Crash Madgraph with ALP model

Asked by FEDERICA giacchino on 2019-08-27

Hi,

I am working with an ALP model where the alp particle is coupled with electrons (here you can find the model
https://www.dropbox.com/sh/w32gh1qfl1ttd4n/AADl9TZb5ZJTMsjk63-vT8sra?dl=0). When the mass of alp is near 16.7 MeV the cross-section has instabilities (the error is larger than cross-section) and the number of events is zero. I have checked everything also analytically. The value of energy beam is 550MeV so the resonance is far from 16.7 MeV.

Do you know why I observe this instability?

Thanks
Federica

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Last query:
2019-08-29
Last reply:
2019-09-05

Can you put the banner? such that I can see which process you are looking for and that I know all relevant parameter (mass of which particles, scale choice used, width,...)

With that few information I can write a book on all the mistake that can happens.

Cheers,

Olivier

> On 27 Aug 2019, at 12:23, FEDERICA giacchino <email address hidden> wrote:
>
> New question #683402 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/683402
>
> Hi,
>
> I am working with an ALP model where the alp particle is coupled with electrons (here you can find the model
> https://www.dropbox.com/sh/w32gh1qfl1ttd4n/AADl9TZb5ZJTMsjk63-vT8sra?dl=0). When the mass of alp is near 16.7 MeV the cross-section has instabilities (the error is larger than cross-section) and the number of events is zero. I have checked everything also analytically. The value of energy beam is 550MeV so the resonance is far from 16.7 MeV.
>
> Do you know why I observe this instability?
>
> Thanks
> Federica
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Yes sorry I forgot it.

Here you have the banner:

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<header>
<!--
#*********************************************************************
# *
# MadGraph5_aMC@NLO *
# *
# Going Beyond *
# *
# http://madgraph.hep.uiuc.edu *
# http://madgraph.phys.ucl.ac.be *
# http://amcatnlo.cern.ch *
# *
# The MadGraph5_aMC@NLO team *
# *
#....................................................................*
# *
# This file contains all the information necessary to reproduce *
# the events generated: *
# *
# 1. software version *
# 2. proc_card : code generation info including model *
# 3. param_card : model primary parameters in the LH format *
# 4. run_card : running parameters (collider and cuts) *
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#* VERSION 3.0.0 2018-05-01 *
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#* 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 default_unset_couplings 99
set group_subprocesses Auto
set ignore_six_quark_processes False
set loop_optimized_output True
set include_lepton_initiated_processes False
set loop_color_flows False
set gauge unitary
set complex_mass_scheme False
set max_npoint_for_channel 0
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~
import model alp
generate e- e+ > a alp
output epaalp
]]>
</MG5ProcCard>
<MGProcCard>
#*********************************************************************
# MadGraph/MadEvent *
# http://madgraph.hep.uiuc.edu *
# *
# proc_card.dat *
#*********************************************************************
# *
# This Files is generated by MADGRAPH 5 *
# *
# WARNING: This Files is generated for MADEVENT (compatibility issue)*
# This files is NOT a valid MG4 proc_card.dat *
# Running this in MG4 will NEVER reproduce the result of MG5*
# *
#*********************************************************************
#*********************************************************************
# Process(es) requested : mg2 input *
#*********************************************************************
# Begin PROCESS # This is TAG. Do not modify this line
e- e+ > a alp #Process
# Be carefull the coupling are here in MG5 convention

end_coup # End the couplings input

done # this tells MG there are no more procs
# End PROCESS # This is TAG. Do not modify this line
#*********************************************************************
# Model information *
#*********************************************************************
# Begin MODEL # This is TAG. Do not modify this line
alp
# End MODEL # This is TAG. Do not modify this line
#*********************************************************************
# Start multiparticle definitions *
#*********************************************************************
# Begin MULTIPARTICLES # This is TAG. Do not modify this line

# End MULTIPARTICLES # This is TAG. Do not modify this line
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<![CDATA[
#*********************************************************************
# MadGraph5_aMC@NLO *
# *
# run_card.dat MadEvent *
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# 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 *
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# To display more options, you can type the command: *
* update full_run_card *
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#
#*******************
# Running parameters
#*******************
#
#*********************************************************************
# Tag name for the run (one word) *
#*********************************************************************
  tag_1 = run_tag ! name of the run
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# 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. *
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  10000 = nevents ! Number of unweighted events requested
 774 = 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 *
#*********************************************************************
     0 = lpp1 ! beam 1 type
     0 = lpp2 ! beam 2 type
    0.550 = ebeam1 ! beam 1 total energy in GeV
     0.0 = 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"
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# 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
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# Matching parameter (MLM only)
#*********************************************************************
 0 = ickkw ! 0 no matching, 1 MLM
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                                   ! (turn off for VBF and single top processes)
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 None = bias_module ! Bias type of bias, [None, ptj_bias, -custom_folder-]
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#*******************************
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#
#
#*********************************************************************
# BW cutoff (M+/-bwcutoff*Gamma) ! Define on/off-shell for "$" and decay
#*********************************************************************
  15.0 = bwcutoff ! (M+/-bwcutoff*Gamma)
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# Apply pt/E/eta/dr/mij/kt_durham cuts on decay products or not
# (note that etmiss/ptll/ptheavy/ht/sorted cuts always apply)
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   False = cut_decays ! Cut decay products
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# Standard Cuts *
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# Minimum and maximum pt's (for max, -1 means no cut) *
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 0.0 = ptj ! minimum pt for the jets
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 -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
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#*********************************************************************
# 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
 -1.0 = 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
   = 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'
]]>
</MGRunCard>
<slha>
######################################################################
## 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 MASS
###################################
Block mass
   11 5.110000e-04 # Me
   13 1.056600e-01 # MMU
   15 1.777000e+00 # MTA
  9000001 17.000e-03 # Malp (LA MASSA È DATA IN GeV)
## 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.
  22 0.000000 # a : 0.0

###################################
## INFORMATION FOR SMINPUTS
###################################
Block sminputs
    1 1.279000e+02 # aEWM1
    2 1.184000e-01 # aS
    3 0.0 # gAlp
    4 5.11e-4 # yal

###################################
## INFORMATION FOR DECAY
###################################

Block QNUMBERS 9000001 # alp
        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)
#
#*************************
# Decay widths *
#*************************
#
# PDG Width
DECAY 11 0.000000e+00
#
# PDG Width
DECAY 13 0.000000e+00
#
# PDG Width
DECAY 15 0.000000e+00
#
# PDG Width
DECAY 22 0.000000e+00
#
# PDG Width
DECAY 9000001 3.958089e-10
# BR NDA ID1 ID2 ...
   9.999874e-01 2 11 -11 # 3.95803968388e-10
   1.256564e-05 2 22 22 # 4.97359197162e-15
</slha>
<MGGenerationInfo>
# Number of Events : 10000
# Integrated weight (pb) : 6.28850000067e+13
</MGGenerationInfo>
</header>
</LesHouchesEvents>

this is from terminal

INFO: fail to reach target 10000
  === Results Summary for run: run_09 tag: tag_1 ===

     Cross-section : 6.289e+13 +- 3.144e+13 pb
     Nb of events : 3

store_events
INFO: Storing parton level results
INFO: End Parton
reweight -from_cards
decay_events -from_cards
INFO: storing files of previous run
INFO: Done
quit

Hi,

Looks like that you are using the beta version 3.0.0 and not the stable 2.6.6 version of the code.
I do not reproduce such issue with 2.6.6 (neither our development version 2.6.7).
But I indeed face that issue within 3.0.1.

So my advice would be for you to switch back to the stable release.
I will obviously check what's going on within 3.0.1. Thanks a lot for testing that version and for your bug report.

Cheers,

Olivier

> On 27 Aug 2019, at 12:37, Olivier Mattelaer <email address hidden> wrote:
>
> Question #683402 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/683402
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Can you put the banner? such that I can see which process you are
> looking for and that I know all relevant parameter (mass of which
> particles, scale choice used, width,...)
>
> With that few information I can write a book on all the mistake that can
> happens.
>
> Cheers,
>
> Olivier
>
>> On 27 Aug 2019, at 12:23, FEDERICA giacchino <email address hidden> wrote:
>>
>> New question #683402 on MadGraph5_aMC@NLO:
>> https://answers.launchpad.net/mg5amcnlo/+question/683402
>>
>> Hi,
>>
>> I am working with an ALP model where the alp particle is coupled with electrons (here you can find the model
>> https://www.dropbox.com/sh/w32gh1qfl1ttd4n/AADl9TZb5ZJTMsjk63-vT8sra?dl=0). When the mass of alp is near 16.7 MeV the cross-section has instabilities (the error is larger than cross-section) and the number of events is zero. I have checked everything also analytically. The value of energy beam is 550MeV so the resonance is far from 16.7 MeV.
>>
>> Do you know why I observe this instability?
>>
>> Thanks
>> Federica
>>
>> --
>> You received this question notification because you are an answer
>> contact for MadGraph5_aMC@NLO.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Just to confirm that this is also fix within the future 3.0.2.
Looks like a bug that was fixed in 2.6.5 or 2.6.6 (since 3.0.1 is based on 2.6.4 and was bugged)

Cheers and thanks,

Olivier

Sorry If I bother you again, but even if with the Madgraph 2.6.6 version the instability near 16.7MeV disappeared, at Ma>19.7MeV there is a new instability (no event and error larger than cross-section). Why?

This typically happens when one of the following two conditions happens:
1) singularity of the matrix-element
2) issue within the phase-space integrator.

While I can not rule out the second issue so far. Let me concentrate on the first issue.
When I look at your input parameter, I see that you have a massive electron stable (his width is zero).
But you have an electron propagator within your Feynman Diagram, therefore if that electron can be onshell, you have a singularity that leads to infinite cross-section. I believe that this is your issue. Would that make sense for you?

Cheers,

Olivier

Can you help with this problem?

Provide an answer of your own, or ask FEDERICA giacchino for more information if necessary.

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