Dear Florian

Previously we embedded a U(1)_R lepton number model with a right
handed neutrino superfield and studied the top squark phenomenology
of the model. We only looked at the leptonic decay modes of the
top quark.

We also found some interesting signals regarding the electroweak
sector. But I am facing an issue here ...

1. Neutralino and chargino pair production cross section through
Madgraph is giving me the correct result, however, the chargino-
neutralino associated production cross section is very low. I tried to
trace the problem and found that pp > W in Madgraph for our model
is giving a wrong value (10^-4 pb where the correct cross section
would be 10^+4 pb, Z boson production cross section is coming out
to be correct.)

I checked the couplings in the mathematica file and compared with the
MSSM file (Vertex[{VWm, Fu, bar[Fd]}]). They are same and the relevant
mass matrices i.e, ZUL and ZDL have similar entries.

Since the sneutrino in our scenario gets a vev and down type Higgs
field is integrated out. Therefore, apart from making this change
in SARAH, I had to correct a few errors coming from SPheno itself.
However, the W couplings to quarks should not get affected by that.
Could you please tell me where should I look for in order to find
the error.

best regards

Sabya

Hi,

did you check if the decays W -> q q' come out correctly? It might also be helpful to take a look at the log files runX_app.log hidden in SubProcesses/P0_xxxxx/GX/ to see the numerical values for all parameters and vertices MG is using.

Cheers,
Florian

Dear Florian

Thanks for your reply. It seems to me that in the SPheno SLHA file it clearly
writes the W mass as `24 --- 8.0349E+01 #VWM'. However, in the runx_app.log file
in Madgraph the Z mass and the corresponding width is printed correctly but only the W
boson width is printed in the External Params column. However, in the section
--internal params evaluated point by point it is indeed printing the W mass.

Is there any way to rectify this at the SPheno level?

With best regards

Sabya

Hi Sabya,

in general, the W mass is not an external parameter but calculated internally via (see parameters.py)
if you haven't changed that in your SARAH model (via DependenceNum). Thus, the value coming from SPheno is indeed not used for this case. So, if the calculated looks fine (there might be a difference of 1-2 GeV compared to the on-shell value, this shouldn't be an issue).

Cheers,
Florian

Dear Florian

Thanks for your mail. Indeed I checked the parameters.py file yesterday. The point was
since I have no H_d and hence no v_d (I had only v_L which acts as v_d). After making
this definition in SARAH I had to make some changes in SPheno also, as it still had some
v_d dependence. The same thing was happening with Madgraph. I changed the notation
in parameters.py file and its working fine now.

Thanks for your help again.

Best regards

Sabya