8.1. Exotic physics¶
It is possible to add your own models to Sherpa in a straightforward way.
To illustrate, a simple example has been included in the directory
Examples/Models/SM_ZPrime, showing how to add a Z-prime boson to
the Standard Model.
The important features of this example include:
This file contains the initialisation of the Z-prime boson. The properties of the Z-prime are set here, such as mass, width, electromagnetic charge, spin etc.
This file contains the definition of the Z-prime boson’s interactions. The right- and left-handed couplings to each of the fermions are set here.
This shows how to compile the sources above into a shared library.
SHERPA_LDADD: SMZprimein the config file.
This line tells Sherpa to load the extra libraries created from the *.C files above.
MODEL: SMZprimein the config file.
This line tells Sherpa which model to use for the run.
The following lines in the config file:
PARTICLE_DATA: 32: Mass: 1000 Width: 50
These lines show how you can overrule the choices you made for the properties of the new particle in the
SM_Zprime.Cfile. For more information on changing parameters in Sherpa, see Input structure and Parameters.
Zp_cpl_R: 0.6set the couplings to left and right handed fermions in the config file.
To use this model, create the libraries for Sherpa to use by running
in this directory. Then run Sherpa as normal:
To implement your own model, copy these example files anywhere and modify them according to your needs.
Note: You don’t have to modify or recompile any part of Sherpa to use
your model. As long as the
SHERPA_LDADD parameter is specified as
above, Sherpa will pick up your model automatically.
Furthermore note: New physics models with an existing implementation in FeynRules, cf. [CD09] and [CdAD+11], can directly be invoked using Sherpa’s support for the UFO model format, see UFO Model Interface.