Possible to change sin^2(theta_w)?

Hi Josh,

Everything is possible but this is indeed not trivial.
My main worry is how you preserve gauge invariance if you want to change sin^2(theta_w) but not changing the mass.
(Note that if gauge invariance is broken, the lorentz invariance of our result is also in jeopardy).

Cheers,

Olivier

On Oct 1, 2014, at 7:31 PM, Josh Bendavid <email address hidden> wrote:

> New question #255263 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/255263
>
> Is it possible to change sin^2(theta_w) in generation? (In terms of the effect on the helicity struture of the Z-fermion-fermion coupling for example.)
>
> Looking at the model definition it seems not straightforward to do it without messing up the couplings and/or the W and Z mass.
> (This question comes from people interested in Z-polarization studies)
>
> Thanks,
> Josh
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Ok thanks.

I suppose if we want to vary that for some drell yan studies it's actually not a big deal to mess up the w mass a bit.

Is there any particular motivation to do this by varying 1/alphaem as opposed to Gf? (I suppose it is ~safe to vary either of these at the level of the restrict dat file?)

Hi,

> Is there any particular motivation to do this by varying 1/alphaem as
> opposed to Gf? (I suppose it is ~safe to vary either of these at the
> level of the restrict dat file?)

I do not see any.

Cheers,

Olivier

On Oct 1, 2014, at 11:21 PM, Josh Bendavid <email address hidden> wrote:

> Question #255263 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/255263
>
> Status: Answered => Open
>
> Josh Bendavid is still having a problem:
> Ok thanks.
>
> I suppose if we want to vary that for some drell yan studies it's
> actually not a big deal to mess up the w mass a bit.
>
> Is there any particular motivation to do this by varying 1/alphaem as
> opposed to Gf? (I suppose it is ~safe to vary either of these at the
> level of the restrict dat file?)
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Dear experts,

could somebody please explain how/where to find the sin^2(theta_w) value, that is used/configured in MadGraph?

Thanks,
Thomas

Hi,

after your "import model" command, you can do
"display paramaters"
There you will see all the parameters of the model and how they are defined.

Cheers,

Olivier

> On 27 Sep 2018, at 14:42, Thomas Müller <email address hidden> wrote:
>
> Question #255263 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/255263
>
> Thomas Müller requested more information:
> Dear experts,
>
> could somebody please explain how/where to find the sin^2(theta_w)
> value, that is used/configured in MadGraph?
>
> Thanks,
> Thomas
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.