up quark, two down quarks) and protons (two up qu ...

and two

down antiquark The down quark or d quark (symbol: d) is the second-lightest of all quarks, a type of elementary particle, and a major constituent of matter. Together with the up quark, it forms the neutrons (one up quark, two down quarks) and protons (two up q ...

Background

The antineutron was discovered in

proton–antiproton collision The antiproton, , (pronounced ''p-bar'') is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy. The exist ...

s at the

Bevatron The Bevatron was a particle accelerator — specifically, a weak-focusing proton synchrotron — at Lawrence Berkeley National Laboratory, U.S., which began operating in 1954. The antiproton was discovered there in 1955, resulting in th ...

( Lawrence Berkeley National Laboratory) by the team of Bruce Cork, Glen Lambertson,

Oreste Piccioni Oreste Piccioni (October 24, 1915 – April 13, 2002) was an Italian-American physicist who made important contributions to elementary particle physics during the early years of its history. He was a graduate student of Enrico Fermi at the U ...

, and William Wenzel in 1956, one year after the

antiproton The antiproton, , (pronounced ''p-bar'') is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy. The exis ...

was discovered. Since the antineutron is electrically neutral, it cannot easily be observed directly. Instead, the products of its

annihilation In particle physics, annihilation is the process that occurs when a subatomic particle collides with its respective antiparticle to produce other particles, such as an electron colliding with a positron to produce two photons. The total ener ...

with ordinary matter are observed. In theory, a free antineutron should decay into an

, a

positron The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. It has an electric charge of +1 '' e'', a spin of 1/2 (the same as the electron), and the same mass as an electron. When a positron collides ...

and a neutrino in a process analogous to the

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For e ...

of free neutrons. There are theoretical proposals of neutron–antineutron oscillations, a process that implies the violation of the

conservation.

Magnetic moment

The magnetic moment of the antineutron is the opposite of that of the neutron. It is for the antineutron but for the neutron (relative to the direction of the

spin Spin or spinning most often refers to: * Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning * Spin, the rotation of an object around a central axis * Spin (propaganda), an intentionally b ...

). Here ''μ''_N is the nuclear magneton.

References

External links

LBL Particle Data Group: summary tables

suppression of neutron-antineutron oscillation

includes information about antineutron discovery (archived link) *

explains how the antineutron differs from the regular neutron despite having the same, that is zero, charge. {{Particles Antimatter Baryons Neutron Nucleons

Background

Magnetic moment

See also

References

External links