the width of particle is too small for an s-channel

Asked by mehdirahmani on 2019-05-23

Hi,

I have a scalar particle with a width of 2e-14 (1cm displacement). I am trying to generate some events in MadGraph VERSION 2.6.5 and I get the following error:

ERROR: The width of particle 5000512 is too small for an s-channel resonance (2e-14). If you have this particle in an s-channel, this is likely to create numerical instabilities .

INFO: Update the dependent parameter of the param_card.dat

ERROR: The width of particle 5000512 is too small for an s-channel resonance (2e-14). If you have this particle in an s-channel, this is likely to create numerical instabilities .

I have added the lines:
1e-14 = small_width_treatment
and
10 = time_of_flight (because in the run_card it says the unit of this variable is mm)
But still I get the errors!

What else can be done here to address this error.

Thanks,

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
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Last query:
2019-05-28
Last reply:
2019-05-28

HI,

They are indeed a bug with that message. It is always printed to the screen even if the
small_width_treatment is set to a correct value (i.e. bigger than 1e-10).
The next version should correctly mute that message.

Now setting the small_width_treatment to 1e-14 should indeed raise that error (even in the next version)
since you basically request to keep such small width for the computation of the matrix-element which indeed leads to numerical unstabilities.
I would advise to keep the default value of small_width_treatment. The code will then use a fake width for the phase-space integration (you will get a warning due to that) which will prevent any numerical issues.
More details are given here:
https://answers.launchpad.net/mg5amcnlo/+faq/3053

Cheers,

Olivier

> On 23 May 2019, at 21:37, mehdirahmani <email address hidden> wrote:
>
> New question #681033 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/681033
>
> Hi,
>
> I have a scalar particle with a width of 2e-14 (1cm displacement). I am trying to generate some events in MadGraph VERSION 2.6.5 and I get the following error:
>
> ERROR: The width of particle 5000512 is too small for an s-channel resonance (2e-14). If you have this particle in an s-channel, this is likely to create numerical instabilities .
>
> INFO: Update the dependent parameter of the param_card.dat
>
> ERROR: The width of particle 5000512 is too small for an s-channel resonance (2e-14). If you have this particle in an s-channel, this is likely to create numerical instabilities .
>
> I have added the lines:
> 1e-14 = small_width_treatment
> and
> 10 = time_of_flight (because in the run_card it says the unit of this variable is mm)
> But still I get the errors!
>
> What else can be done here to address this error.
>
> Thanks,
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

mehdirahmani (mehdirahmani) said : #2

Thank you, Oliver!
What is the default value for small_width_treatment? How about time_of_flight?

Hi,

You can use the
set small_width_treatment default
command to know that:
> Do you want to edit a card (press enter to bypass editing)?
> /------------------------------------------------------------\
> | 1. param : param_card.dat |
> | 2. run : run_card.dat |
> | 3. plot : plot_card.dat |
> \------------------------------------------------------------/
> you can also
> - enter the path to a valid card or banner.
> - use the 'set' command to modify a parameter directly.
> The set option works only for param_card and run_card.
> Type 'help set' for more information on this command.
> - call an external program (ASperGE/MadWidth/...).
> Type 'help' for the list of available command
> [0, done, 1, param, 2, run, 3, plot, enter path]
> >set small_width_treatment default
> INFO: modify parameter small_width_treatment of the run_card.dat to 1e-06

> How about time_of_flight?

This is just a threshold below which displaced vertex information will not be written in the lhef file.
So you can put the value that you want for that.

Cheers,

Olivier

> On 23 May 2019, at 22:52, mehdirahmani <email address hidden> wrote:
>
> Question #681033 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/681033
>
> Status: Answered => Open
>
> mehdirahmani is still having a problem:
> Thank you, Oliver!
> What is the default value for small_width_treatment? How about time_of_flight?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

mehdirahmani (mehdirahmani) said : #4

Thank you for your help!

I tried to add the line " set small_width_treatment default " and in my run_card.dat and " -1 = time_of_flight " but I still get the following errors in MG5_aMC_v2_6_5:

WARNING: Particle 5000512 will use a fake width ( 2e-06 instead of 2e-14 ).
Cross-section will be rescaled according to NWA if needed.To force exact treatment reduce the value of 'small_width_treatment' parameter of the run_card
INFO: Update the dependent parameter of the param_card.dat
ERROR: The width of particle 5000512 is too small for an s-channel resonance (2e-14). If you have this particle in an s-channel, this is likely to create numerical instabilities .

Generating 10 events with run name run_02
survey run_02
INFO: compile directory
Failed to open connection to "session" message bus: /bin/dbus-launch terminated abnormally without any error message
Starting a11y dbus service...

ERROR: The width of particle 5000512 is too small for an s-channel resonance (2e-14). If you have this particle in an s-channel, this is likely to create numerical instabilities .
compile Source Directory

Failed to launch bus: Failed to connect to session busError detected in "generate_events "
write debug file /home/merahman/MC/CMSSW_9_3_9_patch1/MadGraph/MG5_aMC_v2_6_5/DMsimp_s_spin1/run_02_tag_1_debug.log
If you need help with this issue please contact us on https://answers.launchpad.net/mg5amcnlo
MadGraph5Error : A compilation Error occurs when trying to compile /home/merahman/MC/CMSSW_9_3_9_patch1/MadGraph/MG5_aMC_v2_6_5/DMsimp_s_spin1/Source.
 The compilation fails with the following output message:
     gfortran -O -w -fbounds-check -fPIC -ffixed-line-length-132 -c -o combine_events.o combine_events.f
     gfortran -o ../bin/internal/combine_events combine_events.o rw_events.o ranmar.o kin_functions.o open_file.o rw_routines.o alfas_functions.o setrun.o -L../lib/ -lmodel -lpdf -lstdc++ -lbias
     /usr/bin/ld: BFD version 2.20.51.0.2-5.48.el6_10.1 20100205 internal error, aborting at reloc.c line 443 in bfd_get_reloc_size

     /usr/bin/ld: Please report this bug.

     collect2: ld returned 1 exit status
     make: *** [../bin/internal/combine_events] Error 1

 Please try to fix this compilations issue and retry.
 Help might be found at https://answers.launchpad.net/mg5amcnlo.
 If you think that this is a bug, you can report this at https://bugs.launchpad.net/mg5amcnlo
quit
INFO:
[merahman@login02 DMsimp_s_spin1]$ Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "canberra-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "canberra-gtk-module"
[merahman@login02 DMsimp_s_spin1]$ Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "canberra-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "canberra-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "canberra-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "canberra-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "canberra-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "canberra-gtk-module"
mozilla::detail::MutexImpl::~MutexImpl: pthread_mutex_destroy failed: Device or resource busy
[Parent 3470923, Gecko_IOThread] WARNING: pipe error (127): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
[Parent 3470923, Gecko_IOThread] WARNING: pipe error (140): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
[Parent 3470923, Gecko_IOThread] WARNING: pipe error (134): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
[Parent 3470923, Gecko_IOThread] WARNING: pipe error (133): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
[Parent 3470923, Gecko_IOThread] WARNING: pipe error (131): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
[Parent 3470923, Gecko_IOThread] WARNING: pipe error (128): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
[Parent 3470923, Gecko_IOThread] WARNING: pipe error (126): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342

But When I try it in MG5_aMC_v2_4_2 I do not get any errors. Is version MG5_aMC_v2_4_2 actually changing the width to a fake width without telling me? Should I try higher versions of MadGraph?

Hi,

This seems unrelated to the width substitiution.
Looks like that you face an internal ld error.

Which version of gfortran/gcc/ld are you using?
Can you test another one?
Did you use the same gcc/ld version for 2.4.2?

2.4.2 is so old, that I have no clue what is inside anymore. But it certainly does not have any trick for the width. (I doubt that it has even a message to warn the user that they will have issues with such old version, I would expect MG5aMC to just return random number when facing too small width (without any warning of any kind)

Cheers,

Olivier

> On 24 May 2019, at 17:02, mehdirahmani <email address hidden> wrote:
>
> Question #681033 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/681033
>
> Status: Answered => Open
>
> mehdirahmani is still having a problem:
> Thank you for your help!
>
> I tried to add the line " set small_width_treatment default " and in my
> run_card.dat and " -1 = time_of_flight " but I still get the following
> errors in MG5_aMC_v2_6_5:
>
> WARNING: Particle 5000512 will use a fake width ( 2e-06 instead of 2e-14 ).
> Cross-section will be rescaled according to NWA if needed.To force exact treatment reduce the value of 'small_width_treatment' parameter of the run_card
> INFO: Update the dependent parameter of the param_card.dat
> ERROR: The width of particle 5000512 is too small for an s-channel resonance (2e-14). If you have this particle in an s-channel, this is likely to create numerical instabilities .
>
> Generating 10 events with run name run_02
> survey run_02
> INFO: compile directory
> Failed to open connection to "session" message bus: /bin/dbus-launch terminated abnormally without any error message
> Starting a11y dbus service...
>
> ERROR: The width of particle 5000512 is too small for an s-channel resonance (2e-14). If you have this particle in an s-channel, this is likely to create numerical instabilities .
> compile Source Directory
>
> Failed to launch bus: Failed to connect to session busError detected in "generate_events "
> write debug file /home/merahman/MC/CMSSW_9_3_9_patch1/MadGraph/MG5_aMC_v2_6_5/DMsimp_s_spin1/run_02_tag_1_debug.log
> If you need help with this issue please contact us on https://answers.launchpad.net/mg5amcnlo
> MadGraph5Error : A compilation Error occurs when trying to compile /home/merahman/MC/CMSSW_9_3_9_patch1/MadGraph/MG5_aMC_v2_6_5/DMsimp_s_spin1/Source.
> The compilation fails with the following output message:
> gfortran -O -w -fbounds-check -fPIC -ffixed-line-length-132 -c -o combine_events.o combine_events.f
> gfortran -o ../bin/internal/combine_events combine_events.o rw_events.o ranmar.o kin_functions.o open_file.o rw_routines.o alfas_functions.o setrun.o -L../lib/ -lmodel -lpdf -lstdc++ -lbias
> /usr/bin/ld: BFD version 2.20.51.0.2-5.48.el6_10.1 20100205 internal error, aborting at reloc.c line 443 in bfd_get_reloc_size
>
> /usr/bin/ld: Please report this bug.
>
> collect2: ld returned 1 exit status
> make: *** [../bin/internal/combine_events] Error 1
>
> Please try to fix this compilations issue and retry.
> Help might be found at https://answers.launchpad.net/mg5amcnlo.
> If you think that this is a bug, you can report this at https://bugs.launchpad.net/mg5amcnlo
> quit
> INFO:
> [merahman@login02 DMsimp_s_spin1]$ Gtk-Message: Failed to load module "pk-gtk-module"
> Gtk-Message: Failed to load module "canberra-gtk-module"
> Gtk-Message: Failed to load module "pk-gtk-module"
> Gtk-Message: Failed to load module "canberra-gtk-module"
> [merahman@login02 DMsimp_s_spin1]$ Gtk-Message: Failed to load module "pk-gtk-module"
> Gtk-Message: Failed to load module "canberra-gtk-module"
> Gtk-Message: Failed to load module "pk-gtk-module"
> Gtk-Message: Failed to load module "canberra-gtk-module"
> Gtk-Message: Failed to load module "pk-gtk-module"
> Gtk-Message: Failed to load module "canberra-gtk-module"
> Gtk-Message: Failed to load module "pk-gtk-module"
> Gtk-Message: Failed to load module "canberra-gtk-module"
> Gtk-Message: Failed to load module "pk-gtk-module"
> Gtk-Message: Failed to load module "canberra-gtk-module"
> Gtk-Message: Failed to load module "pk-gtk-module"
> Gtk-Message: Failed to load module "canberra-gtk-module"
> mozilla::detail::MutexImpl::~MutexImpl: pthread_mutex_destroy failed: Device or resource busy
> [Parent 3470923, Gecko_IOThread] WARNING: pipe error (127): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
> [Parent 3470923, Gecko_IOThread] WARNING: pipe error (140): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
> [Parent 3470923, Gecko_IOThread] WARNING: pipe error (134): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
> [Parent 3470923, Gecko_IOThread] WARNING: pipe error (133): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
> [Parent 3470923, Gecko_IOThread] WARNING: pipe error (131): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
> [Parent 3470923, Gecko_IOThread] WARNING: pipe error (128): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
> [Parent 3470923, Gecko_IOThread] WARNING: pipe error (126): Connection reset by peer: file /builddir/build/BUILD/firefox-60.6.1/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 342
>
>
> But When I try it in MG5_aMC_v2_4_2 I do not get any errors. Is version MG5_aMC_v2_4_2 actually changing the width to a fake width without telling me? Should I try higher versions of MadGraph?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

mehdirahmani (mehdirahmani) said : #6

Hi Oliver,

For MG5_aMC_v2_6_5:
gcc (GCC) 6.3.0

For MG5_aMC_v2_4_2:
gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-36)

Am I using incompatible version of gcc?

Thanks,

I but that your issue is with your installation of 6.3.0.
Can you use 4.8.5 with r MG5_aMC_v2_6_5 (or any other version)

Cheers,

Olivier

> On 28 May 2019, at 16:17, mehdirahmani <email address hidden> wrote:
>
> Question #681033 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/681033
>
> Status: Answered => Open
>
> mehdirahmani is still having a problem:
> Hi Oliver,
>
> For MG5_aMC_v2_6_5:
> gcc (GCC) 6.3.0
>
> For MG5_aMC_v2_4_2:
> gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-36)
>
> Am I using incompatible version of gcc?
>
> Thanks,
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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