Neutron Valence Structure from Nuclear Deep Inelastic Scattering

Abstract

The partonic structure of the nucleon in the valence region is studied using a global analysis of nuclear deep inelastic scattering (DIS) data on the proton and on nuclei from A = 2 (deuterium) to 208 (lead) to account for the modification of the structure function of nucleons bound in atomic nuclei (i.e. the EMC effect). As compared to previous analyses that only use proton and deuterium data, we find a larger valence down-quark contribution at high-xB. The neutron-to-proton structure function ratio F n 2 /F p 2 is extracted for xB = 0.2−0.9, with an xB → 1 limit of 0.47±0.04, in agreement with predictions such as those of perturbative QCD and Dyson Schwinger equation expectations, but in disagreement with predictions such as the scalar di-quark dominance model. Predictions are also made for F 3 He 2

Selected Science Opportunities for the EicC

“…Evidently, current indications are that the MARATHON data and the reanalysis in Ref. [158] lean heavily in favour of scenario (ii) data on a wide variety of nuclei [158]. This agreement increases confidence in the preliminary MARATHON analysis.…”

“…Theory predictions in both panels: (i) red line and circle at x = 1, the value1 4 , which is obtained if the proton's valence structure is simply u-quark + isoscalar-scalar [ud]-diquark; and (ii) green band, range of values obtained when axial-vector diquark correlations contribute 25-35% of the proton's normalization. Evidently, current indications are that the MARATHON data and the reanalysis in Ref [158]. lean heavily in favour of scenario (ii)…”

Many-body factorization and position–momentum equivalence of nuclear short-range correlations

“…[31] recently claimed a difference between the scaling of SRC pairs with high relative momenta, dominated by pn pairs, and pairs with small separation, having a combinatorial enhancement of pp pairs. This distinction questions the relation between SRC pairs and the modification of the internal structure of nucleons bound in nuclei, extractions of the free neutron structure from nuclear deep inelastic scattering measurements, and the determination of spin-flavor symmetry breaking mecha- nisms in QCD [9]. Our observation that both coordinateand momentum-space contacts exhibit the same scaling show that the speculations of Ref.…”

“…At larger momentum, the fraction of proton-proton (pp) pairs increases, possibly due to their sensitivity to the repulsive core of the nuclear interaction [6,7]. SRCs have significant implications for the internal structure of nucleons bound in nuclei [1,8,9], neutrinoless double beta decay matrix elements [10][11][12], nuclear charge radii [13], and neutron star properties [14,15]. Therefore, understanding their formation mechanisms and specific characteristics is required for obtaining a complete description of atomic nuclei.…”

Nucleon elastic form factors at accessible large spacelike momenta

“…Its location depends on interferences between the various diquark-component contributions to ed scattering within the proton. Thus, like the ratios of valencequark parton distribution functions at large Bjorken x [56,98], the location of the zero in F d…”