ttbb process at LO/NLO

Asked by Ernesto Arganda on 2017-09-06

Dear MadGraph Team,

We have been trying to reproduce the ttbb process as indicated in Table 5 of your paper arXiv:1405.0301 [hep-ph]. We copy below the run_cardNLOtype.dat file that we have used for running MadGraph5_aMC@NLO (version 2.6.0). We have obtained the following results which are consistent with what you show in your table 5:

--------------------------
NLO-type generation
--------------------------
xs_LO = 6.14 +- 0.07 pb
Scale uncertainty = +62% -35%
PDF uncertainty = +3% -4%

xs_NLO = 15.08 +- 0.44 pb
Scale uncertainty = +38% -28%
PDF uncertainty = +3% -4%

By contrast, if we run MadGraph5 (version 2.6.0) with the run_cardLOtype.dat file (copied below), we obtain this result:

-------------------------
LO-type generation
-------------------------
xs_LO = 1.116 +- 0.008281 pb

We would like to understand why the two calculations at LO show that large differences. Specifically, we would like to ask you some questions:

1.- In order to obtain a cross section at LO, we are inclined to use the last result xs_LO = 1.116 pb. Is this the correct interpretation?

2.- To compute the K-factor we think that one has to compare xs_LO = 6.14 pb with xs_NLO = 15.08 pb, what would mean K=15.08/6.14=2.46. Is that right?

3.- If the result xs_LO = 1.116 pb is the one that we have to use at LO and the K-factor has been well computed in the way of point 2, can we use this K-factor to correct the LO cross section xs_LO = 1.116 pb?

4.- MadGraph5 does not show scale and PDF uncertainties, is there any way to know them?

Thank you very much for your help.

Ernesto Arganda.

-----------------------------------------------
run_cardNLOtype.dat
-----------------------------------------------

#***********************************************************************
# MadGraph5_aMC@NLO *
# *
# run_card.dat aMC@NLO *
# *
# This file is used to set the parameters of the run. *
# *
# Some notation/conventions: *
# *
# Lines starting with a hash (#) are info or comments *
# *
# mind the format: value = variable ! comment *
# *
# Some of the values of variables can be list. These can either be *
# comma or space separated. *
#***********************************************************************
#
#*******************
# Running parameters
#*******************
#
#***********************************************************************
# Tag name for the run (one word) *
#***********************************************************************
  tag_1 = run_tag ! name of the run
#***********************************************************************
# Number of LHE events (and their normalization) and the required *
# (relative) accuracy on the Xsec. *
# These values are ignored for fixed order runs *
#***********************************************************************
 1000 = nevents ! Number of unweighted events requested
 -1.0 = req_acc ! Required accuracy (-1=auto determined from nevents)
 -1 = nevt_job! Max number of events per job in event generation.
                 ! (-1= no split).
#***********************************************************************
# Normalize the weights of LHE events such that they sum or average to *
# the total cross section *
#***********************************************************************
 average = event_norm ! valid settings: average, sum, bias
#***********************************************************************
# Number of points per itegration channel (ignored for aMC@NLO runs) *
#***********************************************************************
 0.1 = req_acc_FO ! Required accuracy (-1=ignored, and use the
                     ! number of points and iter. below)
# These numbers are ignored except if req_acc_FO is equal to -1
 5000 = npoints_FO_grid ! number of points to setup grids
 4 = niters_FO_grid ! number of iter. to setup grids
 10000 = npoints_FO ! number of points to compute Xsec
 6 = niters_FO ! number of iter. to compute Xsec
#***********************************************************************
# Random number seed *
#***********************************************************************
 0 = iseed ! rnd seed (0=assigned automatically=default))
#***********************************************************************
# Collider type and energy *
#***********************************************************************
 1 = lpp1 ! beam 1 type (0 = no PDF)
 1 = lpp2 ! beam 2 type (0 = no PDF)
 6500.0 = ebeam1 ! beam 1 energy in GeV
 6500.0 = ebeam2 ! beam 2 energy in GeV
#***********************************************************************
# PDF choice: this automatically fixes also alpha_s(MZ) and its evol. *
#***********************************************************************
 lhapdf = pdlabel ! PDF set
 23300 = lhaid ! If pdlabel=lhapdf, this is the lhapdf number. Only
              ! numbers for central PDF sets are allowed. Can be a list;
              ! PDF sets beyond the first are included via reweighting.
#***********************************************************************
# Include the NLO Monte Carlo subtr. terms for the following parton *
# shower (HERWIG6 | HERWIGPP | PYTHIA6Q | PYTHIA6PT | PYTHIA8) *
# WARNING: PYTHIA6PT works only for processes without FSR!!!! *
#***********************************************************************
  HERWIG6 = parton_shower
  1.0 = shower_scale_factor ! multiply default shower starting
                                  ! scale by this factor
#***********************************************************************
# Renormalization and factorization scales *
# (Default functional form for the non-fixed scales is the sum of *
# the transverse masses divided by two of all final state particles *
# and partons. This can be changed in SubProcesses/set_scales.f or via *
# dynamical_scale_choice option) *
#***********************************************************************
 False = fixed_ren_scale ! if .true. use fixed ren scale
 False = fixed_fac_scale ! if .true. use fixed fac scale
 91.118 = muR_ref_fixed ! fixed ren reference scale
 91.118 = muF_ref_fixed ! fixed fact reference scale
 -1 = dynamical_scale_choice ! Choose one (or more) of the predefined
           ! dynamical choices. Can be a list; scale choices beyond the
           ! first are included via reweighting
 1.0 = muR_over_ref ! ratio of current muR over reference muR
 1.0 = muF_over_ref ! ratio of current muF over reference muF
#***********************************************************************
# Reweight variables for scale dependence and PDF uncertainty *
#***********************************************************************
 1.0, 2.0, 0.5 = rw_rscale ! muR factors to be included by reweighting
 1.0, 2.0, 0.5 = rw_fscale ! muF factors to be included by reweighting
 True = reweight_scale ! Reweight to get scale variation using the
            ! rw_rscale and rw_fscale factors. Should be a list of
            ! booleans of equal length to dynamical_scale_choice to
            ! specify for which choice to include scale dependence.
 True = reweight_PDF ! Reweight to get PDF uncertainty. Should be a
            ! list booleans of equal length to lhaid to specify for
            ! which PDF set to include the uncertainties.
#***********************************************************************
# Store reweight information in the LHE file for off-line model- *
# parameter reweighting at NLO+PS accuracy *
#***********************************************************************
 False = store_rwgt_info ! Store info for reweighting in LHE file
#***********************************************************************
# ickkw parameter: *
# 0: No merging *
# 3: FxFx Merging - WARNING! Applies merging only at the hard-event *
# level. After showering an MLM-type merging should be applied as *
# well. See http://amcatnlo.cern.ch/FxFx_merging.htm for details. *
# 4: UNLOPS merging (with pythia8 only). No interface from within *
# MG5_aMC available, but available in Pythia8. *
# -1: NNLL+NLO jet-veto computation. See arxiv:1412.8408 [hep-ph]. *
#***********************************************************************
 0 = ickkw
#***********************************************************************
#
#***********************************************************************
# BW cutoff (M+/-bwcutoff*Gamma). Determines which resonances are *
# written in the LHE event file *
#***********************************************************************
 15.0 = bwcutoff
#***********************************************************************
# Cuts on the jets. Jet clustering is performed by FastJet. *
# - When matching to a parton shower, these generation cuts should be *
# considerably softer than the analysis cuts. *
# - More specific cuts can be specified in SubProcesses/cuts.f *
#***********************************************************************
   -1 = jetalgo ! FastJet jet algorithm (1=kT, 0=C/A, -1=anti-kT)
  0.5 = jetradius ! The radius parameter for the jet algorithm
 30.0 = ptj ! Min jet transverse momentum
    4 = etaj ! Max jet abs(pseudo-rap) (a value .lt.0 means no cut)
#***********************************************************************
# Cuts on the charged leptons (e+, e-, mu+, mu-, tau+ and tau-) *
# More specific cuts can be specified in SubProcesses/cuts.f *
#***********************************************************************
  0.0 = ptl ! Min lepton transverse momentum
 -1.0 = etal ! Max lepton abs(pseudo-rap) (a value .lt.0 means no cut)
  0.0 = drll ! Min distance between opposite sign lepton pairs
  0.0 = drll_sf ! Min distance between opp. sign same-flavor lepton pairs
  0.0 = mll ! Min inv. mass of all opposite sign lepton pairs
 30.0 = mll_sf ! Min inv. mass of all opp. sign same-flavor lepton pairs
#***********************************************************************
# Photon-isolation cuts, according to hep-ph/9801442. When ptgmin=0, *
# all the other parameters are ignored. *
# More specific cuts can be specified in SubProcesses/cuts.f *
#***********************************************************************
 20.0 = ptgmin ! Min photon transverse momentum
  2.0 = etagamma ! Max photon abs(pseudo-rap)
  0.7 = R0gamma ! Radius of isolation code
  1.0 = xn ! n parameter of eq.(3.4) in hep-ph/9801442
  1.0 = epsgamma ! epsilon_gamma parameter of eq.(3.4) in hep-ph/9801442
 True = isoEM ! isolate photons from EM energy (photons and leptons)
#***********************************************************************
# For aMCfast+APPLGRID use in PDF fitting (http://amcfast.hepforge.org)*
#***********************************************************************
 0 = iappl ! aMCfast switch (0=OFF, 1=prepare grids, 2=fill grids)
#***********************************************************************

-----------------------------------------------
run_cardLOtype.dat
-----------------------------------------------

#*********************************************************************
# MadGraph5_aMC@NLO *
# *
# run_card.dat MadEvent *
# *
# This file is used to set the parameters of the run. *
# *
# Some notation/conventions: *
# *
# Lines starting with a '# ' are info or comments *
# *
# mind the format: value = variable ! comment *
#*********************************************************************
#
#*******************
# Running parameters
#*******************
#
#*********************************************************************
# Tag name for the run (one word) *
#*********************************************************************
  tag_1 = run_tag ! name of the run
#*********************************************************************
# Number of events and rnd seed *
# Warning: Do not generate more than 1M events in a single run *
# If you want to run Pythia, avoid more than 50k events in a run. *
#*********************************************************************
  1000 = nevents ! Number of unweighted events requested
  0 = iseed ! rnd seed (0=assigned automatically=default))
#*********************************************************************
# Collider type and energy *
# lpp: 0=No PDF, 1=proton, -1=antiproton, 2=photon from proton, *
# 3=photon from electron *
#*********************************************************************
     1 = lpp1 ! beam 1 type
     1 = lpp2 ! beam 2 type
     6500.0 = ebeam1 ! beam 1 total energy in GeV
     6500.0 = ebeam2 ! beam 2 total energy in GeV
#*********************************************************************
# Beam polarization from -100 (left-handed) to 100 (right-handed) *
#*********************************************************************
     0.0 = polbeam1 ! beam polarization for beam 1
     0.0 = polbeam2 ! beam polarization for beam 2
#*********************************************************************
# PDF CHOICE: this automatically fixes also alpha_s and its evol. *
#*********************************************************************
     lhapdf = pdlabel ! PDF set
     23300 = lhaid ! if pdlabel=lhapdf, this is the lhapdf number
#*********************************************************************
# Renormalization and factorization scales *
#*********************************************************************
 False = fixed_ren_scale ! if .true. use fixed ren scale
 False = fixed_fac_scale ! if .true. use fixed fac scale
 91.118 = scale ! fixed ren scale
 91.118 = dsqrt_q2fact1 ! fixed fact scale for pdf1
 91.118 = dsqrt_q2fact2 ! fixed fact scale for pdf2
 3 = dynamical_scale_choice ! Choose one of the preselected dynamical choices
 1.0 = scalefact ! scale factor for event-by-event scales
#*********************************************************************
# Type and output format
#*********************************************************************
  False = gridpack !True = setting up the grid pack
  -1.0 = time_of_flight ! threshold (in mm) below which the invariant livetime is not written (-1 means not written)
  3.0 = lhe_version ! Change the way clustering information pass to shower.
  True = clusinfo ! include clustering tag in output
  average = event_norm ! average/sum. Normalization of the weight in the LHEF

#*********************************************************************
# Matching parameter (MLM only)
#*********************************************************************
 0 = ickkw ! 0 no matching, 1 MLM
 1.0 = alpsfact ! scale factor for QCD emission vx
 False = chcluster ! cluster only according to channel diag
 4 = asrwgtflavor ! highest quark flavor for a_s reweight
 False = auto_ptj_mjj ! Automatic setting of ptj and mjj if xqcut >0
                                   ! (turn off for VBF and single top processes)
 0.0 = xqcut ! minimum kt jet measure between partons
#*********************************************************************
#
#*********************************************************************
# handling of the helicities:
# 0: sum over all helicities
# 1: importance sampling over helicities
#*********************************************************************
   0 = nhel ! using helicities importance sampling or not.
#*********************************************************************
# Generation bias, check the wiki page below for more information: *
# 'cp3.irmp.ucl.ac.be/projects/madgraph/wiki/LOEventGenerationBias' *
#*********************************************************************
 None = bias_module ! Bias type of bias, [None, ptj_bias, -custom_folder-]
 {} = bias_parameters ! Specifies the parameters of the module.
#
#*******************************
# Parton level cuts definition *
#*******************************
#
#
#*********************************************************************
# BW cutoff (M+/-bwcutoff*Gamma) ! Define on/off-shell for "$" and decay
#*********************************************************************
  15.0 = bwcutoff ! (M+/-bwcutoff*Gamma)
#*********************************************************************
# Apply pt/E/eta/dr/mij/kt_durham cuts on decay products or not
# (note that etmiss/ptll/ptheavy/ht/sorted cuts always apply)
#*********************************************************************
   False = cut_decays ! Cut decay products
#*********************************************************************
# Standard Cuts *
#*********************************************************************
# Minimum and maximum pt's (for max, -1 means no cut) *
#*********************************************************************
 30.0 = ptj ! minimum pt for the jets
 30.0 = ptb ! minimum pt for the b
  0.0 = pta ! minimum pt for the photons
 0.0 = ptl ! minimum pt for the charged leptons
 0.0 = misset ! minimum missing Et (sum of neutrino's momenta)
 -1.0 = ptjmax ! maximum pt for the jets
 -1.0 = ptbmax ! maximum pt for the b
 -1.0 = ptamax ! maximum pt for the photons
 -1.0 = ptlmax ! maximum pt for the charged leptons
 -1.0 = missetmax ! maximum missing Et (sum of neutrino's momenta)
#*********************************************************************
# Minimum and maximum E's (in the center of mass frame) *
#*********************************************************************
  0.0 = ej ! minimum E for the jets
  0.0 = eb ! minimum E for the b
  0.0 = ea ! minimum E for the photons
  0.0 = el ! minimum E for the charged leptons
  -1.0 = ejmax ! maximum E for the jets
 -1.0 = ebmax ! maximum E for the b
 -1.0 = eamax ! maximum E for the photons
 -1.0 = elmax ! maximum E for the charged leptons
#*********************************************************************
# Maximum and minimum absolute rapidity (for max, -1 means no cut) *
#*********************************************************************
  4.0 = etaj ! max rap for the jets
  4.0 = etab ! max rap for the b
  2.0 = etaa ! max rap for the photons
 -1.0 = etal ! max rap for the charged leptons
 0.0 = etajmin ! min rap for the jets
 0.0 = etabmin ! min rap for the b
 0.0 = etaamin ! min rap for the photons
 0.0 = etalmin ! main rap for the charged leptons
#*********************************************************************
# Minimum and maximum DeltaR distance *
#*********************************************************************
 0.0 = drjj ! min distance between jets
 0.0 = drbb ! min distance between b's
 0.0 = drll ! min distance between leptons
 0.0 = draa ! min distance between gammas
 0.0 = drbj ! min distance between b and jet
 0.0 = draj ! min distance between gamma and jet
 0.0 = drjl ! min distance between jet and lepton
 0.0 = drab ! min distance between gamma and b
 0.0 = drbl ! min distance between b and lepton
 0.0 = dral ! min distance between gamma and lepton
 -1.0 = drjjmax ! max distance between jets
 -1.0 = drbbmax ! max distance between b's
 -1.0 = drllmax ! max distance between leptons
 -1.0 = draamax ! max distance between gammas
 -1.0 = drbjmax ! max distance between b and jet
 -1.0 = drajmax ! max distance between gamma and jet
 -1.0 = drjlmax ! max distance between jet and lepton
 -1.0 = drabmax ! max distance between gamma and b
 -1.0 = drblmax ! max distance between b and lepton
 -1.0 = dralmax ! maxdistance between gamma and lepton
#*********************************************************************
# Minimum and maximum invariant mass for pairs *
# WARNING: for four lepton final state mmll cut require to have *
# different lepton masses for each flavor! *
#*********************************************************************
 0.0 = mmjj ! min invariant mass of a jet pair
 0.0 = mmbb ! min invariant mass of a b pair
 0.0 = mmaa ! min invariant mass of gamma gamma pair
 0.0 = mmll ! min invariant mass of l+l- (same flavour) lepton pair
 -1.0 = mmjjmax ! max invariant mass of a jet pair
 -1.0 = mmbbmax ! max invariant mass of a b pair
 -1.0 = mmaamax ! max invariant mass of gamma gamma pair
 -1.0 = mmllmax ! max invariant mass of l+l- (same flavour) lepton pair
#*********************************************************************
# Minimum and maximum invariant mass for all letpons *
#*********************************************************************
 0.0 = mmnl ! min invariant mass for all letpons (l+- and vl)
 -1.0 = mmnlmax ! max invariant mass for all letpons (l+- and vl)
#*********************************************************************
# Minimum and maximum pt for 4-momenta sum of leptons *
#*********************************************************************
 0.0 = ptllmin ! Minimum pt for 4-momenta sum of leptons(l and vl)
 -1.0 = ptllmax ! Maximum pt for 4-momenta sum of leptons(l and vl)
#*********************************************************************
# Inclusive cuts *
#*********************************************************************
 0.0 = ptheavy ! minimum pt for at least one heavy final state
 0.0 = xptj ! minimum pt for at least one jet
 0.0 = xptb ! minimum pt for at least one b
 0.0 = xpta ! minimum pt for at least one photon
 0.0 = xptl ! minimum pt for at least one charged lepton
#*********************************************************************
# Control the pt's of the jets sorted by pt *
#*********************************************************************
 0.0 = ptj1min ! minimum pt for the leading jet in pt
 0.0 = ptj2min ! minimum pt for the second jet in pt
 0.0 = ptj3min ! minimum pt for the third jet in pt
 0.0 = ptj4min ! minimum pt for the fourth jet in pt
 -1.0 = ptj1max ! maximum pt for the leading jet in pt
 -1.0 = ptj2max ! maximum pt for the second jet in pt
 -1.0 = ptj3max ! maximum pt for the third jet in pt
 -1.0 = ptj4max ! maximum pt for the fourth jet in pt
 0 = cutuse ! reject event if fails any (0) / all (1) jet pt cuts
#*********************************************************************
# Control the pt's of leptons sorted by pt *
#*********************************************************************
 0.0 = ptl1min ! minimum pt for the leading lepton in pt
 0.0 = ptl2min ! minimum pt for the second lepton in pt
 0.0 = ptl3min ! minimum pt for the third lepton in pt
 0.0 = ptl4min ! minimum pt for the fourth lepton in pt
 -1.0 = ptl1max ! maximum pt for the leading lepton in pt
 -1.0 = ptl2max ! maximum pt for the second lepton in pt
 -1.0 = ptl3max ! maximum pt for the third lepton in pt
 -1.0 = ptl4max ! maximum pt for the fourth lepton in pt
#*********************************************************************
# Control the Ht(k)=Sum of k leading jets *
#*********************************************************************
 0.0 = htjmin ! minimum jet HT=Sum(jet pt)
 -1.0 = htjmax ! maximum jet HT=Sum(jet pt)
 0.0 = ihtmin !inclusive Ht for all partons (including b)
 -1.0 = ihtmax !inclusive Ht for all partons (including b)
 0.0 = ht2min ! minimum Ht for the two leading jets
 0.0 = ht3min ! minimum Ht for the three leading jets
 0.0 = ht4min ! minimum Ht for the four leading jets
 -1.0 = ht2max ! maximum Ht for the two leading jets
 -1.0 = ht3max ! maximum Ht for the three leading jets
 -1.0 = ht4max ! maximum Ht for the four leading jets
#***********************************************************************
# Photon-isolation cuts, according to hep-ph/9801442 *
# When ptgmin=0, all the other parameters are ignored *
# When ptgmin>0, pta and draj are not going to be used *
#***********************************************************************
 20.0 = ptgmin ! Min photon transverse momentum
 0.7 = R0gamma ! Radius of isolation code
 1.0 = xn ! n parameter of eq.(3.4) in hep-ph/9801442
 1.0 = epsgamma ! epsilon_gamma parameter of eq.(3.4) in hep-ph/9801442
 True = isoEM ! isolate photons from EM energy (photons and leptons)
#*********************************************************************
# WBF cuts *
#*********************************************************************
 0.0 = xetamin ! minimum rapidity for two jets in the WBF case
 0.0 = deltaeta ! minimum rapidity for two jets in the WBF case
#***********************************************************************
# Turn on either the ktdurham or ptlund cut to activate *
# CKKW(L) merging with Pythia8 [arXiv:1410.3012, arXiv:1109.4829] *
#***********************************************************************
 -1.0 = ktdurham
 0.5 = dparameter
 -1.0 = ptlund
 1, 2, 3, 4, 5, 6, 21 = pdgs_for_merging_cut ! PDGs for two cuts above
#*********************************************************************
# maximal pdg code for quark to be considered as a light jet *
# (otherwise b cuts are applied) *
#*********************************************************************
 4 = maxjetflavor ! Maximum jet pdg code
#*********************************************************************
#
#*********************************************************************
# Store info for systematics studies *
# WARNING: Do not use for interference type of computation *
#*********************************************************************
   False = use_syst ! Enable systematics studies
#
#**************************************
# Parameter of the systematics study
# will be used by SysCalc (if installed)
#**************************************
#
0.5 1 2 = sys_scalefact # factorization/renormalization scale factor
None = sys_alpsfact # \alpha_s emission scale factors
auto = sys_matchscale # variation of merging scale
# PDF sets and number of members (0 or none for all members).
NNPDF23_lo_as_0130_qed = sys_pdf # list of pdf sets
# MSTW2008nlo68cl.LHgrid 1 = sys_pdf
#

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Ernesto Arganda
Solved:
2017-09-12
Last query:
2017-09-12
Last reply:
2017-09-06

Hi,

> We would like to understand why the two calculations at LO show that large differences

Did you check the cut on the b quark? I believe that you do not have any cut on the pt of the b quark when doing the NLO type of generation (since your b is massive)
And the you have those at LO type of generation (since you specify ptb).

Also you use dynamical_scale_choice -1 which is not the same for LO and NLO type of output. Since you have huge scale uncertainty this can also lead to a significant effect (this is not enough on its own to explain the full difference)

> 1.- In order to obtain a cross section at LO, we are inclined to use the last result xs_LO = 1.116 pb. Is this the correct interpretation?

I do not understand your question here.

> 2.- To compute the K-factor we think that one has to compare xs_LO = 6.14 pb with xs_NLO = 15.08 pb, what would mean K=15.08/6.14=2.46. Is that right?

Yes.

> 3.- If the result xs_LO = 1.116 pb is the one that we have to use at LO and the K-factor has been well computed in the way of point 2, can we use this K-factor to correct the LO cross section xs_LO = 1.116 pb?

Since a K-factor assumes that you have the same enhancement over the full phase-space, the fact that you use it for a more restrictive cut, is not an additional hyppothesis.
So this is kind of ok.

> 4.- MadGraph5 does not show scale and PDF uncertainties, is there any way to know them?

You set in LO run_card use_syst = False
This prevent all the scale/PDF uncertainties computation.

After that you have two possible module to compute the scale/PDF uncertainties from the event generated by MG5aMC.
One C++ module (not developed by us) and one python module.
More detailed here:
https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/Systematics

Cheers,

Olivier

> On 6 Sep 2017, at 22:13, Ernesto Arganda <email address hidden> wrote:
>
> New question #657676 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/657676
>
> Dear MadGraph Team,
>
> We have been trying to reproduce the ttbb process as indicated in Table 5 of your paper arXiv:1405.0301 [hep-ph]. We copy below the run_cardNLOtype.dat file that we have used for running MadGraph5_aMC@NLO (version 2.6.0). We have obtained the following results which are consistent with what you show in your table 5:
>
> --------------------------
> NLO-type generation
> --------------------------
> xs_LO = 6.14 +- 0.07 pb
> Scale uncertainty = +62% -35%
> PDF uncertainty = +3% -4%
>
> xs_NLO = 15.08 +- 0.44 pb
> Scale uncertainty = +38% -28%
> PDF uncertainty = +3% -4%
>
>
> By contrast, if we run MadGraph5 (version 2.6.0) with the run_cardLOtype.dat file (copied below), we obtain this result:
>
> -------------------------
> LO-type generation
> -------------------------
> xs_LO = 1.116 +- 0.008281 pb
>
> We would like to understand why the two calculations at LO show that large differences. Specifically, we would like to ask you some questions:
>
> 1.- In order to obtain a cross section at LO, we are inclined to use the last result xs_LO = 1.116 pb. Is this the correct interpretation?
>
> 2.- To compute the K-factor we think that one has to compare xs_LO = 6.14 pb with xs_NLO = 15.08 pb, what would mean K=15.08/6.14=2.46. Is that right?
>
> 3.- If the result xs_LO = 1.116 pb is the one that we have to use at LO and the K-factor has been well computed in the way of point 2, can we use this K-factor to correct the LO cross section xs_LO = 1.116 pb?
>
> 4.- MadGraph5 does not show scale and PDF uncertainties, is there any way to know them?
>
> Thank you very much for your help.
>
> Ernesto Arganda.
>
>
> -----------------------------------------------
> run_cardNLOtype.dat
> -----------------------------------------------
>
> #***********************************************************************
> # MadGraph5_aMC@NLO *
> # *
> # run_card.dat aMC@NLO *
> # *
> # This file is used to set the parameters of the run. *
> # *
> # Some notation/conventions: *
> # *
> # Lines starting with a hash (#) are info or comments *
> # *
> # mind the format: value = variable ! comment *
> # *
> # Some of the values of variables can be list. These can either be *
> # comma or space separated. *
> #***********************************************************************
> #
> #*******************
> # Running parameters
> #*******************
> #
> #***********************************************************************
> # Tag name for the run (one word) *
> #***********************************************************************
> tag_1 = run_tag ! name of the run
> #***********************************************************************
> # Number of LHE events (and their normalization) and the required *
> # (relative) accuracy on the Xsec. *
> # These values are ignored for fixed order runs *
> #***********************************************************************
> 1000 = nevents ! Number of unweighted events requested
> -1.0 = req_acc ! Required accuracy (-1=auto determined from nevents)
> -1 = nevt_job! Max number of events per job in event generation.
> ! (-1= no split).
> #***********************************************************************
> # Normalize the weights of LHE events such that they sum or average to *
> # the total cross section *
> #***********************************************************************
> average = event_norm ! valid settings: average, sum, bias
> #***********************************************************************
> # Number of points per itegration channel (ignored for aMC@NLO runs) *
> #***********************************************************************
> 0.1 = req_acc_FO ! Required accuracy (-1=ignored, and use the
> ! number of points and iter. below)
> # These numbers are ignored except if req_acc_FO is equal to -1
> 5000 = npoints_FO_grid ! number of points to setup grids
> 4 = niters_FO_grid ! number of iter. to setup grids
> 10000 = npoints_FO ! number of points to compute Xsec
> 6 = niters_FO ! number of iter. to compute Xsec
> #***********************************************************************
> # Random number seed *
> #***********************************************************************
> 0 = iseed ! rnd seed (0=assigned automatically=default))
> #***********************************************************************
> # Collider type and energy *
> #***********************************************************************
> 1 = lpp1 ! beam 1 type (0 = no PDF)
> 1 = lpp2 ! beam 2 type (0 = no PDF)
> 6500.0 = ebeam1 ! beam 1 energy in GeV
> 6500.0 = ebeam2 ! beam 2 energy in GeV
> #***********************************************************************
> # PDF choice: this automatically fixes also alpha_s(MZ) and its evol. *
> #***********************************************************************
> lhapdf = pdlabel ! PDF set
> 23300 = lhaid ! If pdlabel=lhapdf, this is the lhapdf number. Only
> ! numbers for central PDF sets are allowed. Can be a list;
> ! PDF sets beyond the first are included via reweighting.
> #***********************************************************************
> # Include the NLO Monte Carlo subtr. terms for the following parton *
> # shower (HERWIG6 | HERWIGPP | PYTHIA6Q | PYTHIA6PT | PYTHIA8) *
> # WARNING: PYTHIA6PT works only for processes without FSR!!!! *
> #***********************************************************************
> HERWIG6 = parton_shower
> 1.0 = shower_scale_factor ! multiply default shower starting
> ! scale by this factor
> #***********************************************************************
> # Renormalization and factorization scales *
> # (Default functional form for the non-fixed scales is the sum of *
> # the transverse masses divided by two of all final state particles *
> # and partons. This can be changed in SubProcesses/set_scales.f or via *
> # dynamical_scale_choice option) *
> #***********************************************************************
> False = fixed_ren_scale ! if .true. use fixed ren scale
> False = fixed_fac_scale ! if .true. use fixed fac scale
> 91.118 = muR_ref_fixed ! fixed ren reference scale
> 91.118 = muF_ref_fixed ! fixed fact reference scale
> -1 = dynamical_scale_choice ! Choose one (or more) of the predefined
> ! dynamical choices. Can be a list; scale choices beyond the
> ! first are included via reweighting
> 1.0 = muR_over_ref ! ratio of current muR over reference muR
> 1.0 = muF_over_ref ! ratio of current muF over reference muF
> #***********************************************************************
> # Reweight variables for scale dependence and PDF uncertainty *
> #***********************************************************************
> 1.0, 2.0, 0.5 = rw_rscale ! muR factors to be included by reweighting
> 1.0, 2.0, 0.5 = rw_fscale ! muF factors to be included by reweighting
> True = reweight_scale ! Reweight to get scale variation using the
> ! rw_rscale and rw_fscale factors. Should be a list of
> ! booleans of equal length to dynamical_scale_choice to
> ! specify for which choice to include scale dependence.
> True = reweight_PDF ! Reweight to get PDF uncertainty. Should be a
> ! list booleans of equal length to lhaid to specify for
> ! which PDF set to include the uncertainties.
> #***********************************************************************
> # Store reweight information in the LHE file for off-line model- *
> # parameter reweighting at NLO+PS accuracy *
> #***********************************************************************
> False = store_rwgt_info ! Store info for reweighting in LHE file
> #***********************************************************************
> # ickkw parameter: *
> # 0: No merging *
> # 3: FxFx Merging - WARNING! Applies merging only at the hard-event *
> # level. After showering an MLM-type merging should be applied as *
> # well. See http://amcatnlo.cern.ch/FxFx_merging.htm for details. *
> # 4: UNLOPS merging (with pythia8 only). No interface from within *
> # MG5_aMC available, but available in Pythia8. *
> # -1: NNLL+NLO jet-veto computation. See arxiv:1412.8408 [hep-ph]. *
> #***********************************************************************
> 0 = ickkw
> #***********************************************************************
> #
> #***********************************************************************
> # BW cutoff (M+/-bwcutoff*Gamma). Determines which resonances are *
> # written in the LHE event file *
> #***********************************************************************
> 15.0 = bwcutoff
> #***********************************************************************
> # Cuts on the jets. Jet clustering is performed by FastJet. *
> # - When matching to a parton shower, these generation cuts should be *
> # considerably softer than the analysis cuts. *
> # - More specific cuts can be specified in SubProcesses/cuts.f *
> #***********************************************************************
> -1 = jetalgo ! FastJet jet algorithm (1=kT, 0=C/A, -1=anti-kT)
> 0.5 = jetradius ! The radius parameter for the jet algorithm
> 30.0 = ptj ! Min jet transverse momentum
> 4 = etaj ! Max jet abs(pseudo-rap) (a value .lt.0 means no cut)
> #***********************************************************************
> # Cuts on the charged leptons (e+, e-, mu+, mu-, tau+ and tau-) *
> # More specific cuts can be specified in SubProcesses/cuts.f *
> #***********************************************************************
> 0.0 = ptl ! Min lepton transverse momentum
> -1.0 = etal ! Max lepton abs(pseudo-rap) (a value .lt.0 means no cut)
> 0.0 = drll ! Min distance between opposite sign lepton pairs
> 0.0 = drll_sf ! Min distance between opp. sign same-flavor lepton pairs
> 0.0 = mll ! Min inv. mass of all opposite sign lepton pairs
> 30.0 = mll_sf ! Min inv. mass of all opp. sign same-flavor lepton pairs
> #***********************************************************************
> # Photon-isolation cuts, according to hep-ph/9801442. When ptgmin=0, *
> # all the other parameters are ignored. *
> # More specific cuts can be specified in SubProcesses/cuts.f *
> #***********************************************************************
> 20.0 = ptgmin ! Min photon transverse momentum
> 2.0 = etagamma ! Max photon abs(pseudo-rap)
> 0.7 = R0gamma ! Radius of isolation code
> 1.0 = xn ! n parameter of eq.(3.4) in hep-ph/9801442
> 1.0 = epsgamma ! epsilon_gamma parameter of eq.(3.4) in hep-ph/9801442
> True = isoEM ! isolate photons from EM energy (photons and leptons)
> #***********************************************************************
> # For aMCfast+APPLGRID use in PDF fitting (http://amcfast.hepforge.org)*
> #***********************************************************************
> 0 = iappl ! aMCfast switch (0=OFF, 1=prepare grids, 2=fill grids)
> #***********************************************************************
>
> -----------------------------------------------
> run_cardLOtype.dat
> -----------------------------------------------
>
> #*********************************************************************
> # MadGraph5_aMC@NLO *
> # *
> # run_card.dat MadEvent *
> # *
> # This file is used to set the parameters of the run. *
> # *
> # Some notation/conventions: *
> # *
> # Lines starting with a '# ' are info or comments *
> # *
> # mind the format: value = variable ! comment *
> #*********************************************************************
> #
> #*******************
> # Running parameters
> #*******************
> #
> #*********************************************************************
> # Tag name for the run (one word) *
> #*********************************************************************
> tag_1 = run_tag ! name of the run
> #*********************************************************************
> # Number of events and rnd seed *
> # Warning: Do not generate more than 1M events in a single run *
> # If you want to run Pythia, avoid more than 50k events in a run. *
> #*********************************************************************
> 1000 = nevents ! Number of unweighted events requested
> 0 = iseed ! rnd seed (0=assigned automatically=default))
> #*********************************************************************
> # Collider type and energy *
> # lpp: 0=No PDF, 1=proton, -1=antiproton, 2=photon from proton, *
> # 3=photon from electron *
> #*********************************************************************
> 1 = lpp1 ! beam 1 type
> 1 = lpp2 ! beam 2 type
> 6500.0 = ebeam1 ! beam 1 total energy in GeV
> 6500.0 = ebeam2 ! beam 2 total energy in GeV
> #*********************************************************************
> # Beam polarization from -100 (left-handed) to 100 (right-handed) *
> #*********************************************************************
> 0.0 = polbeam1 ! beam polarization for beam 1
> 0.0 = polbeam2 ! beam polarization for beam 2
> #*********************************************************************
> # PDF CHOICE: this automatically fixes also alpha_s and its evol. *
> #*********************************************************************
> lhapdf = pdlabel ! PDF set
> 23300 = lhaid ! if pdlabel=lhapdf, this is the lhapdf number
> #*********************************************************************
> # Renormalization and factorization scales *
> #*********************************************************************
> False = fixed_ren_scale ! if .true. use fixed ren scale
> False = fixed_fac_scale ! if .true. use fixed fac scale
> 91.118 = scale ! fixed ren scale
> 91.118 = dsqrt_q2fact1 ! fixed fact scale for pdf1
> 91.118 = dsqrt_q2fact2 ! fixed fact scale for pdf2
> 3 = dynamical_scale_choice ! Choose one of the preselected dynamical choices
> 1.0 = scalefact ! scale factor for event-by-event scales
> #*********************************************************************
> # Type and output format
> #*********************************************************************
> False = gridpack !True = setting up the grid pack
> -1.0 = time_of_flight ! threshold (in mm) below which the invariant livetime is not written (-1 means not written)
> 3.0 = lhe_version ! Change the way clustering information pass to shower.
> True = clusinfo ! include clustering tag in output
> average = event_norm ! average/sum. Normalization of the weight in the LHEF
>
> #*********************************************************************
> # Matching parameter (MLM only)
> #*********************************************************************
> 0 = ickkw ! 0 no matching, 1 MLM
> 1.0 = alpsfact ! scale factor for QCD emission vx
> False = chcluster ! cluster only according to channel diag
> 4 = asrwgtflavor ! highest quark flavor for a_s reweight
> False = auto_ptj_mjj ! Automatic setting of ptj and mjj if xqcut >0
> ! (turn off for VBF and single top processes)
> 0.0 = xqcut ! minimum kt jet measure between partons
> #*********************************************************************
> #
> #*********************************************************************
> # handling of the helicities:
> # 0: sum over all helicities
> # 1: importance sampling over helicities
> #*********************************************************************
> 0 = nhel ! using helicities importance sampling or not.
> #*********************************************************************
> # Generation bias, check the wiki page below for more information: *
> # 'cp3.irmp.ucl.ac.be/projects/madgraph/wiki/LOEventGenerationBias' *
> #*********************************************************************
> None = bias_module ! Bias type of bias, [None, ptj_bias, -custom_folder-]
> {} = bias_parameters ! Specifies the parameters of the module.
> #
> #*******************************
> # Parton level cuts definition *
> #*******************************
> #
> #
> #*********************************************************************
> # BW cutoff (M+/-bwcutoff*Gamma) ! Define on/off-shell for "$" and decay
> #*********************************************************************
> 15.0 = bwcutoff ! (M+/-bwcutoff*Gamma)
> #*********************************************************************
> # Apply pt/E/eta/dr/mij/kt_durham cuts on decay products or not
> # (note that etmiss/ptll/ptheavy/ht/sorted cuts always apply)
> #*********************************************************************
> False = cut_decays ! Cut decay products
> #*********************************************************************
> # Standard Cuts *
> #*********************************************************************
> # Minimum and maximum pt's (for max, -1 means no cut) *
> #*********************************************************************
> 30.0 = ptj ! minimum pt for the jets
> 30.0 = ptb ! minimum pt for the b
> 0.0 = pta ! minimum pt for the photons
> 0.0 = ptl ! minimum pt for the charged leptons
> 0.0 = misset ! minimum missing Et (sum of neutrino's momenta)
> -1.0 = ptjmax ! maximum pt for the jets
> -1.0 = ptbmax ! maximum pt for the b
> -1.0 = ptamax ! maximum pt for the photons
> -1.0 = ptlmax ! maximum pt for the charged leptons
> -1.0 = missetmax ! maximum missing Et (sum of neutrino's momenta)
> #*********************************************************************
> # Minimum and maximum E's (in the center of mass frame) *
> #*********************************************************************
> 0.0 = ej ! minimum E for the jets
> 0.0 = eb ! minimum E for the b
> 0.0 = ea ! minimum E for the photons
> 0.0 = el ! minimum E for the charged leptons
> -1.0 = ejmax ! maximum E for the jets
> -1.0 = ebmax ! maximum E for the b
> -1.0 = eamax ! maximum E for the photons
> -1.0 = elmax ! maximum E for the charged leptons
> #*********************************************************************
> # Maximum and minimum absolute rapidity (for max, -1 means no cut) *
> #*********************************************************************
> 4.0 = etaj ! max rap for the jets
> 4.0 = etab ! max rap for the b
> 2.0 = etaa ! max rap for the photons
> -1.0 = etal ! max rap for the charged leptons
> 0.0 = etajmin ! min rap for the jets
> 0.0 = etabmin ! min rap for the b
> 0.0 = etaamin ! min rap for the photons
> 0.0 = etalmin ! main rap for the charged leptons
> #*********************************************************************
> # Minimum and maximum DeltaR distance *
> #*********************************************************************
> 0.0 = drjj ! min distance between jets
> 0.0 = drbb ! min distance between b's
> 0.0 = drll ! min distance between leptons
> 0.0 = draa ! min distance between gammas
> 0.0 = drbj ! min distance between b and jet
> 0.0 = draj ! min distance between gamma and jet
> 0.0 = drjl ! min distance between jet and lepton
> 0.0 = drab ! min distance between gamma and b
> 0.0 = drbl ! min distance between b and lepton
> 0.0 = dral ! min distance between gamma and lepton
> -1.0 = drjjmax ! max distance between jets
> -1.0 = drbbmax ! max distance between b's
> -1.0 = drllmax ! max distance between leptons
> -1.0 = draamax ! max distance between gammas
> -1.0 = drbjmax ! max distance between b and jet
> -1.0 = drajmax ! max distance between gamma and jet
> -1.0 = drjlmax ! max distance between jet and lepton
> -1.0 = drabmax ! max distance between gamma and b
> -1.0 = drblmax ! max distance between b and lepton
> -1.0 = dralmax ! maxdistance between gamma and lepton
> #*********************************************************************
> # Minimum and maximum invariant mass for pairs *
> # WARNING: for four lepton final state mmll cut require to have *
> # different lepton masses for each flavor! *
> #*********************************************************************
> 0.0 = mmjj ! min invariant mass of a jet pair
> 0.0 = mmbb ! min invariant mass of a b pair
> 0.0 = mmaa ! min invariant mass of gamma gamma pair
> 0.0 = mmll ! min invariant mass of l+l- (same flavour) lepton pair
> -1.0 = mmjjmax ! max invariant mass of a jet pair
> -1.0 = mmbbmax ! max invariant mass of a b pair
> -1.0 = mmaamax ! max invariant mass of gamma gamma pair
> -1.0 = mmllmax ! max invariant mass of l+l- (same flavour) lepton pair
> #*********************************************************************
> # Minimum and maximum invariant mass for all letpons *
> #*********************************************************************
> 0.0 = mmnl ! min invariant mass for all letpons (l+- and vl)
> -1.0 = mmnlmax ! max invariant mass for all letpons (l+- and vl)
> #*********************************************************************
> # Minimum and maximum pt for 4-momenta sum of leptons *
> #*********************************************************************
> 0.0 = ptllmin ! Minimum pt for 4-momenta sum of leptons(l and vl)
> -1.0 = ptllmax ! Maximum pt for 4-momenta sum of leptons(l and vl)
> #*********************************************************************
> # Inclusive cuts *
> #*********************************************************************
> 0.0 = ptheavy ! minimum pt for at least one heavy final state
> 0.0 = xptj ! minimum pt for at least one jet
> 0.0 = xptb ! minimum pt for at least one b
> 0.0 = xpta ! minimum pt for at least one photon
> 0.0 = xptl ! minimum pt for at least one charged lepton
> #*********************************************************************
> # Control the pt's of the jets sorted by pt *
> #*********************************************************************
> 0.0 = ptj1min ! minimum pt for the leading jet in pt
> 0.0 = ptj2min ! minimum pt for the second jet in pt
> 0.0 = ptj3min ! minimum pt for the third jet in pt
> 0.0 = ptj4min ! minimum pt for the fourth jet in pt
> -1.0 = ptj1max ! maximum pt for the leading jet in pt
> -1.0 = ptj2max ! maximum pt for the second jet in pt
> -1.0 = ptj3max ! maximum pt for the third jet in pt
> -1.0 = ptj4max ! maximum pt for the fourth jet in pt
> 0 = cutuse ! reject event if fails any (0) / all (1) jet pt cuts
> #*********************************************************************
> # Control the pt's of leptons sorted by pt *
> #*********************************************************************
> 0.0 = ptl1min ! minimum pt for the leading lepton in pt
> 0.0 = ptl2min ! minimum pt for the second lepton in pt
> 0.0 = ptl3min ! minimum pt for the third lepton in pt
> 0.0 = ptl4min ! minimum pt for the fourth lepton in pt
> -1.0 = ptl1max ! maximum pt for the leading lepton in pt
> -1.0 = ptl2max ! maximum pt for the second lepton in pt
> -1.0 = ptl3max ! maximum pt for the third lepton in pt
> -1.0 = ptl4max ! maximum pt for the fourth lepton in pt
> #*********************************************************************
> # Control the Ht(k)=Sum of k leading jets *
> #*********************************************************************
> 0.0 = htjmin ! minimum jet HT=Sum(jet pt)
> -1.0 = htjmax ! maximum jet HT=Sum(jet pt)
> 0.0 = ihtmin !inclusive Ht for all partons (including b)
> -1.0 = ihtmax !inclusive Ht for all partons (including b)
> 0.0 = ht2min ! minimum Ht for the two leading jets
> 0.0 = ht3min ! minimum Ht for the three leading jets
> 0.0 = ht4min ! minimum Ht for the four leading jets
> -1.0 = ht2max ! maximum Ht for the two leading jets
> -1.0 = ht3max ! maximum Ht for the three leading jets
> -1.0 = ht4max ! maximum Ht for the four leading jets
> #***********************************************************************
> # Photon-isolation cuts, according to hep-ph/9801442 *
> # When ptgmin=0, all the other parameters are ignored *
> # When ptgmin>0, pta and draj are not going to be used *
> #***********************************************************************
> 20.0 = ptgmin ! Min photon transverse momentum
> 0.7 = R0gamma ! Radius of isolation code
> 1.0 = xn ! n parameter of eq.(3.4) in hep-ph/9801442
> 1.0 = epsgamma ! epsilon_gamma parameter of eq.(3.4) in hep-ph/9801442
> True = isoEM ! isolate photons from EM energy (photons and leptons)
> #*********************************************************************
> # WBF cuts *
> #*********************************************************************
> 0.0 = xetamin ! minimum rapidity for two jets in the WBF case
> 0.0 = deltaeta ! minimum rapidity for two jets in the WBF case
> #***********************************************************************
> # Turn on either the ktdurham or ptlund cut to activate *
> # CKKW(L) merging with Pythia8 [arXiv:1410.3012, arXiv:1109.4829] *
> #***********************************************************************
> -1.0 = ktdurham
> 0.5 = dparameter
> -1.0 = ptlund
> 1, 2, 3, 4, 5, 6, 21 = pdgs_for_merging_cut ! PDGs for two cuts above
> #*********************************************************************
> # maximal pdg code for quark to be considered as a light jet *
> # (otherwise b cuts are applied) *
> #*********************************************************************
> 4 = maxjetflavor ! Maximum jet pdg code
> #*********************************************************************
> #
> #*********************************************************************
> # Store info for systematics studies *
> # WARNING: Do not use for interference type of computation *
> #*********************************************************************
> False = use_syst ! Enable systematics studies
> #
> #**************************************
> # Parameter of the systematics study
> # will be used by SysCalc (if installed)
> #**************************************
> #
> 0.5 1 2 = sys_scalefact # factorization/renormalization scale factor
> None = sys_alpsfact # \alpha_s emission scale factors
> auto = sys_matchscale # variation of merging scale
> # PDF sets and number of members (0 or none for all members).
> NNPDF23_lo_as_0130_qed = sys_pdf # list of pdf sets
> # MSTW2008nlo68cl.LHgrid 1 = sys_pdf
> #
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Ernesto Arganda (earganda) said : #2

Thank you very much for the clarification, we have fixed the problem.