How to use lab frame elmax cut?

Hi,

You have two solutions:
1) apply the cut on the generated events. (outside our framework)
One simple way of doing that is to write a small python code following the example present at the end of the file/script
madgraph/various/lhe_parser.py

2) implement your own cut by implementing it directly in SubProcesses/cuts.f
You obviously have to implement the boost first since the momenta in that file are in the com frame.
Be carefull to not reuse the variable from the run_card since those are used in other place of the code for phase-space optimisation.

Cheers,

Olivier

> On Aug 25, 2016, at 06:17, Li <email address hidden> wrote:
>
> New question #363782 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/363782
>
> Hi,
>
> In the run_card.dat, I find:
>
> # 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
> #*********************************************************************
>
> The energy cut is in com frame , but I find some use it in lab frame. So how can I set it? Like
>
> # Minimum and maximum E's (in the lab frame) *
> #*********************************************************************
> 0 = ej ! minimum E for the jets
> 0 = eb ! minimum E for the b
> 0 = ea ! minimum E for the photons
> 0 = el ! minimum E for the charged leptons
> 1d5 = ejmax ! maximum E for the jets
> 1d5 = ebmax ! maximum E for the b
> 1d5 = eamax ! maximum E for the photons
> 1d5 = elmax ! maximum E for the charged leptons
> #*********************************************************************
>
>
> Best,
> Li
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,

  Thanks for your solutions.

  The first solution isn't work because in my process the cut on lepton energy is very serious. So if I want to use first solution and get enough events after cuts , I need to generate more than 10^9 events which are too huge.

  And as my question shows, some one showed me his run card which is default in lab frame. And I find in MG5/tests/input_files/run_card_ee.dat , it's cuts are default in lab frame. So I guess we can apply lab frame cuts just in run_card.dat.

Best,
Li

Hi Li,

> And as my question shows, some one showed me his run card which is
> default in lab frame.

In some very old version of the code, the comment about the frame
in the run_card was just wrong and the code was still performing the cut in the com frame and not in the lab frame.
Whatever the comment in the run_card was saying.
The run_card that we use for the ee test has indeed the wrong comment (which does not impact at all our test routine)

The confusion obviously came from the fact that this is a typical e+ e- cut where both frame are identical (in general)

Cheers,

Olivier

> On Aug 25, 2016, at 09:37, Li <email address hidden> wrote:
>
> Question #363782 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/363782
>
> Li posted a new comment:
> Hi Olivier,
>
> Thanks for your solutions.
>
> The first solution isn't work because in my process the cut on lepton
> energy is very serious. So if I want to use first solution and get
> enough events after cuts , I need to generate more than 10^9 events
> which are too huge.
>
> And as my question shows, some one showed me his run card which is
> default in lab frame. And I find in
> MG5/tests/input_files/run_card_ee.dat , it's cuts are default in lab
> frame. So I guess we can apply lab frame cuts just in run_card.dat.
>
>
> Best,
> Li
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,

  Thanks a lot. Let me discuss with the man who give me a very nice plot about energy cut in lab frame. Maybe he changed something himself.

> this is a typical e+ e- cut where both frame are identical (in general)

  This remind me that my process, the c.o.m frame and lab frame are identical, my process is:
  e e > t t , ( t > w b , w > vl l ) , ( t > w b , w > q q )

  where q = u c d s

  I wonder the cut elmax are added on ee c.o.m frame or in rest w boson's c.o.m frame? If it's added in ee c.o.m frame, the result should be the same to added on lab frame.

  But my result is that, before elmax=10.0 and after, the result almost no change.

Best,
Li

Thanks Olivier Mattelaer, that solved my question.

Hi,

  Thanks very much! I don't notice that.

Best,
Li