Neutron valence structure from nuclear deep inelastic scattering

Mechanisms of spin-flavor SU(6) symmetry breaking in quantum chromodynamics (QCD) are studied via an extraction of the free neutron structure function from a global analysis of deep inelastic scattering (DIS) data on the proton and on nuclei from A=2 (deuterium) to 208 (lead). Modification of the structure function of nucleons bound in atomic nuclei (known as the EMC effect) are consistently accounted for within the framework of a universal modification of nucleons in short-range correlated (SRC) pairs. Our extracted neutron-to-proton structure function ratio F[subscript 2 under superscript n]/F[subscript 2 under superscript p] becomes constant for x[subscript B]≥0.6, equaling 0.47±0.04 as x[subscript B]→1, in agreement with theoretical predictions of perturbative QCD and the Dyson-Schwinger equation, and in disagreement with predictions of the scalar diquark dominance model. We also predict [mathematical figure; see resource], recently measured, as yet unpublished, by the MARATHON Collaboration, the nuclear correction function that is needed to extract F[subscript 2 under superscript n]/F[subscript 2 under superscript p] from [mathematical figure; see resource], and the theoretical uncertainty associated with this extraction. ©2020DOE Office of Nuclear Physics (grant no. DE-FG02-94ER40818)DOE Office of Nuclear Physics (grant no. DE-FG02-96ER-40960)DOE Office of Nuclear Physics (grant no. DE-FG02-93ER40771)DOE Office of Nuclear Physics (grant no. DEAC05-06OR23177