Mismatch between recalculated LO cross section and result from literature (arXiv: 1804.10017)

Asked by Pia Bredt on 2021-06-04

Dear MadGraph Team,

In order to do some comparisons I recalculated the LO cross section of process pp-> e+ nu_e mu- nu_mu with MG5 version 3.1.0 trying to reproduce the result of that process which was given in table 2 of arXiv: 1804.10017.

With all the input parameters and cuts (stated below) I got a LO value of 0.50925(8) pb which is about 21 sigma off the literature value of 0.51144(7) pb.

Since I could reproduce for example the result for the process pp->WWW with an agreement within 1 sigma while changing only the masses of the heavy vector bosons to the BW-masses of eq.(6.4) and (6.5) and setting their decay width to zero, I asked myself if I might have misinterpreted the notes to the off-shell parameters and cuts in arXiv: 1804.10017.

So my questions to make certain are

1. Is it correct, to take only the masses and widths with a "bar" (which is eq. (6.6-8) in the paper) into param_card.dat? And to which digit one has to round the numerical masses/width resulting eq. (6.6)?
2. Are the cuts set correctly as stated below in the run_card.dat? I. e. there should be no cut on the invariant masses, neither of the electron-muon nor the lepton-neutrino systems. Is that correct?
3. The parameters "muR_ref_fixed" and "muF_ref_fixed" in the run_card actually do not matter if the dynamical scale is chosen, right?
4. Is there any further cut or parameter I missed or is set incorrect concerning for example off-shell W bosons?
5. What does the "bwcutoff" parameter in the run_card mean? Is that maybe relevant for this problem?

I attached the content of the proc_card, param_card and run_card which I used for the process pp-> e+ nu_e mu- nu_mu.
I would be very happy if you could give any hint!

Best regards,
Pia

#************************************************************
#* MadGraph5_aMC@NLO *
#* *
#* * * *
#* * * * * *
#* * * * * 5 * * * * *
#* * * * * *
#* * * *
#* *
#* *
#* VERSION 3.1.0 2021-03-30 *
#* *
#* The MadGraph5_aMC@NLO Development Team - Find us at *
#* https://server06.fynu.ucl.ac.be/projects/madgraph *
#* *
#************************************************************
#* *
#* Command File for MadGraph5_aMC@NLO *
#* *
#* run as ./bin/mg5_aMC filename *
#* *
#************************************************************
set group_subprocesses Auto
set ignore_six_quark_processes False
set low_mem_multicore_nlo_generation False
set complex_mass_scheme False
set include_lepton_initiated_processes False
set gauge unitary
set loop_optimized_output True
set loop_color_flows False
set max_npoint_for_channel 0
set default_unset_couplings 99
set max_t_for_channel 99
set zerowidth_tchannel True
set nlo_mixed_expansion True
import model sm
define p = g u c d s u~ c~ d~ s~
define j = g u c d s u~ c~ d~ s~
define l+ = e+ mu+
define l- = e- mu-
define vl = ve vm vt
define vl~ = ve~ vm~ vt~
set fastjet /data1/bredt/local/bin/fastjet-config
set lhapdf /data1/bredt/local/bin/lhapdf-config
set fortran_compiler gfortran-7
set complex_mass_scheme True
set auto_convert_model T
import model loop_qcd_qed_sm_Gmu
define p = 21 2 4 1 3 -2 -4 -1 -3 5 -5 22 # pass to 5 flavors
define j = p
define pr=u c d s b u~ c~ d~ s~ b~ a g
generate pr pr > e+ ve mu- vm~ QCD=0 QED=4 [QED]
output ppenumunu

######################################################################
## PARAM_CARD AUTOMATICALY GENERATED BY MG5 FOLLOWING UFO MODEL ####
######################################################################
## ##
## Width set on Auto will be computed following the information ##
## present in the decay.py files of the model. ##
## See arXiv:1402.1178 for more details. ##
## ##
######################################################################

###################################
## INFORMATION FOR LOOP
###################################
Block loop
  666 9.115347e+01 # MU_R

###################################
## INFORMATION FOR MASS
###################################
Block mass
    6 1.733400e+02 # MT
   23 9.115347e+01 # MZ
   24 8.035785e+01 # MW
   25 1.250000e+02 # MH
## Dependent parameters, given by model restrictions.
## Those values should be edited following the
## analytical expression. MG5 ignores those values
## but they are important for interfacing the output of MG5
## to external program such as Pythia.
  1 0.000000 # d : 0.0
  2 0.000000 # u : 0.0
  3 0.000000 # s : 0.0
  4 0.000000 # c : 0.0
  5 0.000000 # b : 0.0
  11 0.000000 # e- : 0.0
  12 0.000000 # ve : 0.0
  13 0.000000 # mu- : 0.0
  14 0.000000 # vm : 0.0
  15 0.000000 # ta- : 0.0
  16 0.000000 # vt : 0.0
  21 0.000000 # g : 0.0
  22 0.000000 # a : 0.0
  9000002 91.15347 # ghz : MZ
  9000003 80.35785 # ghwp : MW
  9000004 80.35785 # ghwm : MW
  250 91.15347 # g0 : MZ
  251 80.35785 # g+ : MW
###################################
## INFORMATION FOR SMINPUTS
###################################
Block sminputs
    2 1.166390e-05 # Gf
    3 1.180000e-01 # aS

###################################
## INFORMATION FOR DECAY
###################################
DECAY 6 1.369180e+00 # WT
DECAY 23 2.494566e+00 # WZ
DECAY 24 2.088994e+00 # WW
DECAY 25 0.0 #4.074680e-03 # WH
## Dependent parameters, given by model restrictions.
## Those values should be edited following the
## analytical expression. MG5 ignores those values
## but they are important for interfacing the output of MG5
## to external program such as Pythia.
DECAY 1 0.000000 # d : 0.0
DECAY 2 0.000000 # u : 0.0
DECAY 3 0.000000 # s : 0.0
DECAY 4 0.000000 # c : 0.0
DECAY 5 0.000000 # b : 0.0
DECAY 11 0.000000 # e- : 0.0
DECAY 12 0.000000 # ve : 0.0
DECAY 13 0.000000 # mu- : 0.0
DECAY 14 0.000000 # vm : 0.0
DECAY 15 0.000000 # ta- : 0.0
DECAY 16 0.000000 # vt : 0.0
DECAY 21 0.000000 # g : 0.0
DECAY 22 0.000000 # a : 0.0
DECAY 250 2.495500 # g0 : WZ
DECAY 251 2.089700 # g+ : WW
#===========================================================
# QUANTUM NUMBERS OF NEW STATE(S) (NON SM PDG CODE)
#===========================================================

Block QNUMBERS 250 # g0
        1 0 # 3 times electric charge
        2 1 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 0 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 251 # g+
        1 3 # 3 times electric charge
        2 1 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)

#***********************************************************************
# 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. *
# *
# To display additional parameter, you can use the command: *
# update to_full *
#***********************************************************************
#
#*******************
# 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 *
#***********************************************************************
 10000 = 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) *
#***********************************************************************
 0.0002 = 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
 82000 = 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) *
#***********************************************************************
 F = fixed_ren_scale ! if .true. use fixed ren scale
 F = fixed_fac_scale ! if .true. use fixed fac scale
 91.15347 = muR_ref_fixed ! fixed ren reference scale
 91.15347 = 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
 False = 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.
 False = 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. *
# - If gamma_is_j, photons are also clustered *
# - 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 *
#***********************************************************************
  1.0 = jetalgo ! FastJet jet algorithm (1=kT, 0=C/A, -1=anti-kT)
  0.4 = jetradius ! The radius parameter for the jet algorithm
 0.0 = ptj ! Min jet transverse momentum
 4.5 = etaj ! Max jet abs(pseudo-rap) (a value .lt.0 means no cut)
 T = gamma_is_j! Wether to cluster photons as jets or not
#***********************************************************************
# Cuts on the charged leptons (e+, e-, mu+, mu-, tau+ and tau-) *
# More specific cuts can be specified in SubProcesses/cuts.f *
#***********************************************************************
  10.0 = ptl ! Min lepton transverse momentum
  2.5 = 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
  0.0 = mll_sf ! Min inv. mass of all opp. sign same-flavor lepton pairs
#***********************************************************************
# Fermion-photon recombination parameters *
# If Rphreco=0, no recombination is performed *
#***********************************************************************
 0.1 = Rphreco ! Minimum fermion-photon distance for recombination
 -1 = etaphreco ! Maximum abs(pseudo-rap) for photons to be recombined (a value .lt.0 means no cut)
 T = lepphreco ! Recombine photons and leptons together
 F = quarkphreco ! Recombine photons and quarks together
#***********************************************************************
# Photon-isolation cuts, according to hep-ph/9801442 *
# Not applied if gamma_is_j *
# When ptgmin=0, all the other parameters are ignored *
# More specific cuts can be specified in SubProcesses/cuts.f *
#***********************************************************************
  0.0 = ptgmin ! Min photon transverse momentum
  -1.0 = etagamma ! Max photon abs(pseudo-rap)
  0.4 = 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
 F = isoEM ! isolate photons from EM energy (photons and leptons)
#***********************************************************************
# Cuts associated to MASSIVE particles identified by their PDG codes. *
# All cuts are applied to both particles and anti-particles, so use *
# POSITIVE PDG CODES only. Example of the syntax is {6 : 100} or *
# {6:100, 25:200} for multiple particles *
#***********************************************************************
  {} = pt_min_pdg ! Min pT for a massive particle
  {} = pt_max_pdg ! Max pT for a massive particle
  {} = mxx_min_pdg ! inv. mass for any pair of (anti)particles
#***********************************************************************
# For aMCfast+APPLGRID use in PDF fitting (http://amcfast.hepforge.org)*
#***********************************************************************
 False = pineappl ! PineAPPL switch
# 0 = iappl ! aMCfast switch (0=OFF, 1=prepare grids, 2=fill grids)
#***********************************************************************
 5 = maxjetflavor

Question information

Language:
English Edit question
Status:
Open
For:
MadGraph5_aMC@NLO Edit question
Assignee:
davide.pagani.85 Edit question
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