Version 117 (modified by mashry, 4 years ago) (diff)


Alternative Left-Right Symmetric Model


Mustafa Ashry

  1. Center for Fundamental Physics, Zewail City of Science and Technology, Sheikh Zayed, 12588 Giza, Egypt
  2. Department of Mathematics, Faculty of Science, Cairo University, 12613 Giza, Egypt



Model Description

As any other left-right symmetric model, ALRM is a QFT gauged by the gauge symmetry group SU(3)_C×SU(2)_L×SU(2)_R×U(1)_B-L. The latter B and L being the baryon and lepton numbers. An extra discrete symmetry S is imposed to distinguish between Higgs fields and their dual fields and hence their interactions.

As in the SM, left fermions compose SU(2)_L doublets. Right charged leptons are accommodated in SU(2)_R doublets with corresponding extra particles (scotinos) and right up-quarks in SU(2)_R doublets with corresponding extra down-type exotic quarks. Right neutrinos and down-quarks are SU(2)_L,R singlets. The Higgs sector composes of an SU(2)_L-doublet, an SU(2)_R-doublet and a bidoublet.

The electroweak left-right symmetry SU(2)_L×SU(2)_R×U(1)_B-L is broken down to the SM electroweak symmetry SU(2)_L×U(1)_Y, Y being the hypercharge, by the SU(2)_R-doublet vev, then the electroweak symmetry is broken down to the U(1)_em through the bidoublet and the SU(2)_L-doublet vevs. Accordingly, all ferminos and gauge bosons (except of course photon) become massive via Higgs mechanism. The physical gauge sector of the model contains the electroweak gauge bosons (photon, W and Z bosons) in addition to two extra gauge bosons (W' and Z' ) correspond to the SU(2)_R group.

Dirac (massive) neutrinos are considered with the mixing MNS matrix implemented in the normal hierarchy. The case of Majorana neutrinos is considered in many other models' files and can be brought to be implemented here easily. Three mixed generations of quarks are considered and hence the general case of the CKM matrix is implemented. In addition, it was considered that the left-right symmetry is manifest, that is the left and right MNS and CKM mixing matrices are coincident. However, this can be generalized directly.

The model contains ten physical Higgs bosons: four neutral CP-even higgs bosons, one (the lightest) of which is considered to be the SM-like one with mass fixed to have the value mh=125 GeV. Four charged Higgs bosons and two CP-odd pseudoscalar Higgs bosons. The mass spectrum is calculated and the rotation matrices are implemented analytically.

Minimization conditions and spectrum relations are all used to express the whole model parameters and spectra in terms of only five independent (external) parameters: tanbeta, lambda_2, lambda_3, alpha_1, alpha_2. As in any two-Higgs doublet model, e.g., MSSM, tanbeta is the ratio between two vevs. The parameters lambda_2, lambda_3, alpha_1, alpha_2 are dimensionless potential parameters. The charged Higgs masses are implemented as external parameters.

The effective loop-induced h->gg and h->gammagamma, Zgamma, ZZ decays were added. For the complete pp->gammagamma analysis, Madgraph is used for generating events, Pythia is used for parton showering (PS), matrix element (ME) and PS merging, hadronization and jet matching and Madanalysis is used for event file analysis, recasting the LHC results and to produce this histogram figure (to be improved):


  1. Mustafa Ashry, TeV-scale left-right symmetric model with minimal Higgs sector, Master Thesis, Cairo University, Cairo (2015), Egypt (
  2. M. Ashry and S. Khalil, Phenomenological aspects of a TeV-scale alternative left-right model, Physical Review D 91, 015009 (2015) (arXiv:1310.3315) (


For the CalcHEP files, it's advised to use those uploaded to the page ( and not to reproduce them again from the model files. In the latter case, you will be faced by a conflict between the string size produced by FeynRules and this allowed by CalcHEP. In fact, those CalcHEP files uploaded to the page are general and there is no need to produce them again, unless you have modified the model itself and want to generate the new ones.


Special thanks to W. Abdallah; being revised the CalcHEP files and fixed the string size errors manually. The author would like to thank W. Abdallah, the late colleague A. Elsayed and A. Moursy for their helpful hints and useful discussions. Thanks to Prof. M. E. Peskin and Dr. B. Fucks for replying the questions and for their guiding notes.

Attachments (10)