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SARAH

Low_or_High_scale_SPheno_version

Last edited by Martin Gabelmann
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Low or High scale SPheno version

High-scale SPheno version

In a GUT version of SPhenoa RGE running between the electroweak, SUSY and GUT scale is supported. The user can define appropriate boundary conditions at each of these three scales. Furthermore, also threshold effects by including additional scales where heavy particles are integrated out can optionally be included. Finally, the user can define a condition which has to be satisfied to identify the GUT scale. The most common choice is the unification scale of gauge couplings, but also other choices like Yukawa unification are possible. In addition, these version include also the possible to define the entire input at the SUSY scale and skip the RGE running to the GUT scale.

In that case, the following

Boundary conditions in SPheno can be defined
  • BoundaryLowScaleInput
  • BoundaryEWSBScale
  • BoundarySUSYScale
  • BoundaryHighScale
  • BoundaryEWSBScaleRunningDown

Also, other information must be present as:

GUT scale condition in SPheno The renormalisation scale in SPheno

Several boundary conditions

In a high-scale version it is possible to define several boundary conditions in a single SPheno.m file. In that case, the above lists of boundary conditions become nested lists. One can choose then in the numerical session in SPheno which set of boundary conditions shall be used via the block MODSEL

Block MODSEL      #
1 1               #  1/0: High/low scale input
2 N               # Boundary Condition
...

Here, N is an integer from 1 up to the number of defined boundary conditions. See also the options to define several sets of boundary conditions and using several sets of input parameters.

Low scale SPheno version

It is also possible to create a SPheno version with much less features which only accepts low energy input. That means, the RGEs are not written out and also the fit to the electroweak data is not performed in the numerical evaluation of one point. It just solves the tadpole equations, calculates the tree- and one-loop masses as well as the decay widths and branching ratios. The advantage of such a SPheno version is that it works with a larger set of models, e.g. also non-SUSY models or other models not supported by a full evaluation as explained in here. To get a SPheno version without RGE evolution, insert

OnlyLowEnergySPheno = True;

in SPheno.m. The remaining information needed by SARAH is only a small subset of the settings and only the following set of boundary conditions is needed

  • BoundaryLowScaleInput

Note that the Automatic statement for defining the list of particles for which the decays shall be calculated does not work in this case as SARAH doesn’t differ between SUSY or Non-SUSY particle in order to make the output as generic as possible. Therefore, the explicit lists of the decaying particles must be given.

See also