tomeichlersmith
commented
1 year ago This naive attempt does not function since $\epsilon$ has a strict, non-divergence limit of $\epsilon < 1$ leading to the following "zero cross section" error produced.
Survey return zero cross section.
Typical reasons are the following:
1) A massive s-channel particle has a width set to zero.
2) The pdf are zero for at least one of the initial state particles
or you are using maxjetflavor=4 for initial state b:s.
3) The cuts are too strong.
Please check/correct your param_card and/or your run_card.
Zero result detected: See https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FAQ-General-14
ln: failed to create symbolic link 'ME5_debug': File exists
quit
INFO: Following $\epsilon$ through our model leads to a lot of other parameters that are not included in the SIMP model (where I assume $\epsilon=1$ since $\epsilon$ is included in the production rate calculation). Below is the variable "cascade" in the parameters of the model, there are also references to some of these parameters in couplings (mostly eta).
since epsilon also affects the decay length of chi2, we delay including it in the chain until we are studying the vertex displacement affects downstream in the analysis pipeline. Having $\epsilon=1$ in the model makes it easier to include it later since we don't have to remember what its value was before.