MadAnalysis 5

Forcing Tau leptons to undergo a BSM decay

Asked by HH

Dear experts,

I need to simulate a process in which the Tau lepton experiences a beyond the SM (BSM) decay. I tried generating the events, but I found out that in the .lhe file (before showering and detector simulation) the Tau lepton undergoes the desired BSM decay while in the final root file (showered with PYTHIA8 and analysed by DELPHES) that Tau lepton undergoes a SM decay. Looking at the PYTHIA8 log file, in the "hard process", Tau is decayed through the BSM mode, while in the "complete event", the same Tau is decayed through a SM decay mode.

It seems PYTHIA8 does NOT notice that Tau has already decayed in Mad level. And therefore performs showering as usual.

Would you please let me know how can I generate such a process?

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Solved by:
Jack Y. Araz
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Best Jack Y. Araz (jackaraz) said : 		#1

Hi

This I believe is a question for MadGraph and/or Pythia developers. MadAnalysis, as the name suggests, only a tool to do the analysis not to generate the events. We are independent of MadGraph and Pythia.

Cheers

—
Jack Y. Araz

> On Dec 5, 2020, at 1:05 PM, HH <email address hidden> wrote:
>
> New question #694361 on MadAnalysis 5:
> https://answers.launchpad.net/madanalysis5/+question/694361
>
> Dear experts,
>
> I need to simulate a process in which the Tau lepton experiences a beyond the SM (BSM) decay. I tried generating the events, but I found out that in the .lhe file (before showering and detector simulation) the Tau lepton undergoes the desired BSM decay while in the final root file (showered with PYTHIA8 and analysed by DELPHES) that Tau lepton undergoes a SM decay. Looking at the PYTHIA8 log file, in the "hard process", Tau is decayed through the BSM mode, while in the "complete event", the same Tau is decayed through a SM decay mode.
>
> It seems PYTHIA8 does NOT notice that Tau has already decayed in Mad level. And therefore performs showering as usual.
>
> Would you please let me know how can I generate such a process?
>
> --
> You received this question notification because you are an answer
> contact for MadAnalysis 5.

Revision history for this message
HH (hh-madgrapher) said : 		#2

Sorry I posted my question on the wrong page.

Revision history for this message
HH (hh-madgrapher) said : 		#3

Thanks Jack Y. Araz, that solved my question.