Author

Maksym Ovchynnikov (maksym.ovchynnikovATcern.ch).

Model description

The Chern-Simons portal extends the Standard Model by adding a new vector particle with zero electric charge, the X boson, interacting with the Standard Model electroweak gauge bosons, W, Z,

 $\!\gamma\!$ 

, via pseudo Chern-Simons current. After acquiring the Higgs VEV, the interaction of the X boson has the form [1][2]

 $\mathcal{L}_{X} = \mathcal{L}_{X,\text{kin}}+\epsilon^{\mu\nu\alpha\beta}\left(W_{\mu}X_{\nu}\partial_{\alpha}WY{\dagger}_{\beta}+\text{h.c.} + c_{Z}Z_{\mu}X_{\nu}\partial_{\alpha}Z_{\beta}+c_{Z\gamma}Z_{\mu}X_{\nu}\partial_{\alpha}A_{\beta}\right)$ 

$

 \!\dots \! 

$

 $\mathcal{O}_{R} = \!\left( \bar{t}_R \gamma^\mu t_R \right) \!\left( \bar{t}_R \gamma_\mu t_R \right)$ 

 $ \!\left( \bar{t}_R \gamma^\mu t_R \right) \!\left( \bar{t}_R \gamma_\mu t_R \right)$ 

 $\mathcal{O}_{X} = \!\left( \bar{t}_R \gamma^\mu t_R \right) \!\left( \bar{t}_R \gamma_\mu t_R \right)$ 

Implementation and usage description

The model has been implemented using merging of ​SM.fr and ​Chern-Simons-Portal.fr files. The implementation introduces one real new vector particle - X boson with the name xb. The implementation contains 6 new parameters: the coupling to W bosons cW (default value: 0.001), the coupling to Z bosons cZ (default value: 0.001), the coupling to the Z boson and photon cZgamma (default value: 0.001), the non-minimal axial-vector coupling to muons Cmu (default value: 0.1), the X boson mass Mxb (default value: 1 in units of GeV), the X boson width Wxb (default value: 1 in units of GeV). The implementation is performed in the unitary gauge. The implementation format is the UFO format.

To use the model, unpack the ​ChernSimons_UFO.zip archive and move the resulting folder ChernSimons_UFO to the directory /models of your ​MadGraph directory.

Files

• ​Chern-Simons-Portal.fr: this is the main file.
• ​ChernSimons.nb: this is an example Mathematica notebook that loads the model, calculates Feynman rules and makes the UFO implementation. Note that it requires the SM model file of the ​SM implementation of FeynRules.
• ​ChernSimons_UFO.zip: UFO format implementation for ​MadGraph.

References

Please cite [3] when using the model file.

• [1] I. Antoniadis, A. Boyarsky, S. Espahbodi, O. Ruchayskiy, J.D. Wells. Anomaly driven signatures of new invisible physics at the Large Hadron Collider. ​hep-ph/0901.0639

• [2] S. Alekhin et.al. A facility to Search for Hidden Particles at the CERN SPS: the SHiP physics case. ​hep-ph/1504.04855

• [3] K. Bondarenko, A. Boyarsky, M. Ovchynnikov, O. Ruchayskiy, L. Shchutska. Probing new physics with displaced vertices: muon tracker at CMS. ​hep-ph/1903.11918