ct is hosted by Hepforge, IPPP Durham

 CT18 parton distribution functions


This page provides numerical table files for the computation of CT18 next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) parton distribution functions.  They can be interpolated with the help of a standalone Fortran interface and demonstration program , as well as the tables with interpolated values of the QCD coupling alpha_s and PDFs. A simple C++ interface for the CTEQ-TEA PDFs with CTEQ6.6 or later can be found here.

Parametrizations of CT18 PDFs are also available from the LHAPDF library, version 6. For backward compatibility, we also provide CT18 grids in the LHAPDF5 format. Note that, in order to call all 59 CT18 error PDF sets with LHAPDF 5.9.X, you must recompile LHAPDF with an updated CT wrapper.

ATTENTION: The format of the PDF table files (with the extension .pds) and the Fortran interface were revised in 2012 to provide interpolation of the energy dependence of the QCD running coupling alpha_s using a table of alpha_s values stored inside the .pds file. The pre-2012 PDF table files are partly incompatible with the new format. They can be interpolated by the 2012 interface, but without computing alpha_s.

Available PDF sets

See the header of the Fortran interface for further explanations. 
PDF set Description and links to the table files Authors or main contact References Date Additional resources
CT18 NNLO *General-purpose NNLO central set + 58 eigenvector sets ( LHAPDF6, LHAPDF5 )
*PDF sets with a varied strong coupling alpha_s(M_Z) in the ranges 0.116-0.120 and 0.110-0.124.
The recommended 90% C.L. uncertainty estimate is 0.116 - 0.120.
T.-J. Hou et al.
arXiv:1912.10053 12/2019
Plots of L2 sensitivities
CT18 NLO *General-purpose NLO central set + 58 eigenvector sets ( LHAPDF6, LHAPDF5 )
*PDF sets with a varied strong coupling alpha_s(M_Z) in the ranges 0.116-0.120 and 0.110-0.124.
The recommended 90% C.L. uncertainty estimate is 0.116 - 0.120.
T.-J. Hou et al. arXiv:1912.10053
12/2019

CT18Z NNLO *General-purpose NNLO central set + 58 eigenvector sets ( LHAPDF6, LHAPDF5 )
*PDF sets with a varied strong coupling alpha_s(M_Z) in the ranges 0.116-0.120 and 0.110-0.124.
The recommended 90% C.L. uncertainty estimate is 0.116 - 0.120.
T.-J. Hou et al.
arXiv:1912.10053
12/2019
Plots of L2 sensitivities
CT18Z NLO *General-purpose NLO central set + 58 eigenvector sets ( LHAPDF6, LHAPDF5 )
*PDF sets with a varied strong coupling alpha_s(M_Z) in the ranges 0.116-0.120 and 0.110-0.124.
The recommended 90% C.L. uncertainty estimate is 0.116 - 0.120.
T.-J. Hou et al. arXiv:1912.10053
12/2019

CT18A NNLO *General-purpose NNLO central set + 58 eigenvector sets ( LHAPDF6, LHAPDF5 )
*PDF sets with a varied strong coupling alpha_s(M_Z) in the ranges 0.116-0.120 and 0.110-0.124.
The recommended 90% C.L. uncertainty estimate is 0.116 - 0.120.
T.-J. Hou et al.
arXiv:1912.10053
12/2019
CT18A NLO *General-purpose NLO central set + 58 eigenvector sets ( LHAPDF6, LHAPDF5 )
*PDF sets with a varied strong coupling alpha_s(M_Z) in the ranges 0.116-0.120 and 0.110-0.124.
The recommended 90% C.L. uncertainty estimate is 0.116 - 0.120.
T.-J. Hou et al. arXiv:1912.10053
12/2019

CT18X NNLO *General-purpose NNLO central set + 58 eigenvector sets ( LHAPDF6, LHAPDF5 )
*PDF sets with a varied strong coupling alpha_s(M_Z) in the ranges 0.116-0.120 and 0.110-0.124.
The recommended 90% C.L. uncertainty estimate is 0.116 - 0.120.
T.-J. Hou et al.
arXiv:1912.10053
12/2019
CT18X NLO *General-purpose NLO central set + 58 eigenvector sets ( LHAPDF6, LHAPDF5 )
*PDF sets with a varied strong coupling alpha_s(M_Z) in the ranges 0.116-0.120 and 0.110-0.124.
The recommended 90% C.L. uncertainty estimate is 0.116 - 0.120.
T.-J. Hou et al. arXiv:1912.10053
12/2019

CT18qed (recommended) *General-purpose 1 central + 58 Hessian sets + 2*8 low-Q2 sets (LHAPDF6)
Hessian sets are defined as 90% C.L., and low-Q2 sets are symmetrized and scaled to 90% C.L.
Photon PDF are initialized at mu0=3 GeV (pQCD matching scale) with LUX formula and evolved to higher scales.
K. Xie et al. arXiv:2106.10299
06/2021

CT18qed1(.3)GeV *General-purpose 1 central + 58 Hessian sets + 2*8 low-Q2 sets (LHAPDF6)
Hessian sets are defined as 90% C.L., and low-Q2 sets are symmetrized and scaled to 90% C.L.

Photon PDF are initialized at mu0=1.3 GeV (CT18 PDF starting scale) with LUX formula and evolved to higher scales
K. Xie et al. arXiv:2106.10299
06/2021

CT18lux *General-purpose 1 central + 58 Hessian sets + 2*8 low-Q2 sets (LHAPDF6)
Hessian sets are defined as 90% C.L., and low-Q2 sets are symmetrized and scaled to 90% C.L.

Photon PDF are calculated with the LUX formalism at all scales.
K. Xie et al. arXiv:2106.10299
06/2021


Families of PDFs: CTEQ6-CTEQ6.6, CT10, CT14.
The subtracted PDFs designed for the heavy-flavor hadroproduction can be found in the S-ACOT-MPS project.
Web support:
Tie-Jiun Hou (houtiejiun at mail.neu.edu.cn)
Pavel Nadolsky (nadolsky at smu.edu)
Keping Xie (xiekeping at pitt.edu)
C.-P. Yuan (yuan at pa.msu.edu)

This website is partially supported by the U.S. Department of Energy under Grants DE-SC0010129, DE-FG02-95ER40896 and by the U.S. National Science Foundation under Grants PHY-1719914, PHY-2013791, PHY-1820760, PHY-1820818.