nucl-th digest · Jun 12, 2017

[Submitted on 9 Jun 2017] (cross-list from hep-lat)

The nucleon spin and momentum decomposition using lattice QCD simulations

C. Alexandrou (Univ. of Cyprus & Cyprus Inst.)🇨🇾 · M. Constantinou (Temple Univ.)🇺🇸 · K. Hadjiyiannakou (Cyprus Inst.)🇨🇾 · K. Jansen (DESY-Zeuthen)🇩🇪 · C. Kallidonis (Cyprus Inst.)🇨🇾 · G. Koutsou (Cyprus Inst.)🇨🇾 · A. Vaquero Avilés-Casco (Univ. of Utah)🇺🇸 · C. Wiese (DESY-Zeuthen)🇩🇪

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 $J_{u + d + s} = 0.408 (61)_{stat.} (48)_{syst.}$ and the gluon contribution is $J_{g} = 0.133 (11)_{stat.} (14)_{syst.}$ giving a total of $J_{N} = 0.54 (6)_{stat.} (5)_{syst.}$ consistent with the spin sum. For the quark intrinsic spin contribution we obtain $\frac{1}{2} Δ Σ_{u + d + s} = 0.201 (17)_{stat.} (5)_{syst.}$ . All quantities are given in the $MS$ scheme at 2~GeV. The quark and gluon momentum fractions are also computed and add up to $⟨ x ⟩_{u + d + s} + ⟨ x ⟩_{g} = 0.804 (121)_{stat.} (95)_{syst.} + 0.267 (12)_{stat.} (10)_{syst.} = 1.07 (12)_{stat.} (10)_{syst.}$ satisfying the momentum sum.

Comments:: Version published in PRL
Subjects:: High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:: 1706.02973 [pdf]

PRL(2017)·172 citations

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The nucleon spin and momentum decomposition using lattice QCD simulations

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