xFitter: An Open Source QCD Analysis Framework. A resource and reference document for the Snowmass study

TL;DR

xFitter is an open-source, C++-based software package for QCD analysis, offering versatile tools for precision studies and future facility impact assessments, with ongoing development and broad application in the field.

Contribution

This paper introduces the updated xFitter software (version 2.2.0), highlighting its capabilities, recent analyses, and potential for future precision QCD studies.

Findings

xFitter has been used for diverse analyses including W/Z production and photon PDFs.

The software is modular, flexible, and suitable for impact studies of future facilities.

Ongoing developments aim to enhance precision and extend functionalities.

Abstract

We provide an overview of the xFitter open-source software package, review the general capabilities of the program, and highlight applications relevant to the Snowmass study. An updated version of the program (2.2.0) is available on CERN GitLab, a and this has been updated to a C++ codebase with enhanced and extended features. We also discuss some of the ongoing and future code developments that may be useful for precision studies. We survey recent analyses performed by the xFitter developers' team including: W and Z production, photon PDFs, Drell-Yan forward-backward asymmetry studies, resummation of small-x contributions, heavy quark production, constraints on the strange PDF, determination of the pion PDF, and determination of the pion Fragmentation Functions. Finally, we briefly summarize selected applications of xFitter in the literature. The xFitter program is a versatile, flexible, modular, and comprehensive tool that can provide impact studies for possible future facilities. We encourage the use of xFitter, and welcome new contributions from the community.