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Quark orbital angular momentum from chiral symmetry breaking in QCD

Year: 2026
Type: article
Abstract: The flavor-nonsinglet ( u − d ) quark angular momentum (AM) in the proton is computed based on the effective spin-flavor dynamics emerging from chiral symmetry breaking by QCD instantons. The QCD AM operators are converted to effective spin-flavor operators expressing instanton-induced chiral interactions. A large negative orbital AM L u − d arises from the interactions of the quarks with the chiral mean field in the proton in the large- N c limit. It cancels part of the large positive spin AM S u − d and reduces the total AM J u − d = L u − d + S u − d , in agreement with lattice QCD calculations.
DOI: 10.1016/j.physletb.2026.140980
Institutions: Inha University, Centre National de la Recherche Scientifique, École Polytechnique, Centre de Physique Théorique, Institut Polytechnique de Paris, Thomas Jefferson National Accelerator Facility
Language: English
Open Access status: diamond
Funders: U.S. Department of Energy, Inha University, Ministère de l'Europe et des Affaires Étrangères, Campus France, Ministère de l’Europe et des Affaires étrangères, Office of Science, Nuclear Physics
Awards: G1728142190, G1848180026, G2263355576, G2399599801, G3513891217, G5027663112, G6427981414, G6564173845, G6674091005, G8354049295, G9000372024, G9000373719, G9000379264, G9000385821
OpenAlex ID: W7214012188
FWCI: 1.676
Cites: 32
Cited by: 2
Related to: 10