# Internal BSM Models¶

A large number of BSM models are included in the Herwig release.

• A number of supersymmetric models are implemented.
• The Minimal Supersymmetric Standard Model (MSSM) is the minimal supersymmetric extension of the Standard Model. The parameters for the model are set in MSSM.model, an example of running the model for the LHC is provided in LHC-MSSM.in and for a future linear collider in ILC-MSSM.in. This model provides the basis for the implementation of all the other supersymmetric models which inherit from it.
• The Next-to-Minimal Supersymmetric Standard Model (NMSSM) includes an additional Higgs singlet field. The implementation inherits from that for the MSSM. The parameters for the model are set in and NMSSM.model and an example of running the model for the LHC is provided in LHC-NMSSM.in.
• The R-parity violating extension to the MSSM is implemented. Currently either bi-linear R-parity violating couplings, with parameters set in RPV-Bi.model, or tri-linear R-parity violating couplings, with parameters set in RPV-Tri.model, are allowed but not both simultaneously. An example of running either model for the LHC is provided in LHC-RPV.in.
The parameters for all these models can be read from SUSY Les Houches Accord (SLHA) files via the setup command.
• Four extra-dimensional models are implemented.
• In the Large-Extra dimensions model of Arkani-Hamed, Dimopoulos, and Dvali (ADD) only the gravitational force extents into the extra dimension which leads to the production of towers of graviton states as either missing transverse energy or changes to Standard Model processes due to the exchange of graviton towers. The parameters for the model are set in the ADD.model file and an example of running the model for the LHC is provided in LHC-ADD.in.
• As with the ADD model in the Randell-Sundrum model only gravity propagates in the extra dimension, however due the warped extra dimension in this case graviton resonances are produced. The parameters for the model are set in RS.model, an example of running the model for the LHC is provided in LHC-RS.in and for a future linear collider in ILC-RS.in.
• In the Minimal Universal Extra-Dimensions (MUED) model all the field propagate in the extra dimension leading to towers of Kaluza-Klein states. The parameters for the model are set in MUED.model, an example of running the model for the LHC is provided in LHC-MUED.in and for a future linear collider in ILC-MUED.in.
• A model for transplankian scattering which only requireas a new MatrixElement for the scattering process. An example of running the model for the LHC is provided in LHC-TRP.in.
• Two Little-Higgs models based on the idea that the Higgs boson is a pseudo-Goldstone boson arising from some global symmetry breaking at a TeV energy scale are implemented.
• The standard Little-Higgs model with an extra top quark is implemented with the additional parameters for the model set in LH.model and an example of running the model for the LHC is provided in LHC-LH.in.
• The Little-Higgs Models with T-parity conservation leading to additional parameters for all the Standard Model particles. The parameters for the model are set in LHTP.model and an example of running the model for the LHC is provided in LHC-LHTP.in.
• A model for Leptoquarks. The parameters for the model are set in Leptoquark.model and an example of running the model for the LHC is provided in LHC-LQ.in.
• A model for the production of either scalar or vector diquarks in the Sextet representation of QCD. The parameters for the model are set in Sextet.model and an example of running the model for the LHC is provided in LHC-Sextet.in.
• A model designed to try and explain the top forward-backward asymmetry observed by CDF. The parameters for the model are set in TTBA.model, an example of running the model for the LHC is provided in LHC-TTBA.in and for the Tevatron in TVT-TTBA.in.
• A model including a $$Z'$$ boson. The parameters for the model are set in Zprime.model and an example of running the model for the LHC is provided in LHC-ZP.in.

## Implementing New Models¶

While we would now strongly recommend that any new models are added using the UFO interface it is possible to implement them directly in Herwig. Two examples are given below.