Parton Distribution Uncertainties using Smoothness Prior

TL;DR

This paper investigates the uncertainties in proton parton distribution functions at low Bjorken x using HERA data, employing a flexible Chebyshev polynomial parameterization with regularization to reduce uncertainties.

Contribution

It introduces a regularization prior in the parameterization of PDFs, significantly reducing uncertainties at very low x compared to previous methods.

Findings

Accurate determination of gluon density in 0.0005 ≤ x ≤ 0.05 range.

Regularization prior reduces uncertainty for x ≤ 0.0005.

Parameterization uncertainty is small in the studied kinematic range.

Abstract

A study of the parameterization uncertainty at low Bjorken $x \le 0.1$ for the parton distribution functions of the proton is presented. The study is based on the HERA I combined data using a flexible parameterization form based on Chebyshev polynomials with and without an additional regularization constraint. The accuracy of the data allows to determine the gluon density in the kinematic range of $0.0005 \le x \le 0.05 $ with a small parameterization uncertainty. An additional regularization prior leads to a significantly reduced uncertainty for $x \le 0.0005$.