Issues with MSSM decays
Hi all,
I've been encountering some strange results when I calculate some processes using the built-in MSSM model in MadGraph, specifically those involving decays of neutralinos. I've tried using param_cards from different sources such as SPheno, SuSpect+SDECAY, etc. which all result in similar answers.
Bizarre results for cross-section times branching ratio of n1:
When I generate the process p p > n1 n1, n1 > ta+ ta1- and generate events, I find that it takes an extremely long time compared to similar processes, and ends up generating only 3-10 events and giving a cross-section several orders of magnitude too large-- much larger than the result for p p > n1 n1, which generates 1000 events in a minute and gives a sensible cross-section. The process p p > n2 n2, n2 > ta+ ta1- however is fast and gives a sensible answer (smaller than the p p > n2 n2 cross-section). I get a similar problem replacing the stau with a selectron/smuon if those decays are allowed.
Inconsistent results for decay widths to staus:
When I calculate the decay widths for the processes n1 > ta+ ta1- and n2 > ta+ ta1-, I find them to be significantly off (factor of a few) from the results in the param_card that I produced using various SUSY calculators (SPheno, SDECAY, etc.). The decay widths to e's or mu's are very similar between MadGraph and the calculators though.
Does anyone have some idea what could be happening here to give these results? I can post the banners if they would help.
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- Johan Alwall
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