The software behaviour is controlled by two files with steering commands. These files have predefined names:
steering.txt -- controls main "stable" (un-modified during minimisation) parameters. The file also contains names of data files to be fitted to, definition of kinematic cuts
parameters.yaml -- new unified parameter file, to control parameters transfered to the reaction interfaces.
Inclusion of the data files is controlled by &InFiles
namelist in the steering.txt
file. For example, by default the following HERA-II files are included:
&InFiles
NInputFiles = 7
InputFileNames(1) = 'datafiles/hera/h1zeusCombined/inclusiveDis/1506.06042/HERA1+2_NCep_920.dat'
InputFileNames(2) = 'datafiles/hera/h1zeusCombined/inclusiveDis/1506.06042/HERA1+2_NCep_820.dat'
InputFileNames(3) = 'datafiles/hera/h1zeusCombined/inclusiveDis/1506.06042/HERA1+2_NCep_575.dat'
InputFileNames(4) = 'datafiles/hera/h1zeusCombined/inclusiveDis/1506.06042/HERA1+2_NCep_460.dat'
InputFileNames(5) = 'datafiles/hera/h1zeusCombined/inclusiveDis/1506.06042/HERA1+2_NCem.dat'
InputFileNames(6) = 'datafiles/hera/h1zeusCombined/inclusiveDis/1506.06042/HERA1+2_CCep.dat'
InputFileNames(7) = 'datafiles/hera/h1zeusCombined/inclusiveDis/1506.06042/HERA1+2_CCem.dat'
&End
Inclusion of the statistical or systematic correlations of the data in the fit is done via &InCorr
namelist:
&InCorr ! Number of correlation (statistical, systematical or full) files
NCorrFiles = 1
CorrFileNames(1) = 'datafiles/hera/H1_NormInclJets_HighQ2_99-07___H1_NormInclJets_HighQ2_99-07.corr'
&End
in this case the statistical correlations for H1_NormInclJets_HighQ2_99-07 data file are included (the method also allows to include correlations between data sets via file names, i.e: H1_NormInclJets_HighQ2_99-07___H1_InclJets_HighQ2_99-00.dat.corr)
As additional option for data sets with covariance matrix, it is possible to convert covariance matrix to nuisance parameter representation (following the prescription suggested by J. Gao and P. Nadolsky in arXiv:1401.0013):
&CovarToNuisance
! Global switch for using nuisance param representation for covariance mat.
LConvertCovToNui = .true.
! Tolerance -- zero means exact transformation
Tolerance = 0.0
! The following lines allow to adjust error scaling properties
! (default: :M - multiplicative, A - additive)
DataName = 'CMS electon Asymmetry rapidity', 'CMS W muon asymmetry'
DataSystType = ':A', ':A'
&End
The results of the minimization are printed to the standard output and written to the files in the output/
directory (name of the directory can be changed in the steering.txt). The quality of the fit can be judged based on total \chi^2
per degrees of freedom. It is printed for each iteration as
The resulting \chi^2
is reported for each data set and for correlated systematic uncertainties separately. This information is printed and written to the output/Results.txt
file. The Results.txt
file contains additional information about shifts of the correlated systematic uncertainties.
The minimization information from minuit is stored in the output/minuit.out.txt
file. The verboseness level of this information can be changed by minuit commands in the parameters.yaml
file. Make sure that the minuit does not report errors or warnings at the end of minimisation.
Point by point comparison of the data and predictions after the minimization is provided in output/fittedresults.txt
file. The file reports three columns corresponding to three first bins of the input tables, data value, sum in quadrature of statistical and uncorrelated systematic uncertainty, total uncertainty, the predicted value, after applying correlated systematic shifts, pulls between data and theory calculated as (data-theory)/uncorrelated_error, data set index. Similar information is stored in pulls.first.txt
and pulls.last.txt
( dataset index, first bin, second bin, third bin, data, theory, pull), however theory is not adjusted for systematic error shifts in this case.
The output PDFs are stored in forms of tables in output/pdfs_q2val_XX.txt
files. Each of the files reports values of gluon and quark PDFs as a function of x
for fixed Q^2
points. The Q^2
values and x
grid are specified by &Output namelist in the steering.txt
The PDF information and data to theory comparisons can be plotted using the bin/xfitter-draw
program. The program requires the fit output directory as an argument. Calling the program with more directories as arguments provides comparison of the PDFs obtained in the various fits. For a full list of the available options of xfitter-draw please type:
bin/xfitter-draw --help
Finally, the xFitter package provides PDFs in LHAPDF format