Simplified SUSY models with different mixing cases

[Alkass]

Hi

Probably a bit technical, but here it is.

I am trying to construct some simplfied SUSY models (that is, you only tune the masses of the core process, while all the rest are decoupled), and I would like to play with different mixing scenarios for the neutralino and charginos, so to get a more bino-like or wino-like scenario.

Now, the mixing is basically depicted in the .slha one can use in the UMIX,VMIX and NMIX blocks, but given that the actul structure of the matrix is not trivial to calculate by hand (in contrast for example if you want to get the mixing for top-squark, where you only need the theta_mixing and you can easily get the block for the .slha), I was wondering if someone has a hint how to get blocks for max, min and no_mixing between chargino and neutralinos, so to then generate events with Pythia

Thanks in advance

Alex

 

[AndyW]

Hi Alex,

Thank you for your question. The mixing between charginos and neutralinos is an important aspect of SUSY models and can greatly affect the predicted particle masses and interactions. As you mentioned, the mixing is determined by the UMIX, VMIX, and NMIX blocks in the .slha file.

To generate events with different mixing scenarios, you can use the SUSY event generator Pythia. Pythia has an option to read in a .slha file and generate events based on the particle content and mixing parameters specified in the file. However, if you want to manually calculate the mixing for different scenarios, you can use the formulas and algorithms provided in the literature.

To calculate the mixing for charginos and neutralinos, you will need to use the mass matrices for these particles. These can be found in the literature or generated using a SUSY model calculator such as SPheno. Once you have the mass matrices, you can use the diagonalization process to obtain the mixing angles and eigenstates.

For example, to get the maximum mixing scenario, you can set all the off-diagonal elements in the mass matrix to zero, resulting in a diagonal matrix. This will give you the maximum mixing between the particles. Similarly, for the minimum mixing scenario, you can set the off-diagonal elements to be equal to the diagonal elements, resulting in a diagonal matrix with equal elements.

I hope this helps. If you have any further questions or need clarification, please don't hesitate to ask.