gg -> ta+ ta- j

Asked by shaodingyu on 2018-02-20

Dear MG5 authors,

I am trying to generate process gg>ta+ta-j, where I want to include both off-shell processes z*(a*)>ta+ta- and h*>ta+ta-.

The document pro_card.dat is written as

*************************************************

import model loop_sm
# Define multiparticle labels
define p = g
define j = g u c d s u~ c~ d~ s~
define l+ = e+ mu+
define l- = e- mu-
define vl = ve vm vt
define vl~ = ve~ vm~ vt~
# Specify process(es) to run
generate p p > ta+ ta- j [QCD]
# Output processes to MadEvent directory
 output ggllj

*************************************************

However, the output results don't include h*>ta+ta- channel. If I specify the intermedia states as

*************************************************

generate p p > z g > ta+ ta- g [QCD]
add process p p > h g > ta+ ta- g [QCD]

*************************************************

Then I can generate two processes. But the output result looks like it doesn't include interference effects. Do you know how to generate interference for this channel correctly?

Best,
Dingyu

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Last query:
2018-02-20
Last reply:
2018-02-20

Hi,

The first think that I need to be sure is which contribution do you want to include in your computation.
Here my understanding is that you are only interested in the loop-induced contribution (the Z diagram can also be generated via quark pair at tree level and I will here remove that contribution).

Removing correctly all the loop related to the tree-level Z diagram is not something trivial that you can do out of the box and you need to hack madgraph in the following way:

=== modified file 'madgraph/loop/loop_diagram_generation.py'
--- madgraph/loop/loop_diagram_generation.py 2017-07-31 12:50:36 +0000
+++ madgraph/loop/loop_diagram_generation.py 2018-02-20 16:49:23 +0000
@@ -384,7 +384,7 @@
         # By default the user filter does nothing if filter is not set,
         # if you want to turn it on and edit it by hand, then set the
         # variable edit_filter_manually to True
- edit_filter_manually = False
+ edit_filter_manually = True
         if not edit_filter_manually and filter in [None,'None']:
             return
         if isinstance(filter,str) and filter.lower() == 'true':
@@ -418,8 +418,8 @@
 # if any([abs(pdg) not in range(1,7) for pdg in diag.get_loop_lines_pdgs()]):
 # valid_diag = False

-# if any([abs(i)!=1000021 for i in diag.get_loop_lines_pdgs()]):
-# valid_diag=False
+ if any([abs(i)==21 for i in diag.get_loop_lines_pdgs()]):
+ valid_diag=False
 # if len(diag.get_loop_lines_pdgs())<4:
 # valid_diag = False

after that change you can do:

generate p p > Z | h > ta+ ta- j [noborn=QCD]

Cheers,

Olivier

> On 20 Feb 2018, at 09:42, shaodingyu <email address hidden> wrote:
>
> New question #664668 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/664668
>
> Dear MG5 authors,
>
> I am trying to generate process gg>ta+ta-j, where I want to include both off-shell processes z*(a*)>ta+ta- and h*>ta+ta-.
>
> The document pro_card.dat is written as
>
> *************************************************
>
> import model loop_sm
> # Define multiparticle labels
> define p = g
> define j = g u c d s u~ c~ d~ s~
> define l+ = e+ mu+
> define l- = e- mu-
> define vl = ve vm vt
> define vl~ = ve~ vm~ vt~
> # Specify process(es) to run
> generate p p > ta+ ta- j [QCD]
> # Output processes to MadEvent directory
> output ggllj
>
> *************************************************
>
> However, the output results don't include h*>ta+ta- channel. If I specify the intermedia states as
>
>
> *************************************************
>
> generate p p > z g > ta+ ta- g [QCD]
> add process p p > h g > ta+ ta- g [QCD]
>
>
> *************************************************
>
> Then I can generate two processes. But the output result looks like it doesn't include interference effects. Do you know how to generate interference for this channel correctly?
>
> Best,
> Dingyu
>
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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