draj=0.0 makes madgraph5 fail to reach target number of events

Asked by Lee, Dongsub on 2017-07-27

Dear MadGraph5 team,

Currently I'm trying to generate following process,
p p > a a
p p > a a j
with the model loop_sm(Actually I couldn't see model-dependence of the problem what I want to ask about).

However, when I set `draj' in the run_card.dat 0.0, madevent fails to reach target number of events after finishing refine.
Meanwhile, I want to make draj as small as possible as I can.
Is there any way to take draj=0.0 while madevent still works well?

Now I'm using the version 2.5.5 and I attach command file for running madevent, log file, and run_card.dat

==========================[ command file ]==========================
generate_events
shower=PYTHIA8
analysis=off
delphes=on
done
set run_tag pp2aa_1j_sm
set iseed 1
set nevents 20000
set ebeam1 7000
set ebeam2 7000
set MT 173
set ymt 173
set WT 1.4915
set MH 125
set pdlabel lhapdf
set lhaid 11000
set dynamical_scale_choice 4
set cut_decays False
set ptj 20.0
set ptb 0.0
set ptl 10.0
set pta 10.0
set etaj 5.0
set etab -1.0
set etal 2.5
set etaa 2.5
set drjj 0.0
set drbb 0.0
set drll 0.0
set draa 0.0
set drbj 0.0
set draj 0.0
set drjl 0.0
set drab 0.0
set drbl 0.0
set dral 0.0
set mmjj 0.0
set mmbb 0.0
set mmaa 0.0
set mmll 0.0
set ickkw 1
set xqcut 20.0
set auto_ptj_mjj True
set use_syst False
0
exit
=================================================================

==========================[ run_card.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) *
#*********************************************************************
  pp2aa_1j_sm = 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. *
#*********************************************************************
  20000 = nevents ! Number of unweighted events requested
  1 = 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
  7000.0 = ebeam1 ! beam 1 total energy in GeV
  7000.0 = 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
  11000 = 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
  91.188 = scale ! fixed ren scale
  91.188 = dsqrt_q2fact1 ! fixed fact scale for pdf1
  91.188 = dsqrt_q2fact2 ! fixed fact scale for pdf2
  4 = 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)
#*********************************************************************
  1 = 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
  True = auto_ptj_mjj ! Automatic setting of ptj and mjj if xqcut >0
                                   ! (turn off for VBF and single top processes)
  20.0 = 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) *
#*********************************************************************
  20.0 = ptj ! minimum pt for the jets
  0.0 = ptb ! minimum pt for the b
  10.0 = pta ! minimum pt for the photons
  10.0 = ptl ! minimum pt for the charged leptons
  0.0 = misset ! minimum missing Et (sum of neutrino's momenta)
  0.0 = ptheavy ! minimum pt for one heavy final state
  -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) *
#*********************************************************************
  5.0 = etaj ! max rap for the jets
  -1.0 = etab ! max rap for the b
  2.5 = etaa ! max rap for the photons
  2.5 = 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 = 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 *
#***********************************************************************
  0.0 = ptgmin ! Min photon transverse momentum
  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
  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
  0.4 = 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
  0.5 1 2 = 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
#
=================================================================

==========================[ log file ]==========================
[?1034h************************************************************
* *
* W E L C O M E to *
* M A D G R A P H 5 _ a M C @ N L O *
* M A D E V E N T *
* *
* * * *
* * * * * *
* * * * * 5 * * * * *
* * * * * *
* * * *
* *
* VERSION 2.5.5 20xx-xx-xx *
* *
* The MadGraph5_aMC@NLO Development Team - Find us at *
* https://server06.fynu.ucl.ac.be/projects/madgraph *
* *
* Type 'help' for in-line help. *
* *
************************************************************
INFO: load configuration from /data8/dslee/madgraph255/pp2aa_1j_sm/Cards/me5_configuration.txt
INFO: load configuration from /data8/dslee/madgraph255/input/mg5_configuration.txt
INFO: load configuration from /data8/dslee/madgraph255/pp2aa_1j_sm/Cards/me5_configuration.txt
Using default eps viewer "evince". Set another one in ./input/mg5_configuration.txt
Using default web browser "firefox". Set another one in ./input/mg5_configuration.txt
import command ./Run_MG5_User/run_pp2aa_1j_sm_1.cmd
generate_events
Using old syntax. Please check that we run what you expect.
set run_tag pp2aa_1j_sm
INFO: modify parameter run_tag of the run_card.dat to pp2aa_1j_sm 
set iseed 1
INFO: modify parameter iseed of the run_card.dat to 1 
set nevents 20000
INFO: modify parameter nevents of the run_card.dat to 20000 
set ebeam1 7000
INFO: modify parameter ebeam1 of the run_card.dat to 7000 
set ebeam2 7000
INFO: modify parameter ebeam2 of the run_card.dat to 7000 
set MT 173
INFO: modify param_card information BLOCK mass with id (6,) set to 173.0 
set ymt 173
INFO: modify param_card information BLOCK yukawa with id (6,) set to 173.0 
set WT 1.4915
INFO: modify param_card information BLOCK decay with id (6,) set to 1.4915 
set MH 125
INFO: modify param_card information BLOCK mass with id (25,) set to 125.0 
set pdlabel lhapdf
INFO: modify parameter pdlabel of the run_card.dat to lhapdf 
set lhaid 11000
INFO: modify parameter lhaid of the run_card.dat to 11000 
set dynamical_scale_choice 4
INFO: modify parameter dynamical_scale_choice of the run_card.dat to 4 
set cut_decays False
INFO: modify parameter cut_decays of the run_card.dat to False 
set ptj 20.0
INFO: modify parameter ptj of the run_card.dat to 20.0 
set ptb 0.0
INFO: modify parameter ptb of the run_card.dat to 0.0 
set ptl 10.0
INFO: modify parameter ptl of the run_card.dat to 10.0 
set pta 10.0
INFO: modify parameter pta of the run_card.dat to 10.0 
set etaj 5.0
INFO: modify parameter etaj of the run_card.dat to 5.0 
set etab -1.0
INFO: modify parameter etab of the run_card.dat to -1.0 
set etal 2.5
INFO: modify parameter etal of the run_card.dat to 2.5 
set etaa 2.5
INFO: modify parameter etaa of the run_card.dat to 2.5 
set drjj 0.0
INFO: modify parameter drjj of the run_card.dat to 0.0 
set drbb 0.0
INFO: modify parameter drbb of the run_card.dat to 0.0 
set drll 0.0
INFO: modify parameter drll of the run_card.dat to 0.0 
set draa 0.0
INFO: modify parameter draa of the run_card.dat to 0.0 
set drbj 0.0
INFO: modify parameter drbj of the run_card.dat to 0.0 
set draj 0.0
INFO: modify parameter draj of the run_card.dat to 0.0 
set drjl 0.0
INFO: modify parameter drjl of the run_card.dat to 0.0 
set drab 0.0
INFO: modify parameter drab of the run_card.dat to 0.0 
set drbl 0.0
INFO: modify parameter drbl of the run_card.dat to 0.0 
set dral 0.0
INFO: modify parameter dral of the run_card.dat to 0.0 
set mmjj 0.0
INFO: modify parameter mmjj of the run_card.dat to 0.0 
set mmbb 0.0
INFO: modify parameter mmbb of the run_card.dat to 0.0 
set mmaa 0.0
INFO: modify parameter mmaa of the run_card.dat to 0.0 
set mmll 0.0
INFO: modify parameter mmll of the run_card.dat to 0.0 
set ickkw 1
INFO: modify parameter ickkw of the run_card.dat to 1 
set xqcut 20.0
INFO: modify parameter xqcut of the run_card.dat to 20.0 
set auto_ptj_mjj True
INFO: modify parameter auto_ptj_mjj of the run_card.dat to True 
set use_syst False
INFO: modify parameter use_syst of the run_card.dat to False 
INFO: Update the dependent parameter of the param_card.dat
Generating 20000 events with run name run_02
survey run_02
INFO: compile directory
INFO: Using LHAPDF v6.1.6 interface for PDFs
compile Source Directory
Using random number seed offset = 1
INFO: Running Survey
Creating Jobs
Working on SubProcesses
INFO: P2_gq_aaq
INFO: P2_qq_aag
INFO: P1_qq_aa
INFO: Idle: 1, Running: 3, Completed: 1 [ current time: 15h28 ]
INFO: Idle: 0, Running: 4, Completed: 1 [ current time: 15h28 ]
INFO: Idle: 0, Running: 0, Completed: 5 [ 3.2s ]
INFO: Idle: 0, Running: 0, Completed: 5 [ 3.2s ]
INFO: End survey
refine 20000
Creating Jobs
INFO: Refine results to 20000
INFO: Generating 20000.0 unweigthed events.
INFO: Effective Luminosity 58.195644056 pb^-1
INFO: need to improve 4 channels
Current estimate of cross-section: 412.402 +- 7.71347790859
    P2_gq_aaq
    P2_qq_aag
    P1_qq_aa
INFO: Idle: 0, Running: 25, Completed: 0 [ current time: 15h29 ]
INFO: Idle: 0, Running: 11, Completed: 14 [ 7.7s ]
INFO: Idle: 0, Running: 8, Completed: 17 [ 16m 24s ]
INFO: Idle: 0, Running: 7, Completed: 18 [ 17m 17s ]
INFO: Idle: 0, Running: 3, Completed: 22 [ 21m 9s ]
INFO: Idle: 0, Running: 0, Completed: 25 [ 22m 12s ]
INFO: Idle: 0, Running: 0, Completed: 25 [ 22m 12s ]
INFO: Combining runs
INFO: finish refine
refine 20000
Creating Jobs
INFO: Refine results to 20000
INFO: Generating 20000.0 unweigthed events.
INFO: Effective Luminosity 45.4698743137 pb^-1
INFO: need to improve 2 channels
Current estimate of cross-section: 527.822 +- 4.87649843199
    P2_gq_aaq
    P2_qq_aag
    P1_qq_aa
INFO: Idle: 0, Running: 14, Completed: 0 [ current time: 15h51 ]
INFO: Idle: 0, Running: 13, Completed: 1 [ 18m 4s ]
INFO: Idle: 0, Running: 10, Completed: 4 [ 19m 1s ]
INFO: Idle: 0, Running: 8, Completed: 6 [ 22m 5s ]
INFO: Idle: 0, Running: 4, Completed: 10 [ 23m 10s ]
INFO: Idle: 0, Running: 0, Completed: 14 [ 24m 17s ]
INFO: Idle: 0, Running: 0, Completed: 14 [ 24m 17s ]
INFO: Combining runs
INFO: finish refine
INFO: Combining Events
INFO: fail to reach target 20000
  === Results Summary for run: run_02 tag: pp2aa_1j_sm ===

     Cross-section : 519.1 +- 1.197 pb
     Nb of events : 650

store_events
INFO: Storing parton level results
INFO: End Parton
reweight -from_cards
decay_events -from_cards
INFO: Running Pythia8 [arXiv:1410.3012]
No user-defined value for Pythia8 parameter 'JetMatching:nJetMax'. Setting it automatically to 1.
Splitting .lhe event file for PY8 parallelization...
Submitting Pythia8 jobs...
Pythia8 shower jobs: 1 Idle, 5 Running, 0 Done [0 second]
Pythia8 shower jobs: 0 Idle, 5 Running, 1 Done [14 seconds]
Pythia8 shower jobs: 0 Idle, 4 Running, 2 Done [14 seconds]
Pythia8 shower jobs: 0 Idle, 3 Running, 3 Done [14 seconds]
Pythia8 shower jobs: 0 Idle, 2 Running, 4 Done [15 seconds]
Pythia8 shower jobs: 0 Idle, 1 Running, 5 Done [15 seconds]
Pythia8 shower jobs: 0 Idle, 0 Running, 6 Done [16 seconds]
Merging results from the split PY8 runs...
INFO: Create matching plots for Pythia8
INFO: Pythia8 shower finished after 19 seconds.
INFO: prepare delphes run
INFO: Running Delphes
INFO: If you are interested in lhco output. please run root2lhco converter.
INFO: or edit bin/internal/run_delphes3 to run the converter automatically.
INFO: delphes done
  === Results Summary for run: run_02 tag: pp2aa_1j_sm ===

     Cross-section : 519.1 +- 1.197 pb
     Nb of events : 650
     Matched cross-section : 500.7 +- 3.935 pb
     Nb of events after matching/merging : 627
     Nb of events after merging : 627

INFO: storing files of previous run
INFO: Storing Pythia8 files of previous run
INFO: Done
exit
INFO:

quit
INFO:

INFO:

launch in debug mode
=================================================================

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
2017-07-28
Last query:
2017-07-28
Last reply:
2017-07-27
Lee, Dongsub (dongsub.lee) said : #1

I tested draj by varying this from 0.0 to 0.4 and it makes dramatic change on running time and, furthermore, the main source making this failure was draj=0.0, for me to see.

Always thanks for great work of the team.
Best regards,
Lee

Hi,

if you do not put any cut, you have a singularity related that you can have a colinear photon emitted in the direction of one jet.
The mass of such propagator is then exactly zero and the propagator is then one divided by zero.
This is a colinear singulartity which requires NLO EW (or EW shower) in order to be handle correctly.

Cheers,

Olivier

Lee, Dongsub (dongsub.lee) said : #3

Thanks Olivier Mattelaer, that solved my question.