MadGraph5_aMC@NLO

Multiple runs with different centre of mass energies

Asked by H O Lim

Dear Madgraph team,

Hi, I am currently doing a project that requires varying the centre of mass energy of a scattering process and getting the cross section. I am just wondering is there a way to just edit the ebeam1 and ebeam2 and do multiple run on the madgraph without generating the whole process again which will result in outputting a new folder?

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
Last query:
Last reply:
Revision history for this message
Best Olivier Mattelaer (olivier-mattelaer) said : 		#1

Did you look at the following link?
you can also do the same without the first two line of the examples if that directory already exists.
(in that case you can run such script from ./bin/madevent PATH if you do not specify the directory for the first "launch" command.)

For modifying the energy beam, you can use
set ebeam1 XXX
set ebeam2 XXX
or
set ebeam XXX #modify both to XXX
set LHC 14. # 14 TeV LHC
set lep 200. # 200GeV lep

Olivier Mattelaer suggests this article as an answer to your question:
FAQ #2186: “How to script MG5 run?”.

Revision history for this message
H O Lim (accel6076) said : 		#2

Thanks Olivier Mattelaer, that solved my question.

Revision history for this message
Antonio Sandroni (antoniosandroni) said : 		#3

Hi, what does set LHC and set lep stand for? If i change the beam energy with set ebeam and the beams are lepton do i need to do set lep?
Thanks

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#4

so "set LHC" and "set lep" are shortcut.
they both have their dedicated help message:
>help lep
 INFO: *** HELP MESSAGE ***
syntax: set lep VALUE:
      Set for a electron-positron collision with that given center of mass energy (in GeV)
INFO: *** END HELP ***

syntax: set lhc VALUE:
      Set for a proton-proton collision with that given center of mass energy (in TeV)
INFO: *** END HELP ***

and when you do use them, they say explicitely what they do for the run_card:

>set lhc 13
INFO: modify parameter lpp1 of the run_card.dat to 1
INFO: modify parameter lpp2 of the run_card.dat to 1
INFO: modify parameter ebeam1 of the run_card.dat to 6500.0
INFO: modify parameter ebeam2 of the run_card.dat to 6500.0

>set lep 500
INFO: modify parameter lpp1 of the run_card.dat to 0
INFO: modify parameter lpp2 of the run_card.dat to 0
INFO: modify parameter ebeam1 of the run_card.dat to 250.0
INFO: modify parameter ebeam2 of the run_card.dat to 250.0

> If i change the beam energy with set ebeam and the beams are lepton do i need to do set lep?

as this is a shortcut, you certainly not need to use it, you can always avoid it.
Now for lepton, in general one has to set lpp1/2 to zero and that can be doin via the shortcut or via dedicated command.
(Now the default value for lpp1/lpp2 are likely being set to zero anyway)

Cheers,

Olivier