APFEL: A PDF evolution library with QED corrections

By Valerio Bertone, Stefano Carrazza, Juan Rojo. Computer Physics Communications, 2013

345 citations recorded by the source corpus.

Abstract Quantum electrodynamics and electroweak corrections are important ingredients for many theoretical predictions at the LHC. This paper documents APFEL , a new PDF evolution package that allows for the first time to perform DGLAP evolution up to NNLO in QCD and to LO in QED, in the variable-flavor-number scheme and with either pole or MS ¯ heavy quark masses. APFEL consistently accounts for the QED corrections to the evolution of quark and gluon PDFs and for the contribution from the photon PDF in the proton. The coupled QCD ⊗ QED equations are solved in x -space by means of higher order interpolation, followed by Runge–Kutta solution of the resulting discretized evolution equations. APFEL is based on an innovative and flexible methodology for the sequential solution of the QCD and QED evolution equations and their combination. In addition to PDF evolution, APFEL provides a module that computes Deep-Inelastic Scattering structure functions in the FONLL general-mass variable-flavor-number scheme up to O ( α s 2 ) . All the functionalities of APFEL can be accessed via a Graphical User Interface, supplemented with a variety of plotting tools for PDFs, parton luminosities and structure functions. Written in Fortran 77, APFEL can also be used via the C/C++ and Python interfaces, and is publicly available from the HepForge repository. Program summary Program title: APFEL Catalogue identifier: AESQ_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AESQ_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 163479 No. of bytes in distributed program, including test data, etc.: 2164619 Distribution format: tar.gz Programming language: Fortran 77, C/C++ and Python. Computer: All. Operating system: All. RAM: ≤ 2 MB Classification: 11.6. External routines: LHAPDF Nature of problem: Solution of the unpolarized coupled DGLAP evolution equations up to NNLO in QCD and to LO in QED in the variable-flavor-number scheme, both with pole and with MSbar masses. Solution method: Representation of parton distributions and splitting functions on a grid in x , discretization of DGLAP evolution equations and higher-order interpolation for general values of x , numerical solution of the resulting discretized evolution equations using Runge–Kutta methods. Restrictions: Smoothness of the initial conditions for the PDF evolution. Running time: A few seconds for initialization, then ∼ 0.5 s for the generation of the PDF tables with combined QCD ⊗ QED evolution (on a Intel(R) Core(TM)2 Duo CPU E6750 @ 2.66 GHz).

Subfields: Artificial Intelligence, Computer Networks and Communications, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/4ce7a0ccd2103518bc19ac517a6b898cab6812e8

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Artificial Intelligence

In Computer Networks and Communications

In Nuclear and High Energy Physics

Citations in the corpus

PDF4LHC recommendations for LHC Run II (2015, methodology): “All the PDFs and luminosity comparison plots shown in this document have been obtained with the APFEL on-line PDF plotting tool [102, 103].”
Parton distributions from high-precision collider data (2017, methodology): “[23], PDF evolution and DIS structure functions are computed using the APFEL public code [99], based instead on the x-space formalism.”
Electroweak radiative corrections for collider physics (2019, background): “QED-corrected PDFs and photon distribution function The inclusion of EW O(α) corrections in the DGLAP evolution has an influence on all PDFs [408–410], but owing to the hierarchy α αs the impact is quite small.”
Parton distributions for the LHC run II (2014, methodology): “0 we use our own internal Mellin-space Fkgenerator code for PDF evolution and DIS observables, but using x-space codes such as HOPPET [142] or APFEL [102] should also be possible.”
The PDF4LHC report on PDFs and LHC data: Results from Run I and preparation for Run II (2015, methodology): “For this purpose, the APFEL-Web online PDF plotting interface [115, 116] has been used.”
Tuning PYTHIA 8.1: the Monash 2013 tune (2014, neutral): “1 LO PDFs with a determination of the photon PDF and a combined QCD+QED evolution [19,71].”
Small-radius jets to all orders in QCD (2014, methodology): “QCDNUM [43], QCD-Pegasus [44], HOPPET [45] or Apfel [46].”
Dynamical scales for multi-TeV top-pair production at the LHC (2016, methodology): “LO, NLO and NNLO partonic cross(7)The plots in figure 11 are prepared with the help of the APFEL library [80]; we thank Juan Rojo for kindly providing us with these plots.”
Illuminating the photon content of the proton within a global PDF analysis (2017, methodology): “This generalisation is made possible thanks to the computation of the splitting functions up to O ( α2 ) and O (ααs) [25, 26], with the resulting QED-corrected evolution equations implemented in public PDF evolution codes such as APFEL [27], HOPPET [28], and QEDEVOL [29].”
The Structure of the Proton in the LHC Precision Era (2017, methodology): “For these calculations, we have used APFEL to produce NNLO(+NLLx) predictions, each using as input the corresponding NNPDF3.”