What does antineutron mean?
The antineutron is the antimatter counterpart of the neutron, one of the particles that make up atomic nuclei. Like the neutron, it carries no electric charge and has virtually the same mass, but it differs fundamentally in composition and properties: it is built from antiquarks instead of quarks, carries a baryon number of −1, and possesses a magnetic moment opposite in sign to that of the neutron. Because it is neutral, an antineutron cannot be detected by the ionization trails that charged particles leave, making it experimentally elusive; physicists typically infer its presence from the telltale burst of energy released when it annihilates on contact with ordinary matter. First observed in the mid-1950s following the discovery of the antiproton, the antineutron remains central to research into antimatter, matter–antimatter asymmetry, and the fundamental symmetries of nature.
nounThe antiparticle of the neutron, having the same mass as a neutron but an equal and opposite magnetic moment and baryon number of −1. An antineutron is electrically neutral, like the neutron, but is composed of antiquarks rather than quarks.
- The antiparticle of the neutron: a neutral baryon made of antiquarks with baryon number −1 and magnetic moment opposite to that of the neutron.
"When an antineutron meets a neutron, the two particles annihilate, releasing energy in the form of other particles."
"Physicists at CERN produced antineutrons in collisions to study how antimatter behaves under gravity."
"An antineutron passing through a detector leaves no ionization trail until it collides with a nucleus and annihilates."
Standard English plural; used when referring to multiple antineutron particles, e.g. in beam or collision experiments.
"The experiment generated beams of antineutrons for studying nucleon–antinucleon interactions."
An antineutron has no electric charge — yet it still annihilates completely when it touches ordinary matter.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of antineutron
The term 'antineutron' was coined in the context of mid-twentieth-century particle physics, after Paul Dirac's theory of antimatter predicted antiparticles for known particles and the antielectron (positron) and antiproton were discovered experimentally. The name combines the prefix 'anti-' (from Greek, meaning 'against' or 'opposite') with 'neutron', itself formed from Latin-derived roots relating to neutrality ('neuter'). The antineutron was first detected experimentally in 1956, shortly after the antiproton's discovery, confirming that even charge-neutral particles have distinct antimatter counterparts.
How antineutron is actually used
Strictly a technical term used in particle physics; rarely encountered outside scientific literature. The word is always singular or plural as a count noun (antineutrons).
Easily confused with antineutron
A neutron is a subatomic particle with no electric charge found in atomic nuclei, whereas an antineutron is its antimatter counterpart with opposite baryon number and magnetic moment.