cross-section difference with different calculation methods
Dear all,
First of all, I already had a look at [1] but it did not solve the problem yet.
[1] https:/
I use MG to calculate cross-sections for a SUSY model imported in the UFO format. Decay widths and masses are calculated with Spheno and used in the param card.
I calculated cross sections in two ways:
1)
define smuL = se2 se2c
define mu = e2 e2bar
define fgq = u1 u1bar d1 d1bar
generate p p > smuL, (smuL > mu n1, (n1 > fgq fgq mu)) @0
2)
define smuL = se2 se2c
define mu = e2 e2bar
define fgq = u1 u1bar d1 d1bar
generate p p > mu n1 @0
The resulting cross-sections from method 1 is up to 30% larger than the one from method 2 * BR from the model (depending on the parameter point). If I use 'generate p p > smuL, (smuL > mu n1)' , I get consistent results to method 2, so I guess that the three body decay of the n1 is the culprit here.
Concerning the suggested solutions in [1]:
- cut_decays is False in both cases
- the bwcutoff parameter is set to 150000, so I assume that the processes should be identical
- the width of the n1 can be rather small (reaching 10^-10 at masses of ~10^3) but this should be still far enough away from the limit mentioned in [1]. I tested running with a much larger width for version 1 and got the same result (module ratio of the width)
Do you know what could be reason for this difference? Are these differences expected? Is maybe one of the method giving more accurate results?
If you need more input (param_cards, models, etc) please let me know. I'm using Madgraph 2.3.3.
Thanks a lot,
Philipp
Question information
- Language:
- English Edit question
- Status:
- Answered
- Assignee:
- No assignee Edit question
- Last query:
- Last reply:
Can you help with this problem?
Provide an answer of your own, or ask Philipp Millet for more information if necessary.