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Title: Antineutron  
Author: World Heritage Encyclopedia
Language: English
Subject: Antiparticle, Antimatter, Neutron, Neutron magnetic moment, Nucleon
Collection: Antimatter, Baryons, Neutron, Nucleons
Publisher: World Heritage Encyclopedia


The quark structure of the antineutron.
Classification Antibaryon
Composition 1 up antiquark, 2 down antiquarks
Statistics Fermionic
Interactions Strong, Weak, Gravity, Electromagnetic
Status Discovered
Symbol n
Particle Neutron
Discovered Bruce Cork (1956)
Mass 939.565560(81) MeV/c2
Electric charge 0
Magnetic moment +1.91 µN
Spin 12
Isospin 12

The antineutron is the antiparticle of the neutron with symbol n. 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 (+1 for neutron, −1 for the antineutron). This is because the antineutron is composed of antiquarks, while neutrons are composed of quarks. In particular, the antineutron consists of one up antiquark and two down antiquarks.

Since the antineutron is electrically neutral, it cannot easily be observed directly. Instead, the products of its annihilation with ordinary matter are observed. In theory, a free antineutron should decay into an antiproton, a positron and a neutrino in a process analogous to the beta decay of free neutrons. 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.[1][2][3]

The antineutron was discovered in proton–antiproton collisions at the Bevatron (Lawrence Berkeley National Laboratory) by Bruce Cork in 1956, one year after the antiproton was discovered.


  • Magnetic moment 1
  • See also 2
  • References 3
  • External links 4

Magnetic moment

The magnetic moment of the antineutron is the opposite of that of the neutron.[4] It is +1.91 µN for the antineutron but −1.91 µN for the neutron (relative to the direction of the spin). Here µN is the nuclear magneton.

See also


  1. ^ R. N. Mohapatra (2009). "Neutron-Anti-Neutron Oscillation: Theory and Phenomenology".  
  2. ^ C. Giunti, M. Laveder (19 August 2010). "Neutron Oscillations". Neutrino Unbound.  
  3. ^ Y. A. Kamyshkov (16 January 2002). "Neutron → Antineutron Oscillations" (PDF). NNN 2002 Workshop on "Large Detectors for Proton Decay, Supernovae and Atmospheric Neutrinos and Low Energy Neutrinos from High Intensity Beams" at CERN. Retrieved 2010-08-19. 
  4. ^ Lorenzon, Wolfgang (6 April 2007). "Physics 390: Homework set #7 Solutions" (PDF). Modern Physics, Physics 390, Winter 2007. Retrieved 2009-12-22. 

External links

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

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