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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

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Andy Buckley

James Ferrando

Stephen Lloyd

Karl Nordström

Ben Page

Martin Rüfenacht


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.


Buckley, A., Ferrando, J., Lloyd, S., Nordström, K., Page, B., Rüfenacht, M., …Watt, G. (2015). LHAPDF6: parton density access in the LHC precision era. The European Physical Journal C, 75(3), Article 132.

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


Published Journal Article (906 Kb)

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Copyright Statement
© The Author(s) 2015.
This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited. Funded by SCOAP3 / License Version CC BY 4.0.

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