MadGraph5_aMC@NLO

different double poles between complex-mass and on-shell

Asked by Liang Dong

Hi,

I want to compute the process of " d d~ > b~ t W- [virt=QCD]" . Before "generate", I try to use two different schemes by typing "set complex_mass_scheme true" or not. The width of top quark is set to non-zero, and others zero. I can't understand why the two schemes result in different double poles.

Greetings,
Dong.

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
Hua-Sheng Shao Edit question
Solved by:
Hua-Sheng Shao
Solved:
Last query:
Last reply:
Revision history for this message
Best Hua-Sheng Shao (erdissshaw) said : 		#1

Hi,

You can not keep the width of external particles to be nonzero, which violates the unitarity.

Cheers,

Hua-Sheng

Revision history for this message
Liang Dong (leondong123) said : 		#2

Thanks Hua-Sheng Shao, that solved my question.