Madgraph giving lower than expected production cross section for BSM process

Asked by Basabendu on 2018-01-08

Dear Madgraph team,

In our model we are trying to produce two BSM charged fermions (on-shell) and looking for their subsequent decay into 3-body final state through off-shell W boson. The answer we are getting is 10^-10 times lesser than what we expect intuitively (from branching of the on-shell charged particles). The process we are generating is as follows:

p p > ~PSI+ ~psi- , (~psi- > l- vl~ ~psi1) , (~PSI+ > l+ vl ~PSI1)

where ~PSI+,~psi- are charged, while ~PSI1 is the neutral BSM particles. The production cross section of p p > ~PSI+ ~psi- is of the order of 1pb and the charged BSM particles have branching fractions of ~0.2 each. Then how madgraph is giving such small cross section when we take the production and the consequent decays together?

Thank you.

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FAQ #2442: “why production and decay cross-section didn't agree.”.

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