UFO with Majorana fermions

Asked by daniel jeans on 2020-07-07


I'm using v2.8.3, which I understood has support for Majorana fermions, trying to generate a process i a model with some heavy majorana neutrinos.
I'm using the UFO at https://feynrules.irmp.ucl.ac.be/raw-attachment/wiki/HeavyN/SM_HeavyN_CKM_AllMasses_LO.tgz
(linked from the page https://feynrules.irmp.ucl.ac.be/wiki/HeavyN )

So far I have no success; details below. I guess some rookie mistake...
any help/hints much appreciated.

Cheers, Daniel.

sindarin file :

?vis_history = false
model = SM_HeavyN_CKM_AllMasses_LO (ufo)
process testHN = "e-" , "e+" => "mu-" , "mu+"
beams = "e-" , "e+"
sqrts = 250 GeV
beams_pol_density = @(-1), @(+1)
beams_pol_fraction = 100%, 100%
n_events = 50
sample_format = lcio
integrate (testHN) {
iterations = 10:500:"gw",10:500:"g",10:500:"w",10:500:"gw"
simulate (testHN)

| Model: Generating model 'SM_HeavyN_CKM_AllMasses_LO' from UFO sources
| Model: Searching for UFO sources in working directory
| Model: Found UFO sources for model 'SM_HeavyN_CKM_AllMasses_LO'
O'Mega: found Majorana fermions!
O'Mega: falling back to the Majorana representation for all fermions.
| Model: Model file 'SM_HeavyN_CKM_AllMasses_LO.ufo.mdl' generated
| Reading model file 'SM_HeavyN_CKM_AllMasses_LO.ufo.mdl'
?vis_history = false
| Switching to model 'SM_HeavyN_CKM_AllMasses_LO' (generated from UFO source)
[1/1] e- e+ -> mu- mu+ ...O'Mega: found Majorana fermions: use a supporting binary!
SUMMARY: 0 vertices
Warning: Process 'testHN': matrix element vanishes

Question information

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Juergen Reuter Edit question
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daniel jeans
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Juergen Reuter (j.r.reuter) said : #1

Indeed, that is something that we haven't tested before the release made a bit under pressure. We will fix this in a backported release bugfix (called v2.8.4), hopefully until the end of the week. The changes only affect UFO Majorana models.

daniel jeans (danieljeans) said : #2

Thanks Juergen! I'll try again with the next release when it comes out.

Juergen Reuter (j.r.reuter) said : #3

Indeed, it's out: 2.8.4. The only difference compared to 2.8.3 is this bug fix for Majorana fermion UFO models. Thanks for reporting this. We received a second report from the Dresden/Warsaw group looking into extended SUSY models shifted later almost exactly by the time zone difference^^
Please check it out, and if it works mark this as solved, please.

daniel jeans (danieljeans) said : #4

thanks, 284 gives me non-zero results.