ttbb process at LO/NLO
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/
# *
# 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
# 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=
#******
# 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
#******
# 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/
# dynamical_
#******
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_
! 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_
! 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://
# 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*
# 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://
#******
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/
# *
# 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=
#******
# 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_
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
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.
#******
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*
#******
15.0 = bwcutoff ! (M+/-bwcutoff*
#******
# Apply pt/E/eta/
# (note that etmiss/
#******
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_
#******
# 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/
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_
# MSTW2008nlo68cl
#
Question information
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- Ernesto Arganda
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