LHAPDF6: parton density access in the LHC precision era

Buckley, Andy; Ferrando, James; Lloyd, Stephen; Nordström, Karl; Page, Ben; Rüfenacht, Martin; Schönherr, Marek; Watt, Graeme

Abstract

The Fortran LHAPDF library has been a long-term workhorse in particle physics, providing standardised access to parton density functions for experimental and phenomenological purposes alike, following on from the venerable PDFLIB package. During Run 1 of the LHC, however, several fundamental limitations in LHAPDF’s design have became deeply problematic, restricting the usability of the library for important physics-study procedures and providing dangerous avenues by which to silently obtain incorrect results. In this paper we present the LHAPDF 6 library, a ground-up re-engineering of the PDFLIB/LHAPDF paradigm for PDF access which removes all limits on use of concurrent PDF sets, massively reduces static memory requirements, offers improved CPU performance, and fixes fundamental bugs in multi-set access to PDF metadata. The new design, restricted for now to interpolated PDFs, uses centralised numerical routines and a powerful cascading metadata system to decouple software releases from provision of new PDF data and allow completely general parton content. More than 200 PDF sets have been migrated from LHAPDF 5 to the new universal data format, via a stringent quality control procedure. LHAPDF 6 is supported by many Monte Carlo generators and other physics programs, in some cases via a full set of compatibility routines, and is recommended for the demanding PDF access needs of LHC Run 2 and beyond.

Citation

Buckley, A., Ferrando, J., Lloyd, S., Nordström, K., Page, B., Rüfenacht, M., Schönherr, M., & Watt, G. (2015). LHAPDF6: parton density access in the LHC precision era. The European Physical Journal C, 75(3), Article 132. https://doi.org/10.1140/epjc/s10052-015-3318-8

• Journal Article Type: Article
• Acceptance Date: Feb 10, 2015
• Online Publication Date: Mar 20, 2015
• Publication Date: Mar 31, 2015
• Deposit Date: Mar 15, 2019
• Publicly Available Date: Apr 18, 2019
• Journal: European Physical Journal C: Particles and Fields
• Print ISSN: 1434-6044
• Electronic ISSN: 1434-6052
• Publisher: SpringerOpen
• Peer Reviewed: Peer Reviewed
• Volume: 75
• Issue: 3
• Article Number: 132
• DOI: https://doi.org/10.1140/epjc/s10052-015-3318-8
• Public URL: https://durham-repository.worktribe.com/output/1306121