Negative BR

Dear Anton,

negative Br is the indication of the loss of the gauge invariance.So the
problem is in your implementation of the model. In which gauge did you
implement it?Default gauge in CalcHEP is t'Hoof Feynman one. If you are
using it -- you need to make sure that you have impleented the model in
this gauge correctly

Regards,

Alexander

On 31/10/2018 21:42, Anton Kuncinas wrote:
> New question #675831 on CalcHEP:
> https://answers.launchpad.net/calchep/+question/675831
>
> Dear CalcHEP team,
>
> I came across the following problem: some of the branching ratios are negative when unitarity gauge is switched off. Model files are generated using SARAH. I took a look at several other posts but failed to track down the issue. I am currently in contact with F. Staub but it seems that the generated files are OK and moreover I checked most of the troublesome couplings involving Goldstone bosons and those agree with the ones derived earlier. I tried to play around with lgrng.mdl file by trying to "fix" the troublesome terms by introducing an additional "-" sign but this makes little sense to me. I realized the following thing: in our model couplings involving charged scalars are related by conjugation, e.g. g( h3 Hm2 WP.f ) = g( h3 Hp2 Wm.f )^\dagger. Is that a possible issue?
>
> With best regards,
> Anton
>
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Dear Alexander,

I should have stated that I took a look at the following post https://answers.launchpad.net/calchep/+question/675273, where you stated that: ¨Negative width in t'Hooft-Feynman gauge is the sign of absense of gauge invariance¨. That is why I consulted F. Staub in the first place. Also Feynman gauge is used.

With best regards,
Anton

Dear Anton,
so you need to check model implementation -- the results in both gauges
should coincide. Once
the model in t'Hooft Feynman gauge is implemented correctly, the results
from two gauges will coincide since CalcHEP
"knows" Feynman rules in  Unitary gauge from your t'Hooft Feynman gauge
implementation.
Regards,
Alexander

On Thu, 1 Nov 2018, 07:27 Anton Kuncinas,
<<email address hidden>
<mailto:<email address hidden>>> wrote:

    Question #675831 on CalcHEP changed:
    https://answers.launchpad.net/calchep/+question/675831

    Anton Kuncinas posted a new comment:
    Dear Alexander,

    I should have stated that I took a look at the following post
    https://answers.launchpad.net/calchep/+question/675273, where you stated
    that: ¨Negative width in t'Hooft-Feynman gauge is the sign of absense of
    gauge invariance¨. That is why I consulted F. Staub in the first place.
    Also Feynman gauge is used.

    With best regards,
    Anton

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