Overflow error

Hi,

Looks like a problem when trying to evaluate the strong coupling at the scale of your x1 particle..

My guess is that the mass of that particle is very small (less than 1 GeV). Is this correct?

The way to solve it, is probably to do the computation in the old way.
i.e. to run
Generate x1 > all all
output
Launch -i
calculate_decay_widths

(Choose a fix (high enough) scale in the run_card)

This will create a valid param_card with the decay information needed by Pythia.

Cheers,

Olivier

> On 29 Jun 2017, at 12:38, nabanita ganguly <email address hidden> wrote:
>
> New question #645493 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/645493
>
> Hi mg5 team,
>
> I am trying to study some events of a bsm model. The model file has been generated using Feynrules. The process looks like :
>
> generate p p > x1 x1
>
> where x1 is some bsm particle.
>
> 1) If I work with the default width value ( which I entered by hand in feynrule file and obviously random ), mg5 works fine at parton level. But at pythia level , it is declaring "x1" as a stable particle which is quite strange as all the relevant interaction vertices of possible decays of "x1" exist in couplings.py as well as vertices.py files. The sm part is working fine although.
>
> 2) Now if I set the decay width of "x1" to Auto instead of using the default value , I am getting the following error mesage :
>
> set automatic_html_opening False --no_save
> compute_widths 5100024 5100021 5100030 5100023 --precision_channel=0.01 --body_decay=4.0025 --path=/home/nabanita/MG5_aMC_v2_4_3/PROC_NMUED_UFO_0/Cards/param_card.dat --output=/home/nabanita/MG5_aMC_v2_4_3/PROC_NMUED_UFO_0/Cards/param_card.dat
> Please note that the automatic computation of the width is
> only valid in narrow-width approximation and at tree-level.
> INFO: Get two body decay from FeynRules formula
> Results written to /home/nabanita/MG5_aMC_v2_4_3/PROC_NMUED_UFO_0/Cards/param_card.dat
> INFO: get decay diagram for w1+
> Vertexlist of this model has not been searched.Automatically run the model.find_vertexlist()
> Found 10 stable particles
> Command "generate_events run_01" interrupted in sub-command:
> "set max_npoint_for_channel 0" with error:
> OverflowError : (34, 'Numerical result out of range')
> Please report this bug on https://bugs.launchpad.net/mg5amcnlo
> More information is found in 'MG5_debug'.
> Please attach this file to your report.
>
>
> This is how MG5_debug file looks like :
>
>
> #************************************************************
> #* MadGraph5_aMC@NLO *
> #* *
> #* * * *
> #* * * * * *
> #* * * * * 5 * * * * *
> #* * * * * *
> #* * * *
> #* *
> #* *
> #* VERSION 2.4.3 2016-08-01 *
> #* *
> #* 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 loop_optimized_output True
> set loop_color_flows False
> set gauge unitary
> set complex_mass_scheme False
> set max_npoint_for_channel 0
> Traceback (most recent call last):
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 1011, in onecmd
> return self.onecmd_orig(line, **opt)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 966, in onecmd_orig
> return func(arg, **opt)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madevent_interface.py", line 1992, in do_generate_events
> postcmd=False)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 1037, in exec_cmd
> stop = Cmd.onecmd_orig(current_interface, line, **opt)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 966, in onecmd_orig
> return func(arg, **opt)
>
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madevent_interface.py", line 1992, in do_generate_events
> postcmd=False)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 1037, in exec_cmd
> stop = Cmd.onecmd_orig(current_interface, line, **opt)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 966, in onecmd_orig
> return func(arg, **opt)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madevent_interface.py", line 2664, in do_survey
> self.configure_directory()
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madevent_interface.py", line 3922, in configure_directory
> self.do_treatcards('')
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madevent_interface.py", line 2458, in do_treatcards
> self.check_param_card(pjoin(self.me_dir, 'Cards','param_card.dat'))
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/common_run_interface.py", line 1721, in check_param_card
> self.do_compute_widths('%s %s' % (' '.join(pdg), path))
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/common_run_interface.py", line 1326, in do_compute_widths
> cmd.exec_cmd(line, model=opts['model'])
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 1037, in exec_cmd
> stop = Cmd.onecmd_orig(current_interface, line, **opt)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 966, in onecmd_orig
> return func(arg, **opt)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/master_interface.py", line 331, in do_compute_widths
> return self.cmd.do_compute_widths(self, *args, **opts)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madgraph_interface.py", line 7664, in do_compute_widths
> ), skip_2body=skip_2body)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/master_interface.py", line 319, in do_decay_diagram
> return self.cmd.do_decay_diagram(self, *args, **opts)
> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madgraph_interface.py", line 7922, in do_decay_diagram
> model.find_all_channels(2,generate_abstract=False)
> File "/home/nabanita/MG5_aMC_v2_4_3/mg5decay/decay_objects.py", line 2839, in find_all_channels
> self.running_externals(abs(eval(part.get('mass'))))
> File "/home/nabanita/MG5_aMC_v2_4_3/mg5decay/decay_objects.py", line 2054, in running_externals
> a_out = self.newton1(t, amc, loopnum, 3.)
> File "/home/nabanita/MG5_aMC_v2_4_3/mg5decay/decay_objects.py", line 2113, in newton1
> fp = 1./(a_out**2 * (1. + c1[nf]*a_out))
> OverflowError: (34, 'Numerical result out of range')
>
> MadGraph5_aMC@NLO Options
> ----------------
> complex_mass_scheme : False
> gauge : unitary
> group_subprocesses : Auto
> ignore_six_quark_processes : False
> loop_color_flows : False
> loop_optimized_output : True
> low_mem_multicore_nlo_generation : False
> max_npoint_for_channel : 0
> stdout_level : 20 (user set)
>
> MadEvent Options
> ----------------
> automatic_html_opening : False (user set)
> nb_core : None
> notification_center : True
> run_mode : 2
>
> Configuration Options
> ---------------------
> OLP : MadLoop
> amcfast : amcfast-config
> applgrid : applgrid-config
> auto_update : 7
> cluster_local_path : None
> cluster_nb_retry : 1
> cluster_queue : None (user set)
> cluster_retry_wait : 300
> cluster_size : 100
> cluster_status_update : (600, 30)
> cluster_temp_path : None
> cluster_type : condor
> cpp_compiler : None
> delphes_path : ./Delphes
> eps_viewer : None
> exrootanalysis_path : ./ExRootAnalysis
> f2py_compiler : None
> fastjet : None (user set)
> fortran_compiler : None
> golem : None (user set)
> hepmc_path : None (user set)
> hwpp_path : None (user set)
> lhapdf : lhapdf-config
> madanalysis_path : ./MadAnalysis
> ninja : ./HEPTools/lib
> output_dependencies : external
> pjfry : None (user set)
> pythia-pgs_path : ./pythia-pgs
> pythia8_path : None (user set)
> samurai : None
> syscalc_path : ./SysCalc
> td_path : ./td
> text_editor : None
> thepeg_path : None (user set)
> timeout : 60
> web_browser : None
>
>
> I have absolutely no idea what is going wrong. ANy suggestion from you will be of great help.
>
> My version is 2.4.2
>
>
> Regards,
> Nabanita
>
>
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi,

I can not test without your model, but in principle this patch should fi the problem for
"Auto" mode:

Cheers,

Olivier

=== modified file 'mg5decay/decay_objects.py'
--- mg5decay/decay_objects.py 2017-02-14 15:08:19 +0000
+++ mg5decay/decay_objects.py 2017-06-30 20:49:25 +0000
@@ -2836,8 +2836,13 @@
                 continue

             # Recalculating parameters and coupling constants
- self.running_externals(abs(eval(part.get('mass'))))
- self.running_internals()
+ if (abs(eval(part.get('mass')))) > 0.1:
+ self.running_externals(abs(eval(part.get('mass'))))
+ self.running_internals()
+ else:
+ # if the mass is too low, then the QCD decay will be discarded anyway.
+ # so just forget about the running here
+ logger.info('particle %s has a mass too low to use the mass as the scale for the running of the strong coupling.' % part.get('name'))
             #logger.info("Find 2-body channels of %s" %part.get('name'))
             part.find_channels_nextlevel(self, min_br)

> On 30 Jun 2017, at 20:34, Olivier Mattelaer <email address hidden> wrote:
>
> Hi,
>
> Looks like a problem when trying to evaluate the strong coupling at the scale of your x1 particle..
>
> My guess is that the mass of that particle is very small (less than 1 GeV). Is this correct?
>
> The way to solve it, is probably to do the computation in the old way.
> i.e. to run
> Generate x1 > all all
> output
> Launch -i
> calculate_decay_widths
>
> (Choose a fix (high enough) scale in the run_card)
>
> This will create a valid param_card with the decay information needed by Pythia.
>
> Cheers,
>
> Olivier
>
>
>
>> On 29 Jun 2017, at 12:38, nabanita ganguly <email address hidden> wrote:
>>
>> New question #645493 on MadGraph5_aMC@NLO:
>> https://answers.launchpad.net/mg5amcnlo/+question/645493
>>
>> Hi mg5 team,
>>
>> I am trying to study some events of a bsm model. The model file has been generated using Feynrules. The process looks like :
>>
>> generate p p > x1 x1
>>
>> where x1 is some bsm particle.
>>
>> 1) If I work with the default width value ( which I entered by hand in feynrule file and obviously random ), mg5 works fine at parton level. But at pythia level , it is declaring "x1" as a stable particle which is quite strange as all the relevant interaction vertices of possible decays of "x1" exist in couplings.py as well as vertices.py files. The sm part is working fine although.
>>
>> 2) Now if I set the decay width of "x1" to Auto instead of using the default value , I am getting the following error mesage :
>>
>> set automatic_html_opening False --no_save
>> compute_widths 5100024 5100021 5100030 5100023 --precision_channel=0.01 --body_decay=4.0025 --path=/home/nabanita/MG5_aMC_v2_4_3/PROC_NMUED_UFO_0/Cards/param_card.dat --output=/home/nabanita/MG5_aMC_v2_4_3/PROC_NMUED_UFO_0/Cards/param_card.dat
>> Please note that the automatic computation of the width is
>> only valid in narrow-width approximation and at tree-level.
>> INFO: Get two body decay from FeynRules formula
>> Results written to /home/nabanita/MG5_aMC_v2_4_3/PROC_NMUED_UFO_0/Cards/param_card.dat
>> INFO: get decay diagram for w1+
>> Vertexlist of this model has not been searched.Automatically run the model.find_vertexlist()
>> Found 10 stable particles
>> Command "generate_events run_01" interrupted in sub-command:
>> "set max_npoint_for_channel 0" with error:
>> OverflowError : (34, 'Numerical result out of range')
>> Please report this bug on https://bugs.launchpad.net/mg5amcnlo
>> More information is found in 'MG5_debug'.
>> Please attach this file to your report.
>>
>>
>> This is how MG5_debug file looks like :
>>
>>
>> #************************************************************
>> #* MadGraph5_aMC@NLO *
>> #* *
>> #* * * *
>> #* * * * * *
>> #* * * * * 5 * * * * *
>> #* * * * * *
>> #* * * *
>> #* *
>> #* *
>> #* VERSION 2.4.3 2016-08-01 *
>> #* *
>> #* 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 loop_optimized_output True
>> set loop_color_flows False
>> set gauge unitary
>> set complex_mass_scheme False
>> set max_npoint_for_channel 0
>> Traceback (most recent call last):
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 1011, in onecmd
>> return self.onecmd_orig(line, **opt)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 966, in onecmd_orig
>> return func(arg, **opt)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madevent_interface.py", line 1992, in do_generate_events
>> postcmd=False)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 1037, in exec_cmd
>> stop = Cmd.onecmd_orig(current_interface, line, **opt)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 966, in onecmd_orig
>> return func(arg, **opt)
>>
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madevent_interface.py", line 1992, in do_generate_events
>> postcmd=False)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 1037, in exec_cmd
>> stop = Cmd.onecmd_orig(current_interface, line, **opt)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 966, in onecmd_orig
>> return func(arg, **opt)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madevent_interface.py", line 2664, in do_survey
>> self.configure_directory()
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madevent_interface.py", line 3922, in configure_directory
>> self.do_treatcards('')
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madevent_interface.py", line 2458, in do_treatcards
>> self.check_param_card(pjoin(self.me_dir, 'Cards','param_card.dat'))
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/common_run_interface.py", line 1721, in check_param_card
>> self.do_compute_widths('%s %s' % (' '.join(pdg), path))
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/common_run_interface.py", line 1326, in do_compute_widths
>> cmd.exec_cmd(line, model=opts['model'])
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 1037, in exec_cmd
>> stop = Cmd.onecmd_orig(current_interface, line, **opt)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/extended_cmd.py", line 966, in onecmd_orig
>> return func(arg, **opt)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/master_interface.py", line 331, in do_compute_widths
>> return self.cmd.do_compute_widths(self, *args, **opts)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madgraph_interface.py", line 7664, in do_compute_widths
>> ), skip_2body=skip_2body)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/master_interface.py", line 319, in do_decay_diagram
>> return self.cmd.do_decay_diagram(self, *args, **opts)
>> File "/home/nabanita/MG5_aMC_v2_4_3/madgraph/interface/madgraph_interface.py", line 7922, in do_decay_diagram
>> model.find_all_channels(2,generate_abstract=False)
>> File "/home/nabanita/MG5_aMC_v2_4_3/mg5decay/decay_objects.py", line 2839, in find_all_channels
>> self.running_externals(abs(eval(part.get('mass'))))
>> File "/home/nabanita/MG5_aMC_v2_4_3/mg5decay/decay_objects.py", line 2054, in running_externals
>> a_out = self.newton1(t, amc, loopnum, 3.)
>> File "/home/nabanita/MG5_aMC_v2_4_3/mg5decay/decay_objects.py", line 2113, in newton1
>> fp = 1./(a_out**2 * (1. + c1[nf]*a_out))
>> OverflowError: (34, 'Numerical result out of range')
>>
>> MadGraph5_aMC@NLO Options
>> ----------------
>> complex_mass_scheme : False
>> gauge : unitary
>> group_subprocesses : Auto
>> ignore_six_quark_processes : False
>> loop_color_flows : False
>> loop_optimized_output : True
>> low_mem_multicore_nlo_generation : False
>> max_npoint_for_channel : 0
>> stdout_level : 20 (user set)
>>
>> MadEvent Options
>> ----------------
>> automatic_html_opening : False (user set)
>> nb_core : None
>> notification_center : True
>> run_mode : 2
>>
>> Configuration Options
>> ---------------------
>> OLP : MadLoop
>> amcfast : amcfast-config
>> applgrid : applgrid-config
>> auto_update : 7
>> cluster_local_path : None
>> cluster_nb_retry : 1
>> cluster_queue : None (user set)
>> cluster_retry_wait : 300
>> cluster_size : 100
>> cluster_status_update : (600, 30)
>> cluster_temp_path : None
>> cluster_type : condor
>> cpp_compiler : None
>> delphes_path : ./Delphes
>> eps_viewer : None
>> exrootanalysis_path : ./ExRootAnalysis
>> f2py_compiler : None
>> fastjet : None (user set)
>> fortran_compiler : None
>> golem : None (user set)
>> hepmc_path : None (user set)
>> hwpp_path : None (user set)
>> lhapdf : lhapdf-config
>> madanalysis_path : ./MadAnalysis
>> ninja : ./HEPTools/lib
>> output_dependencies : external
>> pjfry : None (user set)
>> pythia-pgs_path : ./pythia-pgs
>> pythia8_path : None (user set)
>> samurai : None
>> syscalc_path : ./SysCalc
>> td_path : ./td
>> text_editor : None
>> thepeg_path : None (user set)
>> timeout : 60
>> web_browser : None
>>
>>
>> I have absolutely no idea what is going wrong. ANy suggestion from you will be of great help.
>>
>> My version is 2.4.2
>>
>>
>> Regards,
>> Nabanita
>>
>>
>>
>>
>> --
>> You received this question notification because you are an answer
>> contact for MadGraph5_aMC@NLO.
>

Hi,

Thanks a lot for looking into the matter.

## My guess is that the mass of the Particle is very small ( less than 1GeV). Is this correct?

Not really. The mass of "x1" is around say 500 GeV.

I tried the method you suggested. It seems to work. I still have some doubts

1) It I want to calculate decay width of multiple particles (all bsm and of the same model) in the same param_card , what to be done?

2) the overflow error is still there even after the changes in the decays.py file. I have around 26new particles in my model. I was just wondering whether this many number is causing any trouble.

3) If I follow step 1) and run Pythia using the generated param_card.dat, mg5 gets stuck after "running Pythia" command.

Regards,
Nabanita

Sorry forgot to mention I can email you the model file if you want. In that case please provide me the id. Thank u.

Having the model would be useful indeed.
You can send it to <email address hidden>

Cheers,

Olivier

> On 1 Jul 2017, at 16:23, nabanita ganguly <email address hidden> wrote:
>
> Question #645493 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/645493
>
> nabanita ganguly posted a new comment:
> Sorry forgot to mention I can email you the model file if you want. In
> that case please provide me the id. Thank u.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi,

The problem is that your model does not set the mass of the light quark to zero.
This is technically inconsistent with the pdf hyppothesis, but more importantly, this slows down the computation by huge factor:
See this thread: https://answers.launchpad.net/mg5amcnlo/+faq/2312
to see how to solve such problem if you do not have access to FeynRules.

When the above problem would be solve then your problem should be as well.

Cheers,

Olivier

PS: I do not have any particles named x1 in your model
PPS: If you need those mass for some physics reason, another way to fix this is:
=== modified file 'mg5decay/decay_objects.py'
--- mg5decay/decay_objects.py 2017-02-14 15:08:19 +0000
+++ mg5decay/decay_objects.py 2017-07-01 20:30:15 +0000
@@ -1992,6 +1992,9 @@
     def running_externals(self, q, loopnum=2):
         """ Recalculate external parameters at the given scale. """

+ if q < 0.5:
+ return
+
         # Raise error for wrong type of q
         if not isinstance(q, int) and not isinstance(q, long) and \
                 not isinstance(q, float):

Thank you so much Olivier for ur help.

Thanks Olivier Mattelaer, that solved my question.

Hi,

I am really sorry for reopening this question. I am facing another problem in the same model when trying to run in madgraph.
The problem is as follows :

I have a particle named G1 (mass mg1) whose decay modes I want to study. Now this fellow can only decay into quark pairs like Q1 q where q is the usual SM quark and Q1 is a bsm quark. Q1 has a mass mQ1.

When mg1 > mQ1 , result is as per expectation. But when mg1 < mQ1 , mg5 is returning the decay width of G1 as zero and hence it remains as a stable particle!! This is very strange as I expect G1 to undergo three-body decay in this case (via offshell Q1). But somehow mg5 is unable to generate 3-body decay of G1.

Another observation is that this is not the case with SM part i.e. SM particles can appear as offshell in a decay chain. Therefore I suspect this is something to do with the bsm part.

Could you please suggest what's going wrong here?

My version is 2.4.2

Hi,

Did you see any warning related to the QCD scale when the code computes the width?
We have a cut off in MG for the case where the width are below the QCD scale since in that case, the particle will hadronize before the actual decay.
In that case we set the equivalent partial width to zero since we do not know how to compute such type of decay.

Cheers,

Olivier

> On 4 Jul 2017, at 12:27, nabanita ganguly <email address hidden> wrote:
>
> Question #645493 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/645493
>
> Status: Solved => Open
>
> nabanita ganguly is still having a problem:
> Hi,
>
> I am really sorry for reopening this question. I am facing another problem in the same model when trying to run in madgraph.
> The problem is as follows :
>
> I have a particle named G1 (mass mg1) whose decay modes I want to study.
> Now this fellow can only decay into quark pairs like Q1 q where q is the
> usual SM quark and Q1 is a bsm quark. Q1 has a mass mQ1.
>
> When mg1 > mQ1 , result is as per expectation. But when mg1 < mQ1 , mg5
> is returning the decay width of G1 as zero and hence it remains as a
> stable particle!! This is very strange as I expect G1 to undergo three-
> body decay in this case (via offshell Q1). But somehow mg5 is unable to
> generate 3-body decay of G1.
>
> Another observation is that this is not the case with SM part i.e. SM
> particles can appear as offshell in a decay chain. Therefore I suspect
> this is something to do with the bsm part.
>
> Could you please suggest what's going wrong here?
>
> My version is 2.4.2
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi,

Thank you so much for the quick response.

Yes I am getting the following warning :

partial width of particle g1 lower than QCD scale:1.8491991012e-07. Set it to zero. ((-5100024, -3, 4))
partial width of particle g1 lower than QCD scale:1.8416992885e-07. Set it to zero. ((-2, 1, 5100024))
partial width of particle g1 lower than QCD scale:1.8412988268e-07. Set it to zero. ((-5100024, -1, 2))
partial width of particle g1 lower than QCD scale:1.83799890921e-07. Set it to zero. ((-4, 3, 5100024))
partial width of particle g1 lower than QCD scale:1.06669963387e-07. Set it to zero. ((-2, 2, 5100022))
partial width of particle g1 lower than QCD scale:1.06389965663e-07. Set it to zero. ((-4, 4, 5100022))
partial width of particle g1 lower than QCD scale:7.57279719804e-08. Set it to zero. ((-2, 2, 5100023))
partial width of particle g1 lower than QCD scale:7.56199746776e-08. Set it to zero. ((-4, 4, 5100023))
partial width of particle g1 lower than QCD scale:7.56019751271e-08. Set it to zero. ((-1, 1, 5100023))
partial width of particle g1 lower than QCD scale:7.55819803434e-08. Set it to zero. ((-3, 3, 5100023))
partial width of particle g1 lower than QCD scale:5.8264983572e-08. Set it to zero. ((-5, 5, 5100023))
partial width of particle g1 lower than QCD scale:3.1248988457e-08. Set it to zero. ((-1, 1, 5100022))
partial width of particle g1 lower than QCD scale:3.10629931021e-08. Set it to zero. ((-3, 3, 5100022))
partial width of particle g1 lower than QCD scale:2.79009871642e-08. Set it to zero. ((-5, 5, 5100022))
partial width of particle g1 lower than QCD scale:3.51009913139e-09. Set it to zero. ((-5100024, -1, 4))
partial width of particle g1 lower than QCD scale:3.4945985751e-09. Set it to zero. ((-2, 3, 5100024))
partial width of particle g1 lower than QCD scale:3.48379884481e-09. Set it to zero. ((-5100024, -3, 2))
partial width of particle g1 lower than QCD scale:3.48099844305e-09. Set it to zero. ((-4, 1, 5100024))

So if I understand properly final states in two cases (mG1 > mQ1 and mG1 < mQ1 ) will be very different from each other e.g. in the first case one can easily have multiple jets whereas in the later it can be one. Is it ok to work with that? or is there some way to calculate the 3-body width?

Best,
Nabanita

Hi,

As you can see, the three body width are actually computed. However you can not really trust such number since the computation is done in perturbation theory and the result clearly show that the particle should hadronize before such type of decay.
Consequently, one should exxpect to observe new type of hadron as final state.
Such kind of computation should be technically done via some latice QCD. But I do not know any tools available for that (neither if such computation can be done or not)

Cheers,

Olivier