${{\mathit N}}$ 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 PDGID:
S017

${{\mathit n}}$

$I(J^P)$ = $1/2(1/2^{+})$ 
We have omitted some results that have been superseded by later experiments.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
Expand/Collapse All
${{\mathit n}}$ MASS (atomic mass units u) $1.0086649160$ $\pm0.0000000005$ u 
 
${{\mathit n}}$ MASS (MeV) [1] $939.5654205$ $\pm0.0000005$ MeV 
 
${{\overline{\mathit n}}}$ MASS $939.49$ $\pm0.05$ MeV 
 
(${\mathit m}_{{{\mathit n}}}-{\mathit m}_{{{\overline{\mathit n}}}}$ )/ ${\mathit m}_{{{\mathit n}}}$ ($9$ $\pm5$) $ \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%
 
${{\mathit n}}$ 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
LIMIT ON ${{\mathit n}}{{\mathit n}^{\,'}}$ OSCILLATIONS [2] > 448 s  CL=90%
 
▸  ${{\mathit n}}$ $\rightarrow$ ${{\mathit p}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{{e}}}}$ DECAY PARAMETERS
See the proton listings for many other neutron decay modes.
Mode  
Fraction ($\Gamma_i$ / $\Gamma$) Scale Factor/
Conf. Level		 P(MeV/c)  
$\Gamma_{1}$ ${{\mathit p}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{{e}}}}$ $\sim100$ $\%$ 1
 
$\Gamma_{2}$ ${{\mathit p}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{{e}}}}{{\mathit \gamma}}$ [5] ($9.2$ $\pm0.7$) $ \times 10^{-3}$ 1
 
$\Gamma_{3}$ hydrogen-atom ${{\overline{\mathit \nu}}_{{{e}}}}$ $<2.7$ $\times 10^{-3}$ CL=95% 1
 
▸  Charge conservation (${{\mathit Q}}$) violating mode
▸  Baryon number violating decay
[1] The masses of the ${{\mathit p}}$ and ${{\mathit n}}$ are most precisely known in u (unified atomic mass units). The conversion factor to MeV, 1u = 931.494061(21) MeV, is less well known than are the masses in u.
[2] Lee and Yang in 1956 proposed the existence of a mirror world in an attempt to restore global parity symmetry$-$thus a search for oscillations between the two worlds. Oscillations between the worlds would be maximal when the magnetic fields $\mathit B$ and ${{\mathit B}^{\,'}}$ were equal. The limit for any ${{\mathit B}^{\,'}}$ in the range 0 to 12.5 $\mu $T is $>$12 s (95$\%$ CL).
[3] Time-reversal invariance requires this to be 0$^\circ{}$ or 180$^\circ{}$.
[4] This coefficient is zero if time invariance is not violated.
[5] This limit is for ${{\mathit \gamma}}$ energies between 0.4 and 782 keV.