Relative difference between up and down quark structure of the proton

TL;DR

This paper introduces a new method to measure the down-to-up quark ratio in the proton using forward-backward asymmetry in LHC collisions, revealing deviations from existing models across a broad momentum range.

Contribution

It presents a novel approach to determine the flavor-specific quark ratio in the proton, providing insights that challenge current parton distribution function predictions.

Findings

Significant deviations from PDF predictions in the down-to-up quark ratio.

Observed x-dependence of the ratio differs from theoretical expectations.

Highlights the need for improved flavor-separated measurements in proton structure studies.

Abstract

We presen a novel determination of the down-to-up composition ratio using the forward-backward asymmetry observed in the proton-proton collisions at the LHC. This method offers unique insights into the flavor-specific difference between down and up quarks, which are difficult to isolate in traditional cross-section measurements due to the inherent mixing of contributions from both flavors. In this study, we systematically measure the down-to-up quark ratio over a broad momentum fraction (x) range of 0.01 to 0.1, utilizing the sensitivity of the forward-backward asymmetry to quark-level couplings. Our findings reveal significant deviations in both the value and x-dependence of this ratio compared to predictions from current parton distribution functions (PDFs). These discrepancies highlight potential limitations in existing PDF parameterization and emphasize the importance of flavor-separated measurements for advancing our understanding of proton structure.