nCTEQ is hosted by Hepforge, IPPP Durham

Previous PDF grids & code:


The PDF grids are grouped into families listed below. Every family contains PDF grids for a range of nuclei specified by the number of nucleons (A) and the number of protons (Z). The trailing integers on the grid file names indicate the (A,Z) values computed e.g. a file


belongs to decut3 family and to A=108 and Z=54 (files with A=1,Z=1 correspond to the reference proton fit).
  • decut3
    decut3 is a result of a fit to charged lepton DIS and Drell-Yan data (equivalent to HKN07 data set or to 99% of data set used by EPS09). If you use these grids, please cite reference [1].
  • decut3g1,decut3g2
    decut3gx is a series of families of fits which have their origin in decut3 family but vary the small x behavior of the gluon distribution by changing the assumptions on gluon PDF parametrization. The details are contained in Table 2 of the reference below.
    If you use these grids, please cite references [1,2].
  • decut3,glofac1a
    These families of fits include neutrino DIS data (except decut3) with different weights, ranging from decut3 (w=0) which does not include any neutrino data to nuanua1 (w =infinity) which includes only neutrino DIS data. Intermediate families include both charged lepton and neutrino data with neutrino data having different weight:
    glofac1a (w=1/7), glofac1c (w=1/4),
    glofac1b (w=1/2), global2b (w=1).
    If you use these grids, please cite references [1,3].
  • nutuncor1,nutuncor2
    PDF grids of these families are based also on both charged lepton and neutrino data sets but studying the impact of using uncorrelated errors in neutrino data set. Each family uses uncorrelated errors with neutrino data but the families differ in Q2 cut on DIS data and differ also in assmptions on the gluon PDF:
    nutuncor1 (Q2>4, gluon as in decut3), nutuncor2 (Q2>5, gluon as decut3),
    nutuncor3 (Q2>4, gluon as in decut3g4), nutuncor4 (Q2>5, gluon as in decut3g4).
    If you use these grids, please cite references [1,3].
  1. PDF Nuclear Corrections for Charged and Neutral Current Processes
    I. Schienbein, J.Y. Yu, K. Kovarik, C. Keppel, J.G. Morfin, F. Olness, J.F. Owens, Phys.Rev.D80:094004,2009, arXiv:0907.2357 [hep-ph].
  2. Probing gluon and heavy-quark nuclear PDFs with gamma + Q production in pA collisions.
    T.Stavreva, I. Schienbein, F.Arleo, K. Kovarik, F. Olness, J.Y. Yu, J.F. Owens,
    JHEP 1101 (2011) 152, arXiv:1012.1178 [hep-ph].
  3. Nuclear corrections in neutrino-nucleus DIS and their compatibility with global NPDF analyses
    K. Kovarik, I. Schienbein, F. Olness, J.Y. Yu, C. Keppel, J.G. Morfin, J.F. Owens, T. Stavreva Phys.Rev.Lett.106:122301,2011, arXiv:1012.0286 [hep-ph].


In order to use the grids, you can make use of a sample FORTRAN code which is able to read PDF grids in CTEQ6-CTEQ6.6 format: nCTEQ-code.tar.gz After unpacking the tarball "tar -xzvf nCTEQ-code.tar.gz", one obtains the following files:
Grids/               : directory containing PDF grid files
README.TXT           : short description file
Cteq6Pdf-2008_FIO.f  : CTEQ6 proton evolution code
setNpdf2.f           : code to access the nuclear PDF grids
demo1.f              : demonstration program to show a simple use of provided functions
demo2.f              : program to show the use of functions working with multiple grid files at the same time
pdfNames.f           : list of PDS files and (A,Z) values to be used with demo programs
doit                 : executable Linux scripts to compile demo1.f and demo2.f


Code provides two fundamental functions

SetNPDF(filename,ierr)   - opens and initializes the grid PDS file for reading
                           (filename can contain path if necessary)
CtqNpdf(iparton,x,Q,A,Z) - provides PDF f(x,Q) (not momentum x*PDF !!) for a bound parton
                           specified by iparton = (0,1,2,3,4,5,6) for (g,u,d,s,c,b,t) and
                           corresponding negative values for anti-quark PDF.
                           Values A,Z correspond to the nucleus under consideration where the
                           value A has to correspond to the value in the initialized PDS file
                           (Note: Z should be chosen to correspond to the real nucleus
                           independently of the Z value of the PDS file).

and two additional functions that handle the simultaneous use of two PDF grid files

Set2NPDF(file1,file2,ierr)     - opens and initializes two grid PDS files for reading
                                 (filename can contain path if necessary)
Ctq2Npdf(iset,iparton,x,Q,A,Z) - provides PDF f(x,Q) as CtqNpdf for any of the two initialized
                                 files without the need of repeated opening and initializing the files,
                                 iset = 1,2 correspond to file1 and file2 respectively.

Other Fortran codes:

  • nCTEQ-code.tar.gz (16kB):
    Fortran program to read the PDF grids compatible with CTEQ6-CTEQ6.6 Fortran code.
  • nCTEQ-code-grids.tar.gz (26.7MB):
    Fortran program with a collection of all PDF grids available for a separate download below.
  • nCTEQ-VFNSNF-demo.tar.gz (x.xMB):
    A set of matched VFNS(NF) PDFs (demonstration version)
for comments or requests contact K.Kovarik