  We determine within lattice QCD, the nucleon spin carried by valence and sea
quarks, and gluons. The calculation is performed using an ensemble of gauge
configurations with two degenerate light quarks with mass fixed to
approximately reproduce the physical pion mass. We find that the total angular
momentum carried by the quarks in the nucleon is $J_{u+d+s}{=}0.408(61)_{\rm
stat.}(48)_{\rm syst.}$ and the gluon contribution is $J_g {=}0.133(11)_{\rm
stat.}(14)_{\rm syst.}$ giving a total of $J_N{=}0.54(6)_{\rm stat.}(5)_{\rm
syst.}$ consistent with the spin sum. For the quark intrinsic spin contribution
we obtain $\frac{1}{2}\Delta \Sigma_{u+d+s}{=}0.201(17)_{\rm stat.}(5)_{\rm
syst.}$. All quantities are given in the $\overline{\textrm{MS}}$ scheme at
2~GeV. The quark and gluon momentum fractions are also computed and add up to
$\langle x\rangle_{u+d+s}+\langle x\rangle_g{=}0.804(121)_{\rm stat.}(95)_{\rm
syst.}+0.267(12)_{\rm stat.}(10)_{\rm syst.}{=}1.07(12)_{\rm stat.}(10)_{\rm
syst.}$ satisfying the momentum sum.

High Energy Physics - Lattice;High Energy Physics - Experiment;High Energy Physics - Phenomenology;Nuclear Experiment;Nuclear Theory