Survey return zero cross section.

Asked by Mustafa Ashry on 2019-11-14

Hello,

I am working on a model which contains an heavy extra neutral Higgs boson h2 than the SM one.
I implemented the gluon-gluon-h2 and gamma-gamma-h2 effective vertices h2gg and h2aa in the same way hgg and haa were done for the SM Higgs. However, h2gg and h2aa are less than their corresponding SM ones due to the large h2 mass and the smallness of its couplings with the SM particles. Definitely, h2gg~O(10^-6), h2aa~O(10^-7) while hgg~O(10^-5), h2aa~O(10^-6).

When I generate either g g > h2 or h2 > a a, I obtain the following error

Survey return zero cross section.
   Typical reasons are the following:
   1) A massive s-channel particle has a width set to zero.
   2) The pdf are zero for at least one of the initial state particles
      or you are using maxjetflavor=4 for initial state b:s.
   3) The cuts are too strong.
   Please check/correct your param_card and/or your run_card.

To figure out where the problem comes from, I changed the h2gg and h2aa couplings with my hand and generated again and it worked well, but I wonder if there is some option to be set such that it considers the actual values of h2gg and h2aa as they dictated by the model benchmark point.
I tried set small_width_treatment 1E-14 in the run_card but it throws the same error message above.

Thanks in advance

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Mustafa Ashry
Solved:
2019-11-15
Last query:
2019-11-15
Last reply:
2019-11-15
Mustafa Ashry (mashry) said : #1

#*********************************************************************
# 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 *
# *
# To display more options, you can type the command: *
# update full_run_card *
#*********************************************************************
#
#*******************
# 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. *
#*********************************************************************
  10 = 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
# To see polarised beam options: type "update beam_pol"
#*********************************************************************
# PDF CHOICE: this automatically fixes also alpha_s and its evol. *
#*********************************************************************
  nn23lo1 = pdlabel ! PDF set
  230000 = lhaid ! if pdlabel=lhapdf, this is the lhapdf number
# To see heavy ion options: type "update ion_pdf"
#*********************************************************************
# 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
  -1 = 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
  5 = 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) *
#*********************************************************************
  0.0 = ptj ! minimum pt for the jets
  0.0 = 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)
  {} = pt_min_pdg ! pt cut for other particles (use pdg code). Applied on particle and anti-particle
  {} = pt_max_pdg ! pt cut for other particles (syntax e.g. {6: 100, 25: 50})
#*********************************************************************
# 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
  {} = e_min_pdg ! E cut for other particles (use pdg code). Applied on particle and anti-particle
  {} = e_max_pdg ! E cut for other particles (syntax e.g. {6: 100, 25: 50})
#*********************************************************************
# Maximum and minimum absolute rapidity (for max, -1 means no cut) *
#*********************************************************************
  -1.0 = etaj ! max rap for the jets
  -1.0 = etab ! max rap for the b
  -1.0 = 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
  {} = eta_min_pdg ! rap cut for other particles (use pdg code). Applied on particle and anti-particle
  {} = eta_max_pdg ! rap cut for other particles (syntax e.g. {6: 2.5, 23: 5})
#*********************************************************************
# 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
  {} = mxx_min_pdg ! min invariant mass of a pair of particles X/X~ (e.g. {6:250})
  {'default': False} = mxx_only_part_antipart ! if True the invariant mass is applied only
                       ! to pairs of particle/antiparticle and not to pairs of the same pdg codes.
#*********************************************************************
# 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 *
#***********************************************************************
  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
  -1.0 = 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] *
#***********************************************************************
  0.0 = ktdurham
  0.0 = dparameter
  0.0 = ptlund
  1, 2, 3, 4, 5, 6, 21, 106, 107, 108 = 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
#
  systematics = systematics_program ! none, systematics [python], SysCalc [depreceted, C++]
['--mur=0.5,1,2', '--muf=0.5,1,2', '--pdf=errorset'] = systematics_arguments ! see: https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/Systematics#Systematicspythonmodule
# Syscalc is deprecated but to see the associate options type'update syscalc'#*********************************************************************
# Additional hidden parameters
#*********************************************************************
  ['--mur=0.5,1,2', '--muf=0.5,1,2', '--pdf=errorset'] = systematics_arguments # Choose the argment to pass to the systematics command. like --mur=0.25,1,4. Look at the help of the systematics function for more details.
  1e-30 = small_width_treatment # generation where the width is below VALUE times mass will be replace by VALUE times mass for the computation. The cross-section will be corrected assuming NWA. Not used for loop-induced process

Mustafa Ashry (mashry) said : #2

######################################################################
## 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 ALRMINPUTS
###################################
Block alrminputs
    1 5.000000e-01 # lm2
    2 6.000000e-01 # lm3
    3 3.000000e-01 # al1
    4 1.000000e-01 # al2
    5 5.000000e-01 # al3
    6 1.000000e+01 # tb
    7 -1.000000e+01 # mu3

###################################
## INFORMATION FOR CKMBLOCK
###################################
Block ckmblock
    1 2.210000e-01 # s12
    2 4.000000e-02 # s23
    3 3.500000e-03 # s13

###################################
## INFORMATION FOR MASS
###################################
Block mass
    1 5.040000e-03 # MD
    2 2.550000e-03 # MU
    3 1.010000e-01 # MS
    4 1.270000e+00 # MC
    5 4.700000e+00 # MB
    6 1.720000e+02 # MT
   11 5.110000e-04 # Me
   12 1.000000e-12 # Mve
   13 1.056600e-01 # MMU
   14 8.900000e-12 # Mvm
   15 1.777000e+00 # MTA
   16 5.040000e-11 # Mvt
   23 9.118760e+01 # MZ
   24 8.037900e+01 # MW
   25 1.250000e+02 # mh0
  103 3.000000e+02 # Mne
  104 5.000000e+02 # Mnm
  105 7.000000e+02 # Mnt
  106 3.000000e+02 # MDD
  107 6.000000e+02 # MDS
  108 1.000000e+03 # MDB
## 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.
  21 0.000000 # g : 0.0
  22 0.000000 # a : 0.0
  26 4657.688821 # h1 : ma1
  27 724.802170 # h2 : cmath.sqrt(-mh0__exp__2 + trmh - cmath.sqrt((-4*detmh)/mh0__exp__2 + (-mh0__exp__2 + trmh)**2))/sqrt__2
  28 8057.486311 # h3 : cmath.sqrt(-mh0__exp__2 - mh2__exp__2 + trmh)
  29 4657.688821 # a1 : cmath.sqrt(2*k__exp__2*lm2 + (-al2 + al3)*(vL__exp__2 + vR__exp__2) - (mu3*vL*vR)/(k*sqrt__2))
  30 724.697678 # a2 : cmath.sqrt(-((mu3*(vL__exp__2*vR__exp__2 + k__exp__2*(vL__exp__2 + vR__exp__2)))/(k*vL*vR)))/nb__2__exp__0_25
  31 740.735229 # h1+ : cmath.sqrt((vev__exp__2*((-al2 + al3)*k*vL - (mu3*vR)/sqrt__2))/(k*vL))
  32 4653.915105 # h2- : cmath.sqrt((vp__exp__2*((-al2 + al3)*k*vR - (mu3*vL)/sqrt__2))/(k*vR))
  100 2889.769831 # zp : cmath.sqrt(MLL + MRR - MZ__exp__2)
  101 2439.524522 # wp+ : (ee*vp)/(2.*sw)

###################################
## INFORMATION FOR SMINPUTS
###################################
Block sminputs
    1 1.279000e+02 # aEWM1
    2 1.166370e-05 # Gf
    3 1.184000e-01 # aS
    4 2.234300e-01 # sw2

###################################
## INFORMATION FOR YUKAWA
###################################
Block yukawa
    1 5.040000e-03 # ymdo
    2 2.550000e-03 # ymup
    3 1.010000e-01 # yms
    4 1.270000e+00 # ymc
    5 4.700000e+00 # ymb
    6 1.720000e+02 # ymt
    7 3.000000e+02 # ymddo
    8 6.000000e+02 # ymds
    9 1.000000e+03 # ymdb
   11 5.110000e-04 # yme
   12 1.000000e-12 # ymnue
   13 1.056600e-01 # ymm
   14 8.900000e-12 # ymnum
   15 1.777000e+00 # ymtau
   16 5.040000e-11 # ymnutau
   17 3.000000e+02 # ymne
   18 5.000000e+02 # ymnm
   19 7.000000e+02 # ymntau

###################################
## INFORMATION FOR DECAY
###################################
DECAY 6 1.508336e+00 # WT
DECAY 23 2.520000e+00 # WZ
DECAY 24 2.110000e+00 # WW
DECAY 25 2.259167e-04 # WH0
DECAY 26 9.500000e-01 # WH1
DECAY 27 6.092500e-04 # WH2
DECAY 28 5.017665e-03 # WH3
DECAY 29 9.500000e-01 # WA1
DECAY 30 1.450000e+00 # WA2
DECAY 31 1.000000e+00 # WHP1
DECAY 32 3.250000e-01 # WHM2
DECAY 100 1.320000e+01 # WZp
DECAY 101 3.040000e+00 # WWp
DECAY 104 7.090000e-04 # Wnm
DECAY 105 1.130000e+00 # Wnt
DECAY 106 0.000000e+00 # Wdd
DECAY 107 2.620000e-01 # Wds
DECAY 108 9.850000e+00 # Wdb
## 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 103 0.000000 # ne : 0.0
#===========================================================
# QUANTUM NUMBERS OF NEW STATE(S) (NON SM PDG CODE)
#===========================================================

Block QNUMBERS 100 # zp
        1 0 # 3 times electric charge
        2 3 # 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 101 # wp+
        1 3 # 3 times electric charge
        2 3 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 103 # ne
        1 0 # 3 times electric charge
        2 2 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 104 # nm
        1 0 # 3 times electric charge
        2 2 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 105 # nt
        1 0 # 3 times electric charge
        2 2 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 106 # dd
        1 -1 # 3 times electric charge
        2 2 # number of spin states (2S+1)
        3 3 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 107 # ds
        1 -1 # 3 times electric charge
        2 2 # number of spin states (2S+1)
        3 3 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 108 # db
        1 -1 # 3 times electric charge
        2 2 # number of spin states (2S+1)
        3 3 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 26 # h1
        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 27 # h2
        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 28 # h3
        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 29 # a1
        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 30 # a2
        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 31 # h1+
        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)
Block QNUMBERS 32 # h2-
        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)

Hi,

> I tried set small_width_treatment 1E-14 in the run_card but it throws the same error message above.

I would not recomend to put that parameter smaller than 1e-12.
This is certainly the reason for your crash actually (i.e. numerical inacuracy)
But keeping the default to 1e-6 or 1e-8 (not sure) should be the best choice.

Cheers,

Olivier

> On 14 Nov 2019, at 19:16, Mustafa Ashry <email address hidden> wrote:
>
> New question #685877 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/685877
>
> Hello,
>
> I am working on a model which contains an heavy extra neutral Higgs boson h2 than the SM one.
> I implemented the gluon-gluon-h2 and gamma-gamma-h2 effective vertices h2gg and h2aa in the same way hgg and haa were done for the SM Higgs. However, h2gg and h2aa are less than their corresponding SM ones due to the large h2 mass and the smallness of its couplings with the SM particles. Definitely, h2gg~O(10^-6), h2aa~O(10^-7) while hgg~O(10^-5), h2aa~O(10^-6).
>
> When I generate either g g > h2 or h2 > a a, I obtain the following error
>
> Survey return zero cross section.
> Typical reasons are the following:
> 1) A massive s-channel particle has a width set to zero.
> 2) The pdf are zero for at least one of the initial state particles
> or you are using maxjetflavor=4 for initial state b:s.
> 3) The cuts are too strong.
> Please check/correct your param_card and/or your run_card.
>
> To figure out where the problem comes from, I changed the h2gg and h2aa couplings with my hand and generated again and it worked well, but I wonder if there is some option to be set such that it considers the actual values of h2gg and h2aa as they dictated by the model benchmark point.
> I tried set small_width_treatment 1E-14 in the run_card but it throws the same error message above.
>
> Thanks in advance
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Mustafa Ashry (mashry) said : #4

Hello Oliver,

Thank you for your reply. Actually, the problem is not with the limit of small_width_treatment 1E-14. Anyway, I set it to 1e^-6 and it didn't work too.
However, I figured out that the problem is with the h2gg and h2aa effective couplings as they contain the ArcSin(Sqrt(xp)), where the parameter xp for a particle p is xp=mh2^2/(4mp^2) and, for example in my case for mh2~400 Gev, and for the top quark in case of the h2gg coupling it is xt>1, and the function ArcSin(x) is not real when x>1. I don't know why python can't deal with it although its contribution into the coupling is defined to be real using the abs function and the cmath library as cmath.asin(cmath.sqrt(xp))**2, but when I changed its value so that xt<1, it works whatever the value of small_width_treatment, while conversely, it doesn't work when the numerical value of xt is greater than 1. I don't know why MG can't interpret asin(x) for x>1 in the complex domain through the cmath library, while it works normally in python away from MG, and that there are other parameters in the madel which uses cmath in their definition but MG can deal with, that is the problem is asin itself. Any hind is appreciated, and thanks again.

The reason is that we are not using python for fortran for the computation. (python is too slow)
and it has indeed some limitation for the asin:
https://gcc.gnu.org/onlinedocs/gcc-5.2.0/gfortran/ASIN.html

Cheers,

Olivier

> On 15 Nov 2019, at 00:37, Mustafa Ashry <email address hidden> wrote:
>
> Question #685877 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/685877
>
> Status: Answered => Open
>
> Mustafa Ashry is still having a problem:
> Hello Oliver,
>
> Thank you for your reply. Actually, the problem is not with the limit of small_width_treatment 1E-14. Anyway, I set it to 1e^-6 and it didn't work too.
> However, I figured out that the problem is with the h2gg and h2aa effective couplings as they contain the ArcSin(Sqrt(xp)), where the parameter xp for a particle p is xp=mh2^2/(4mp^2) and, for example in my case for mh2~400 Gev, and for the top quark in case of the h2gg coupling it is xt>1, and the function ArcSin(x) is not real when x>1. I don't know why python can't deal with it although its contribution into the coupling is defined to be real using the abs function and the cmath library as cmath.asin(cmath.sqrt(xp))**2, but when I changed its value so that xt<1, it works whatever the value of small_width_treatment, while conversely, it doesn't work when the numerical value of xt is greater than 1. I don't know why MG can't interpret asin(x) for x>1 in the complex domain through the cmath library, while it works normally in python away from MG, and that there are other parameters in the madel which uses cmath in their definition but MG can deal with, that is the problem is asin itself. Any hind is appreciated, and thanks again.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Mustafa Ashry (mashry) said : #6

Hi Olivier,
Thanks again. But the UFO model files were passed into MG from FR and they are produced as .py files, what shall I do then to let MG understand this issue, can I write it using fortran format inside the .py files?

Mustafa Ashry (mashry) said : #7

The problem was solved, thank you.

Great.

Can you comment on how you did it for the next person facing a similar issue?

Thanks,

Olivier

> On 15 Nov 2019, at 03:09, Mustafa Ashry <email address hidden> wrote:
>
> Question #685877 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/685877
>
> Status: Open => Solved
>
> Mustafa Ashry confirmed that the question is solved:
> The problem was solved, thank you.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Mustafa Ashry (mashry) said : #9

Hello Olivier,

Thanks, of course, it's a pleasure.

Tho original expression for the hgg and haa loop integrals contain the two-rules function f(xp) defined as follows
( ref: arXiv:1108.5872 [hep-ph] ):

[ArcSin(Sqrt(xp))]^2, for xp<=1, (1)
and
(-1/4) [Log[{1+Sqrt(1-(1/xp))}/{1-Sqrt(1-(1/xp))}]-I pi]^2, for xp>1, (2)
where for a loop-particle p,
xp=mh^2/(4mp^2). (3)

However, on the complex domain, I noticed that the two functions rules (1) and (2) are conjugate to each others whenever x>1, and thus I used to use only (1) for the both cases, but it seems that fortran, as you said, couldn't defince (1) for xp>1.
All waht I did then was to use (2), which was the original formula, for values xp>1, again, so it was my mistake from the beginning.

Thanks!

Mustafa

Mustafa Ashry (mashry) said : #10

The link for the implementation model file is here
https://feynrules.irmp.ucl.ac.be/attachment/wiki/ALRM/ALRM_LO_hgg_haa.fr

Cheers,

Mustafa

Thanks a lot for the information,

Olivier

Mustafa Ashry (mashry) said : #12

Thank you, it's my pleasure!

Mustafa