Strange and non-strange distributions from the collider data

TL;DR

This paper evaluates the stability of the ABMP16 parton distribution functions against recent proposed modifications, finding no need for such changes and clarifying the behavior of strange and non-strange quark distributions.

Contribution

It demonstrates that the ABMP16 PDFs are stable and explains the origins of features like strange sea enhancement and the $d/u$ ratio at high x, challenging recent literature suggestions.

Findings

No evidence for strange sea enhancement in ABMP16 PDFs.

The $d/u$ ratio at $x=1$ is consistent with zero after higher-order QCD corrections.

The peculiar features in other analyses are due to shape choices and data interpretation.

Abstract

We check the stability of the ABMP16 fit with respect to modifications of quark PDFs suggested in the recent literature: the strange sea enhancement and a positive non-vanishing $d/u$ ratio at $x \to 1$. These possibilities are examined using test versions of the ABMP16 PDF fit which demonstrate no need of those changes. Furthermore, we localize peculiar features in other analyses which are responsible for a different behaviour of the PDFs obtained. The strange sea enhancement can be explained by a choice of the PDF shapes being not flexible enough and therefore leading to an over-suppressed $d$-quark distribution. This suppression has to be compensated by a corresponding rise by the $s$-quark distribution. As a result, an unusually large strange sea suppression factor is obtained. The non-vanishing value of $d/u\vert _{x=1}$ becomes consistent with zero in case the higher-order QCD corrections to the D{\O} $W$-asymmetry data, which drive its value, are taken into account. Furthermore, the related $e$-asymmetry sample prefers a slightly negative value of $d/u\vert _{x=1}$, although it is consistent with zero. These clarifications support confidence in the PDF shapes used in the ABMP16 analyses.