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arXiv · 2401.05360

Moments of Nucleon Unpolarized, Polarized, and Transversity Parton Distribution Functions from Lattice QCD at the Physical Point

Marcel Rodekamp·Michael Engelhardt·Jeremy R. Green·Stefan Krieg·Simonetta Liuti·Stefan Meinel·John W. Negele·Andrew Pochinsky·Sergey Syritsyn
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Abstract

The second Mellin moments $\langle x\rangle$ of the nucleon's unpolarized, polarized, and transversity parton distribution functions (PDFs) are computed. Two lattice QCD ensembles at the physical pion mass are used: these were generated using a tree-level Symanzik-improved gauge action and 2+1 flavour tree-level improved Wilson Clover fermions coupling via 2-level HEX-smearing. The moments are extracted from forward matrix elements of local leading twist operators. We determine renomalization factors in RI-(S)MOM and match to $\overline{\mathrm{MS}}$ at scale $2\,\mathrm{GeV}$. Our findings show that operators that exhibit vanishing kinematics at zero momentum can have significantly reduced excited-state contamination. The resulting polarized moment is used to quantify the longitudinal contribution to the quark spin-orbit correlation. All our results agree within two sigma with previous lattice results.

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Marcel Rodekamp, Michael Engelhardt, Jeremy R. Green, Stefan Krieg, Simonetta Liuti, Stefan Meinel, John W. Negele, Andrew Pochinsky, Sergey Syritsyn. 2023-12-12. Moments of Nucleon Unpolarized, Polarized, and Transversity Parton Distribution Functions from Lattice QCD at the Physical Point. https://doi.org/10.1103/physrevd.109.074508

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