Z to three gamma

Hi,

This decay is a loop-induced decay and not a tree-level one.
Therefore you need to use the loop-induced syntax and a model which is able to handle such loop.
The syntax is therefore
import model loop_qcd_qed_sm
generate p p > z > a a a [noborn=QED]

Cheers,

Olivier

> On Jul 5, 2016, at 19:57, Jack Bargemann <email address hidden> wrote:
>
> New question #296019 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/296019
>
> I am trying to simulate Z to gamma gamma gamma decay. The branching ratio is predicted by the standard model to be 5.4*10^-10. When I try to simulate this in MadGraph5 using the sm model "generate p p > Z > a a a", I receive the following error: "NoDiagramException : No amplitudes generated from process . . . Please enter a valid process"
>
> Am I doing something wrong, or does this MadGraph model not include this decay?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

I have imported the model and generated the events as suggested. I set the number of events to generate at 10, but when I try to launch the simulation, the runtime is quite long. I have tried multiple times, waiting over two hours for ten events, but it still has not completed. Is this normal, or is there something I need to fix?

MG5_aMC>launch Z
************************************************************
* *
* W E L C O M E to *
* M A D G R A P H 5 _ a M C @ N L O *
* M A D E V E N T *
* *
* * * *
* * * * * *
* * * * * 5 * * * * *
* * * * * *
* * * *
* *
* VERSION 2.4.2 2016-06-10 *
* *
* The MadGraph5_aMC@NLO Development Team - Find us at *
* https://server06.fynu.ucl.ac.be/projects/madgraph *
* *
* Type 'help' for in-line help. *
* *
************************************************************
INFO: load configuration from /home/jack/Downloads/MG5_aMC_v2_4_2/bin/Z/Cards/me5_configuration.txt
INFO: load configuration from /home/jack/Downloads/MG5_aMC_v2_4_2/input/mg5_configuration.txt
INFO: load configuration from /home/jack/Downloads/MG5_aMC_v2_4_2/bin/Z/Cards/me5_configuration.txt
Using default text editor "vi". Set another one in ./input/mg5_configuration.txt
generate_events run_01
The following switches determine which programs are run:
 1 Run the pythia shower/hadronization: pythia=OFF
 2 Run PGS as detector simulator: pgs=OFF
 3 Run Delphes as detector simulator: delphes=NOT INSTALLED
 4 Decay particles with the MadSpin module: madspin=OFF
 5 Add weights to the events based on changing model parameters: reweight=OFF
  Either type the switch number (1 to 5) to change its default setting,
  or set any switch explicitly (e.g. type 'madspin=ON' at the prompt)
  Type '0', 'auto', 'done' or just press enter when you are done.
 [0, 1, 2, 4, 5, auto, done, pythia=ON, pythia=OFF, ... ][60s to answer]
>0
Do you want to edit a card (press enter to bypass editing)?
  1 / param : param_card.dat
  2 / run : run_card.dat
  3 / MadLoopParams : MadLoopParams.dat
  9 / 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, MadLoopParams, 9, enter path, ... ][60s to answer]
>2
open /home/jack/Downloads/MG5_aMC_v2_4_2/bin/Z/Cards/run_card.dat
Do you want to edit a card (press enter to bypass editing)?
  1 / param : param_card.dat
  2 / run : run_card.dat
  3 / MadLoopParams : MadLoopParams.dat
  9 / 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, MadLoopParams, 9, enter path, ... ]
>0
Generating 10 events with run name run_01
survey run_01
INFO: compile directory
initMadLoop -r -f
Initializing MadLoop loop-induced matrix elements (this can take some time)...
MadLoop initialization finished.
compile Source Directory
Using random number seed offset = 21
INFO: Running Survey
Creating Jobs
Working on SubProcesses
INFO: P0_qq_aaa
INFO: Idle: 1, Running: 0, Completed: 0 [ current time: 04h09 ]
INFO: Idle: 0, Running: 1, Completed: 0 [ 5m 0s ]

Hi,

The first stage of the computation correspond to have a 5% estimate of the cross-section.
This stage is independent of the number of events requested for generation.
So it is indeed quite inefficient to ask for a very small number of events.

Loop-induced processes are extremely complex to integrate and each phase-space point can takes a lot of time since this a loop computation.
Additionally the result of the loop-computation can sometimes be pledged by huge numerical inaccuracy forcing to sometimes evaluates the matrix element
in quadruple precision (which slows down the code by a factor 100).

So you should not expect to have anything fast for a 2 > 3 final state. Those are typically possible on quad core laptop and/or small size cluster
On my computer I have the following log/speed:

> Working on SubProcesses
> INFO: P0_qq_aaa
> INFO: Idle: 0, Running: 4, Completed: 0 [ current time: 20h02 ]
> INFO: Idle: 0, Running: 3, Completed: 1 [ 1m 30s ]
> INFO: P0_qq_aaa/G4 is at 3.16e-06 +- 2.25e-06 pb. Now submitting iteration #2.
> INFO: P0_qq_aaa/G1 is at 2.88e-06 +- 2.04e-06 pb. Now submitting iteration #2.
> INFO: Idle: 0, Running: 3, Completed: 7 [ 3m 10s ]
> INFO: P0_qq_aaa/G4 is at 6.4e-06 +- 2.63e-06 pb. Now submitting iteration #3.
> INFO: Idle: 1, Running: 2, Completed: 11 [ 3m 14s ]
> INFO: P0_qq_aaa/G1 is at 1.54e-06 +- 2.67e-07 pb. Now submitting iteration #3.

> INFO: Idle: 0, Running: 3, Completed: 13 [ 6m 22s ]
> INFO: Idle: 1, Running: 1, Completed: 15 [ 6m 25s ]
> INFO: P0_qq_aaa/G4 is at 2.55e-06 +- 9.92e-07 pb. Now submitting iteration #4.
> INFO: Idle: 1, Running: 2, Completed: 17 [ 6m 28s ]
> INFO: P0_qq_aaa/G1 is at 2.26e-06 +- 5.11e-07 pb. Now submitting iteration #4.

Now this speed can highly depend of the cut that you used since if you decrease the cut, you can need much more often the quadruple precision meaning
that you can have a code 100 times slower (times the factor of 4 due to the difference of computer).
So depending of your cut it can go up to 6h before the first update on your machine.

Cheers,

Olivier

> On Jul 6, 2016, at 19:13, Jack Bargemann <email address hidden> wrote:
>
> Question #296019 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/296019
>
> Status: Answered => Open
>
> Jack Bargemann is still having a problem:
> I have imported the model and generated the events as suggested. I set
> the number of events to generate at 10, but when I try to launch the
> simulation, the runtime is quite long. I have tried multiple times,
> waiting over two hours for ten events, but it still has not completed.
> Is this normal, or is there something I need to fix?
>
> MG5_aMC>launch Z
> ************************************************************
> * *
> * W E L C O M E to *
> * M A D G R A P H 5 _ a M C @ N L O *
> * M A D E V E N T *
> * *
> * * * *
> * * * * * *
> * * * * * 5 * * * * *
> * * * * * *
> * * * *
> * *
> * VERSION 2.4.2 2016-06-10 *
> * *
> * The MadGraph5_aMC@NLO Development Team - Find us at *
> * https://server06.fynu.ucl.ac.be/projects/madgraph *
> * *
> * Type 'help' for in-line help. *
> * *
> ************************************************************
> INFO: load configuration from /home/jack/Downloads/MG5_aMC_v2_4_2/bin/Z/Cards/me5_configuration.txt
> INFO: load configuration from /home/jack/Downloads/MG5_aMC_v2_4_2/input/mg5_configuration.txt
> INFO: load configuration from /home/jack/Downloads/MG5_aMC_v2_4_2/bin/Z/Cards/me5_configuration.txt
> Using default text editor "vi". Set another one in ./input/mg5_configuration.txt
> generate_events run_01
> The following switches determine which programs are run:
> 1 Run the pythia shower/hadronization: pythia=OFF
> 2 Run PGS as detector simulator: pgs=OFF
> 3 Run Delphes as detector simulator: delphes=NOT INSTALLED
> 4 Decay particles with the MadSpin module: madspin=OFF
> 5 Add weights to the events based on changing model parameters: reweight=OFF
> Either type the switch number (1 to 5) to change its default setting,
> or set any switch explicitly (e.g. type 'madspin=ON' at the prompt)
> Type '0', 'auto', 'done' or just press enter when you are done.
> [0, 1, 2, 4, 5, auto, done, pythia=ON, pythia=OFF, ... ][60s to answer]
>> 0
> Do you want to edit a card (press enter to bypass editing)?
> 1 / param : param_card.dat
> 2 / run : run_card.dat
> 3 / MadLoopParams : MadLoopParams.dat
> 9 / 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, MadLoopParams, 9, enter path, ... ][60s to answer]
>> 2
> open /home/jack/Downloads/MG5_aMC_v2_4_2/bin/Z/Cards/run_card.dat
> Do you want to edit a card (press enter to bypass editing)?
> 1 / param : param_card.dat
> 2 / run : run_card.dat
> 3 / MadLoopParams : MadLoopParams.dat
> 9 / 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, MadLoopParams, 9, enter path, ... ]
>> 0
> Generating 10 events with run name run_01
> survey run_01
> INFO: compile directory
> initMadLoop -r -f
> Initializing MadLoop loop-induced matrix elements (this can take some time)...
> MadLoop initialization finished.
> compile Source Directory
> Using random number seed offset = 21
> INFO: Running Survey
> Creating Jobs
> Working on SubProcesses
> INFO: P0_qq_aaa
> INFO: Idle: 1, Running: 0, Completed: 0 [ current time: 04h09 ]
> INFO: Idle: 0, Running: 1, Completed: 0 [ 5m 0s ]
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.