CKM induced loop decays

[WojciechKotlarski]

Hi Florian,

Is it possible to get from SPheno loop-induces decays that go through a CKM matrix? Somethink like t -> c h? If so, can you point me to an example as it seems that none of CKM subfolders in Models directory contain a SPheno steering file.

Regards,
Wojciech

[FStaub]

Hi,

yes, for SM/CKM no SPheno output is possible because two field rotations are performed. However, that's just a choice of the basis and you should get the results also with the standard SM. There are two possibilities:
1) The results should show up in the general one-loop decay once the limit on the printed BR is reduced
2) You can add them via the FlavorKit interface similar to the example in 6.3.2 of 1503.04200 which shows how to add t->c\gamma

EDIT:
Sorry, the point (1) is wrong, because SPheno calculates by Tree x (Tree+Loop) which still vanishes. There is the hidden option to set in Settings.f90 the variable

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SquareFullAmplitudeDecays = True

instead of False which will calciulate (Tree x Loop)^2. However, that will be dangerous because that won't give a cancellation of divergences for decays which exist already at tree-level. Therefore, you might want to check the file Wrapper_LoopDecay_Fu_MODEL.f90 and search for

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 "------------------ Fu->Fu hh -----------------------"

and make the edit only for the specific channel you want to check.

Cheers,
Florian

[WojciechKotlarski]

Hi,

As always, thanks a lot for help. That solved my problem.

cheers,
Wojciech