SM + new DY resonances

We consider new spin-0, 1, and 2 resonances that can contribute to the s-channel Drell-Yan processes p,p->l+,l-,X and p,p->l,v,X where l is a charged lepton, v is a neutrino or antineutrino and X is the inclusive hadronic remnants. We implement the most general Lagrangian between these new bosons and the SM fermions and gluons allowed by Lorentz, quantum chromodynamic and electromagnetic invariance. In each case, we only include the leading effective terms which are either dimension-4 or dimension-5 operators. Furthermore, we drop all terms which vanish when the masses of the initial-state and final-state particles are taken to zero. Further details can be found in the reference below.

Implementation Author

• Neil Christensen
  • University of Wisconsin - Madison
  • neil@…

in collaboration with Cheng-Wei Chiang, Gui-Jun Ding, and Tao Han.

References

• ​arXiv:1107.5830

Model Files

• DY-SM-FR.tgz: FeynRules Model Files

Model Implementation

Details about this implementation can be found in the reference above. Additionally, the FeynRules automatic output for this model can be found here:

• DY-SM.pdf: Fields, parameters, Lagrangians and Vertices.

Instructions

We provide a basic notebook giving examples of how to run the FeynRules interfaces on this model. Before running the notebook, the user must change $FeynRulesPath to the path of FeynRules on their computer and the user must change $ModelDir to the path to the DY-SM FeynRules model files downloaded from here:

• SMplus.nb.gz

After loading the model in CalcHEP or MadGraph, suppose you want to run a Z' with SM like couplings. The Z' name is VV, the mass is MVV, the width is WVV and you would set the couplings as:

• gVuR11=0.03465*(1-8/3*0.23369)
• gAuR11=0.03465*(-1)
• gVuR22=0.03465*(1-8/3*0.23369)
• gAuR22=0.03465*(-1)
• gVdR11=0.03465*(-1+4/3*0.23369)
• gAdR11=0.03465*(1)
• gVdR22=0.03465*(-1+4/3*0.23369)
• gAdR22=0.03465*(1)
• gVlR11=-1+4*0.23369
• gAlR11=1
• gVlR22=-1+4*0.23369
• gAlR22=1

Interfaces

This model implementation is known to work with ​CalcHEP. The CalcHEP files can be found here:

• SM-DY-CH.tgz

This model also runs with ​MadGraph 5 but has not been as thoroughly tested. The files can be found here:

• dy_sm_fr.tgz

Please report any bugs to Neil Christensen.

Validation

The Feynman rules were computed by hand and compared with the FeynRules vertices and found to agree. Furthermore, the squared amplitudes for several Drell-Yan processes were calculated by hand and compared with the analytic output of CalcHEP and found to agree. Hermiticity of the Lagrangian was also tested at the Feynman rules level.