Valence quark ratio in the proton

TL;DR

This paper uses precise DIS data from helium-3 and tritium to estimate the neutron-to-proton structure function ratio at high x, providing a model-independent prediction for the valence quark ratio in the proton.

Contribution

It introduces a robust, model-independent method to determine the proton's valence-quark ratio at high x using experimental data and nuclear corrections.

Findings

Predicted d_v/u_v ratio at x→1 is approximately 0.23.

Results challenge many existing models of proton structure.

Employs a novel extrapolation technique for structure function ratios.

Abstract

Beginning with precise data on the ratio of structure functions in deep inelastic scattering (DIS) from $^3$He and $^3$H, collected on the domain $0.19 \leq x_B \leq 0.83$, where $x_B$ is the Bjorken scaling variable, we employ a robust method for extrapolating such data to arrive at a model-independent result for the $x_B=1$ value of the ratio of neutron and proton structure functions. Combining this with information obtained in analyses of DIS from nuclei, corrected for target-structure dependence, we arrive at a prediction for the proton's valence-quark ratio: $\left. d_v/u_v \right|_{x_B\to 1} = 0.230 (57)$. Requiring consistency with this result presents a challenge to many descriptions of proton structure.