MadGraph5_aMC@NLO

regarding generating new physics contributions at NLO level in madgraph

Asked by Disha Bhatia

Hi,

I am trying to compute the full BSM contribution to t t~ at one loop in QCD.

I am proceeding this through the command : p p > t t~ [QCD] NEW=99 QCD=99,
however this is giving me still the contributions due to QCD, I also tried other variants, for ex NEW=2 etc
but none is working. It gives me only QCD contribution:

generate p p > t t~ / z a [QCD] NEW=2
Interpreting 'NEW=2' as 'NEW<=2'
INFO: Generating FKS-subtracted matrix elements for born process: g g > t t~ NEW<=2 [ all = QCD ] / z a (1 / 9)
INFO: Generating FKS-subtracted matrix elements for born process: u u~ > t t~ NEW<=2 [ all = QCD ] / z a (2 / 9)
INFO: Generating FKS-subtracted matrix elements for born process: c c~ > t t~ NEW<=2 [ all = QCD ] / z a (3 / 9)
INFO: Generating FKS-subtracted matrix elements for born process: d d~ > t t~ NEW<=2 [ all = QCD ] / z a (4 / 9)
INFO: Generating FKS-subtracted matrix elements for born process: s s~ > t t~ NEW<=2 [ all = QCD ] / z a (5 / 9)
INFO: Generating FKS-subtracted matrix elements for born process: u~ u > t t~ NEW<=2 [ all = QCD ] / z a (6 / 9)
INFO: Generating FKS-subtracted matrix elements for born process: c~ c > t t~ NEW<=2 [ all = QCD ] / z a (7 / 9)
INFO: Generating FKS-subtracted matrix elements for born process: d~ d > t t~ NEW<=2 [ all = QCD ] / z a (8 / 9)
INFO: Generating FKS-subtracted matrix elements for born process: s~ s > t t~ NEW<=2 [ all = QCD ] / z a (9 / 9)
INFO: Generating virtual matrix elements using MadLoop:
INFO: Generating virtual matrix element with MadLoop for process: g g > t t~ NEW=0 QCD<=2 [ all = QCD ] / z a (1 / 9)
INFO: Generating virtual matrix elements using MadLoop:
INFO: Generating virtual matrix element with MadLoop for process: u u~ > t t~ NEW=0 QCD<=2 [ all = QCD ] / z a (2 / 9)
INFO: Generating virtual matrix elements using MadLoop:
INFO: Generating virtual matrix element with MadLoop for process: c c~ > t t~ NEW=0 QCD<=2 [ all = QCD ] / z a (3 / 9)
INFO: Generating virtual matrix elements using MadLoop:
INFO: Generating virtual matrix element with MadLoop for process: d d~ > t t~ NEW=0 QCD<=2 [ all = QCD ] / z a (4 / 9)
INFO: Generating virtual matrix elements using MadLoop:
INFO: Generating virtual matrix element with MadLoop for process: s s~ > t t~ NEW=0 QCD<=2 [ all = QCD ] / z a (5 / 9)
INFO: Generating virtual matrix elements using MadLoop:
INFO: Generating virtual matrix element with MadLoop for process: u~ u > t t~ NEW=0 QCD<=2 [ all = QCD ] / z a (6 / 9)
INFO: Generating virtual matrix elements using MadLoop:
INFO: Generating virtual matrix element with MadLoop for process: c~ c > t t~ NEW=0 QCD<=2 [ all = QCD ] / z a (7 / 9)
INFO: Generating virtual matrix elements using MadLoop:
INFO: Generating virtual matrix element with MadLoop for process: d~ d > t t~ NEW=0 QCD<=2 [ all = QCD ] / z a (8 / 9)
INFO: Generating virtual matrix elements using MadLoop:
INFO: Generating virtual matrix element with MadLoop for process: s~ s > t t~ NEW=0 QCD<=2 [ all = QCD ] / z a (9 / 9)
INFO: Generated 9 subprocesses with 136 real emission diagrams, 11 born diagrams and 124 virtual diagrams

AT LO, I tried to omit and add QED contributions which happen very nicely either by using QED=2/99

But my new physics contribution exists at one loop, and I am unable to generate the events together, this is crucial for me since I need the interference terms. Can you please help me in this regard?

Thanks,
Disha

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Without the model, I do not see how any of us will be able to comment on the issue.
Could you also specify which version of the code you are using.
And finally if you can provide the Feynman diagram of the loop that you want to be included in the computation.

With that information, I will be able to take a first look and then decide who in the teams will be able to help you.

Cheers,

Olivier

PS: If you want to attach file, you can either provide a link or convert this question to a bug report since questions does not handle file attachment.

> On 10 Aug 2021, at 21:15, Disha Bhatia <email address hidden> wrote:
>
> INFO: Generating FKS-subtracted matrix elements for born process: s~ s > t t~ NEW<=2 [ all = QCD ] / z a (9 / 9)

Revision history for this message
Disha Bhatia (dishabhatia1989) said : 		#2

Thanks Oliver, as per your suggestion I marked this question to the bug https://bugs.launchpad.net/mg5amcnlo/+bug/1939495.
I have also attached the model file and the diagram which I intend to add.

Can you help with this problem?

Provide an answer of your own, or ask Disha Bhatia for more information if necessary.

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