LHAPDF6: parton density access in the LHC precision era

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

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.

• Item Type: Articles
• Additional Information: AB wishes to acknowledge support from a Royal Society University Research Fellowship, a CERN Scientific Associateship, and IPPP Associateships during the period of LHAPDF 6 development. IPPP grants also supported the work of SL, MR, and David Mallows on this project. KN thanks the University of Glasgow College of Science and Engineering for a PhD studentship scholarship.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Ferrando, Dr James and Buckley, Professor Andy and Nordstrom, Mr Karl
• Authors: Buckley, A., Ferrando, J., Lloyd, S., Nordstrom, K., Page, B., Rüfenacht, M., Schönherr, M., and Watt, G.
• Subjects: Q Science > QC Physics
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: European Physical Journal C
• Journal Abbr.: EPJC
• Publisher: Springer
• ISSN: 1434-6044
• ISSN (Online): 1434-6052
• Copyright Holders: Copyright © 2015 The Authors
• First Published: First published in European Physical Journal C 75:132
• Publisher Policy: Reproduced under a Creative Commons License