Antineutron

Antineutron ( ) ${\displaystyle {\bar {\mathrm {n} }}}$
classification
Fermion Hadron Baryon
properties
electric charge	neutral
Dimensions	1.008 664 915 95 (49)  and
Resting energy	939.565 420 52 (54)  MeV
Spin parity	1/2 -
Isospin	1/2 (z component +1/2)
Interactions	strong weak electromagnetic gravitation
Quark composition	1 anti-up , 2 anti-down

In the standard model, the antineutron is the antiparticle of the neutron . According to the quark model, it consists of two anti-down quarks and one anti-up quark. ${\displaystyle \mathbf {\bar {n}} }$

The antineutron was invented in 1956, one year after the discovery of the antiproton , by Bruce Cork et al. discovered. Like the neutron, it has a mass of around 939.6 MeV / c ² , is electrically uncharged with a spin of ½ and is therefore a fermion . The masses of the neutron and the antineutron are identical with an uncertainty smaller than (9 ± 5) · 10 ⁻⁵ . The CPT theorem predicts certain properties of particles / antiparticles, which can be tested experimentally with the help of the antineutron, for example.

Antineutrons can, for example , be generated during the annihilation of accelerated high-energy electrons and positrons : ${\displaystyle \mathrm {e} ^{+}\mathrm {e} ^{-}\to \mathrm {n} {\bar {\mathrm {n} }}}$

Although the antineutron has the same electrical charge and spin as the neutron, it is a different particle because it is made up of antiquarks. The free antineutron decays into an antiproton, a positron and an electron neutrino , while the free neutron decays into a proton , an electron and an electron antineutrino. The lifetime and the gyromagnetic ratio of the free antineutron have not yet been determined experimentally. According to the CPT theorem, theoretically the lifetimes of and must agree and the gyromagnetic ratio of the antineutron must have the negative value of the gyromagnetic ratio of the neutron. ${\displaystyle \mathbf {n} }$ ${\displaystyle \mathbf {\bar {n}} }$

The experimental search for neutron-antineutron oscillations is viewed as another test of Quark theory. In a vacuum, the free neutron fluctuates to the antineutron with a time constant greater than 2.7 · 10 ⁸ seconds (almost 10 years). Neutron-antineutron oscillations have been proposed theoretically and presuppose an as yet undiscovered process that violates the conservation of baryon numbers.

Individual evidence

1. ↑ CODATA Recommended Values. National Institute of Standards and Technology, accessed July 8, 2019 .  Value for the neutron mass in u . The numbers in brackets denote the uncertainty in the last digits of the value; this uncertainty is given as the estimated standard deviation of the specified numerical value from the actual value.
2. ↑ CODATA Recommended Values. National Institute of Standards and Technology, accessed July 8, 2019 .  Value for the neutron mass in MeV / c ² . The numbers in brackets denote the uncertainty in the last digits of the value; this uncertainty is given as the estimated standard deviation of the specified numerical value from the actual value.
3. ^ DG Phillips II et al. : Neutron-Antineutron Oscillations: Theoretical Status and Experimental Prospects . In: Physics Reports . 612, 2016, pp. 1-45. arxiv : 1410.1100v2 . doi : 10.1016 / j.physrep.2015.11.001 .
4. ^ RN Mohapatra: Neutron-Anti-Neutron Oscillation: Theory and Phenomenology . In: Journal of Physics G . 36, No. 10, 2009, p. 104006. arxiv : 0902.0834 . bibcode : 2009JPhG ... 36j4006M . doi : 10.1088 / 0954-3899 / 36/10/104006 .
5. ^ C. Giunti: Neutron Oscillations . In: Neutrino Unbound . Istituto Nazionale di Fisica Nucleare . August 19, 2010. Archived from the original on September 27, 2011. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved August 19, 2010. 
6. ↑ YA Kamyshkov: Neutron → Antineutron Oscillations . In: NNN 2002 Workshop on "Large Detectors for Proton Decay, Supernovae and Atmospheric Neutrinos and Low Energy Neutrinos from High Intensity Beams" at CERN . January 16, 2002. Retrieved August 19, 2010.

literature

• T. Bressani, A. Filippi: Antineutron physics. In: Physics Reports. 383 (4), 213-297 (2003), doi : 10.1016 / S0370-1573 (03) 00233-3

Web link

Wiktionary: Antineutron  - explanations of meanings, word origins, synonyms, translations