My first study of SARAH modle with FeynArts

Questions concerning the interface to FeynArts/FormCalc
phy1002
Posts: 12
Joined: 6. Sep 2016, 13:27

My first study of SARAH modle with FeynArts

Postby phy1002 » 28. Sep 2016, 00:28

Hello sir,

In usual FeynArts needs two files for a new model .mod file which contain the classes definitions and couplings and .gen file
which contains the model generic propagators .. while MakeFeynArts[] for a model like B-L-SSM-IS gives only BLSSMISEWSB.mod , ParticleNamesFeynArts.dat and Substitutions-BLSSMISEWSB.m files . The default generic model for FeynArts if we didn't determine is Lorentz so will this be ok ?

Now in FeynArts I'm facing some problems .. I try to generate self energy diagram for a particle like S_2 (in SARAH/Models/ B-L-SSM-IS/particles.m it's defined by this line {FS2, { LaTeX -> "S_2"}}, )

so I write in FeynArts

topo1 = CreateTopologies[1, 1 -> 1, ExcludeTopologies -> {Internal}];

diag = InsertFields[topo1, {F[1, {7}]} -> {F[1, {7}]}, InsertionLevel -> {Classes}, Model -> "BLSSMISEWSB"];

I thought it will be the 7th or 8th neutrino, since the first 3 neutrinos are the Left-SM neutrinos, and I think the second three are the Right-neutrinos, but it gives me graphs like in the attached 11.png .. I don't know what are h_k and e^-_k , if h is higgs it has no index k and there is no vertices like these in the model ..

Also why the particles are not named by their Latex names as in particles.m file ? I tried for instance for electron neutrino

diag = InsertFields[topo1, {F[1, {1}]} -> {F[1, {1}]}, InsertionLevel -> {Classes}, Model -> "BLSSMISEWSB"];

but it gives the same of 11.png but with neutrino index 1 instead of 7, while in SM it gives a figure as in the attached 22.png , i.e., e- index for electron neutrino and etc.

Do I miss some thing for the implementation of the model from SARAH to FeynArts ?

Thank you .
Attachments
22.png
22.png (6.07 KiB) Viewed 174 times
11.png
11.png (18.95 KiB) Viewed 174 times

FStaub
Site Admin
Posts: 689
Joined: 13. Apr 2016, 14:05

Re: My first study of SARAH modle with FeynArts

Postby FStaub » 28. Sep 2016, 08:35

Hi,

I have to say that it seems to me that your questions are not necessarily of technical nature (i.e. related to SARAH, FeynArts), but more about the basic physics. This is not necessarily the purpose of the forum here. Nevertheless, just a few comments:

I thought it will be the 7th or 8th neutrino, since the first 3 neutrinos are the Left-SM neutrinos, and I think the second three are the Right-neutrinos, but it gives me graphs like in the attached 11.png .. I don't know what are h_k and e^-_k , if h is higgs it has no index k and there is no vertices like these in the model ..

In general, all neutrinos do mix, and what nature a given generation of state has depends on the parameter point. Therefore, such a classification as you do is not possible in general. You should look deeper into the topics "gauge eigenstates" vs. "mass eigenstates". Maybe, this model is not a good starting point, and you should read about this in a simpler one like the MSSM and study their the neutralino sector.

Why should the Higgs doesn't carry any generation index? There are lots of Higgs states in the model and all of them do mix in general as the neutrinos do. Therefore, my same comment applies.

but it gives the same of 11.png but with neutrino index 1 instead of 7, while in SM it gives a figure as in the attached 22.png , i.e., e- index for electron neutrino and etc.

All of that is just nomenclature. Auto-generated files by SARAH do use a bit other syntax and names as the standard FeynArts model files do. The main differences is FA uses S[X] with different X to label the different real scalars while SARAH groups them into S[A,{B}] where A is different for CP-evne and odd states, and B counts the generations.

Again, please use this forum for technical related questions. The physics questions are better discussed with your supervisor.


Cheers,
Florian


Return to “FeynArts/FormCalc”

Who is online

Users browsing this forum: No registered users and 0 guests