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${{\mathit N}}$ BARYONS
($\mathit S$ = 0, $\mathit I$ = 1/2)
${{\mathit p}}$, ${{\mathit N}^{+}}$ = ${\mathit {\mathit u}}$ ${\mathit {\mathit u}}$ ${\mathit {\mathit d}}$; ${{\mathit n}}$, ${{\mathit N}^{0}}$ = ${\mathit {\mathit u}}$ ${\mathit {\mathit d}}$ ${\mathit {\mathit d}}$

INSPIRE JSON (beta) PDGID:

${{\mathit n}}$

$I(J^P)$ = $1/2(1/2^{+})$

We have omitted some results that have been superseded by later experiments. See our earlier editions. Anyone interested in the neutron should look at these two review articles: D. Dubbers and M.G. Schmidt, ``The neutron and its role in cosmology and particle physics,'' Reviews of Modern Physics 83 1111 (2011); and F.E. Wietfeldt and G.L. Greene, ``The neutron lifetime,'' Reviews of Modern Physics 83 1173 (2011).

See related review:

Baryon Decay Parameters

${{\mathit n}}$ MASS (atomic mass units u)

$1.0086649160 \pm0.0000000005$ u

${{\mathit n}}$ MASS (MeV)

$939.5654205 \pm0.0000005$ MeV

${{\overline{\mathit n}}}$ MASS

$939.49 \pm0.05$ MeV

(${\mathit m}_{{{\mathit n}}}–{\mathit m}_{{{\overline{\mathit n}}}}$ )/ ${\mathit m}_{{{\mathit n}}}$

$(9 \pm6) \times 10^{-5}$

${\mathit m}_{{{\mathit n}}}–{\mathit m}_{{{\mathit p}}}$

$1.2933324 \pm0.0000005$ MeV

${{\mathit n}}$ MEAN LIFE

$878.4 \pm0.5$ s (S = 1.8)

${{\mathit n}}$ MAGNETIC MOMENT

$-1.9130427 \pm0.0000005$ $\mu _{\mathit N}$

${{\mathit n}}$ ELECTRIC DIPOLE MOMENT

$<1.8 \times 10^{-26}$ $\mathit e~$cm CL=90.0%

${{\mathit n}}$ MEAN-SQUARE CHARGE RADIUS

$-0.1155 \pm0.0017$ fm${}^{2}$

${{\mathit n}}$ MAGNETIC RADIUS

$0.864 {}^{+0.009}_{-0.008}$ fm

${{\mathit n}}$ ELECTRIC POLARIZABILITY ${{\mathit \alpha}_{{n}}}$

$0.00118 \pm0.00011$ fm${}^{3}$

${{\mathit n}}$ MAGNETIC POLARIZABILITY ${{\mathit \beta}_{{n}}}$

$(3.7 \pm1.2) \times 10^{-4}$ fm${}^{3}$

${{\mathit n}}$ CHARGE

$(-2 \pm8) \times 10^{-22}$ $\mathit e$

LIMIT ON ${{\mathit n}}{{\overline{\mathit n}}}$ OSCILLATIONS

Mean Time for ${{\mathit n}}{{\overline{\mathit n}}}$ Transition

$>8.6 \times 10^{7}$ s CL=90.0%

LIMIT ON ${{\mathit n}}{{\mathit n}^{\,'}}$ OSCILLATIONS

$> 448$ s CL=90.0%

${{\mathit n}}$ $\rightarrow$ ${{\mathit p}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$ DECAY PARAMETERS

$\lambda {}\equiv{\mathit g}_{{{\mathit A}}}$ $/$ ${\mathit g}_{{{\mathit V}}}$

$-1.2754 \pm0.0013$ (S = 2.7)

${{\mathit e}^{-}}$ ASYMMETRY PARAMETER $\mathit A$

$-0.11958 \pm0.00021$ (S = 1.2)

${{\overline{\mathit \nu}}_{{e}}}$ ASYMMETRY PARAMETER $\mathit B$

$0.9807 \pm0.0030$

PROTON ASYMMETRY PARAMETER $\mathit C$

$-0.2377 \pm0.0026$

${{\mathit e}}-{{\overline{\mathit \nu}}_{{e}}}$ ANGULAR CORRELATION COEFFICIENT $\mathit a$

$-0.1049 \pm0.0013$ (S = 1.8)

$\phi _{\mathit AV}$, PHASE OF ${\mathit g}_{{{\mathit A}}}$ RELATIVE TO ${\mathit g}_{{{\mathit V}}}$

$180.017 \pm0.026$ $^\circ{}$

TRIPLE CORRELATION COEFFICIENT $\mathit D$

$(-1.2 \pm2.0) \times 10^{-4}$

TRIPLE CORRELATION COEFFICIENT $\mathit R$

$0.004 \pm0.013$

FIERZ INTERFERENCE TERM $\mathit b$

$0.017 \pm0.020$

${{\mathit n}}$ DECAY MODES ▸ Expand all decays

${{\mathit p}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$

${{\mathit p}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}{{\mathit \gamma}}$

$(9.2\pm{0.7})\times 10^{-3}$

hydrogen-atom ${{\overline{\mathit \nu}}_{{e}}}$

$<2.7\times 10^{-3}$

▸	Charge conservation (${{\mathit Q}}$) violating mode

▸	Baryon number violating decay

FOOTNOTES

Except where otherwise noted, content of the 2023 Review of Particle Physics is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license. The publication of the Review of Particle Physics is supported by US DOE, MEXT (Japan), INFN (Italy), JPS and CERN. Individual collaborators receive support for their PDG activities from their respective institutes or funding agencies. © 2023. See LBNL disclaimers.