# Systematic uncertainties in parton distribution functions from lattice QCD simulations at the physical point

## TL;DR

This paper investigates the systematic uncertainties in lattice QCD calculations of nucleon parton distribution functions using the quasi-PDF approach at the physical point, providing detailed analysis and methodology.

## Contribution

It offers a comprehensive analysis of systematic effects in lattice QCD quasi-PDF computations, including renormalization, excited states, and matching procedures.

## Key findings

- Quantified systematic uncertainties in quasi-PDF calculations.
- Analyzed effects of excited states and renormalization schemes.
- Provided guidelines for improving lattice QCD PDF extractions.

## Abstract

We present a detailed study of the helicity-dependent and helicity-independent collinear parton distribution functions (PDFs) of the nucleon, using the quasi-PDF approach. The lattice QCD computation is performed employing twisted mass fermions with a physical value of the light quark mass. We give a systematic and in-depth account of the salient features entering in the evaluation of quasi-PDFs and their relation to the light-cone PDFs. In particular, we give details for the computation of the matrix elements, including the study of the various sources of systematic uncertainties, such as excited states contamination. In addition, we discuss the non-perturbative renormalization scheme used here and its systematics, effects of truncating the Fourier transform and different matching prescriptions.