MadGraph5_aMC@NLO

problem with taudecay_UFO

Asked by Gang Li on 2016-03-27

Hi,

I have problem with generating p p > ta+ ta-, ta+ > e+ ve vt~, ta- > e- ve~ vt with MG5_aMC_v2_3_3.
After I import model sm-lepton_masses and add model taudecay_UFO,
the cross section is 1209 +- 3.3 pb
which is larger than the cross section of p p > ta+ ta-, which is 836.4 +- 2.05 pb

I have checked the tau decay width in param, which is 2.270000e-12 (the sm value).
Besides, I have tried to increase the width to 2.270000e-5, in this way the cross section of
p p > ta+ ta-, ta+ > e+ ve vt~, ta- > e- ve~ vt is only 1.208e-11 +- 4.207e-14 pb.

I have also tried to import model sm-full. It does not work either.

Could you please help me?

Thanks in advance.
Gang Li

Question information

Language:
English Edit question
Status:
Open
For:
MadGraph5_aMC@NLO Edit question
Assignee:
Kentarou Mawatari Edit question
Last query:
2016-03-29
Last reply:
Kentarou Mawatari (kentarou-mawatari) said : #1

Hi Gang and Olivier,

I reproduced the problem, which is nothing related with TauDecay as the sm model can handle the leptonic decay.
Olivier, does the problem come from the too small tau width?

Kentarou

Gang Li (ligangpku) said : #2

Hi Kentarou,

Thanks for your reply.
Since I also want to generate the taus with hadronic decays, so I add the model taudecay_UFO.
(1) I have tried to generated p p > ta+ ta-, ta+ > e+ ve vt~, ta- > e- ve~ vt with only sm-full or sm-lepton_masses, the cross section is about 1209 pb.
(2) I have tried to generate p p > ta+ ta-, ta+ > pi+ vt~, ta- > pi- vt, using sm-lepton_masses and taudecay_UFO, the cross section is 434.7 +- 0.9713 pb.

Best,
Gang Li

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