This folder ("VetoPrefactors/") which contains the various ingredients
for the resummation using scheme A as described in arXiv:1412.8408
[hep-ph].

The Files AnomalyAndH.f BeamCorr.f and mstwpdf.f contain the
subroutines to each reweighting factor. The Grid files of the PDFs and
beam functions are in the folder Grids. The included beam function
grids were computed with MSTW2008nnlo PDFs; using a different PDF set
will require that the grids are recomputed.

To use:

* Generate a LO event file (but using the NLO process generation),
and unzip it once it is done.

* Make sure to set the ickkw parameter to -1 in the run_card and use
  the MSTW2008nnlo PDF set (lhapdf code is 21200) before the
  generation of the event file.

* Put this folder (as a subfolder of) the Events/run_XXX/ directory.

* Move the virt_reweighter.py and resum_reweighter.py files to the
bin/internal/ directory.

* From the bin/internal/ directory, execute

./virt_reweighter.py ../../Events/run_XXX/events.lhe
./resum_reweighter.py ../../Events/run_XXX/events_rwgt.lhe

and you should get event file with weights that are LO+NNLL(jet-veto)
correct. In the include file JetVetoParameters.inc (which is read in
by resum_driver.f) the reweighting parameters can be changed. They are

   * ptjmax is the value of the jet veto, i.e. the maximum allowed pt
     of jets.

   * MuHScalefactor, MuScalefactor determine the scales in the hard and
     beam functions mu_h=MuHScalefactor*Q, mu=MuScalefactor*ptjmax.  Note
     that MuHScalefactor is a complex variable to allow for mu_h^2 < 0.

   * MuMScalefactor determines the matching scale as
     mu_match=MuMScalefactor*Q.

   * JETRADIUS is the parameter R in the k_T-family jet-algorithms

   * mode: 1=NNLL, 2=NLL, 3=NNLL expanded to NLO, 4=NLL expanded to
     NLO. (Modes 3 and 4 are needed to match to NLO.)

When changing parameters, one only needs to re-run the
resum_reweighter (not the virt_reweighter).