Version 196 (modified by mashry, 3 years ago) (diff)


Alternative Left-Right Symmetric Model


Mustafa Ashry

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


mustafa[AT] mashry[AT]

Model Description

The Alternative Left-Right Symmetric Model (ALRM) is gauged by the Left-Right 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; causing the absence of the tree-level flavor-changing neutral currents mediated by Higgs bosons.

As in the SM, left-handed fermions compose SU(2)L doublets. Right-handed charged leptons form SU(2)R doublets with corresponding extra particles (scotinos) and right-handed up-quarks form SU(2)R doublets with corresponding extra down-type exotic quarks. Right-handed 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 SM electroweak symmetry is broken down to the U(1)em through the bidoublet and the SU(2)L-doublet vevs. Accordingly, all fermions 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, analogous to those of the SU(2)L 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 spectra are 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, lambda2, lambda3, alpha1, alpha2. As in any two-Higgs doublet model, e.g., MSSM, tanbeta is the ratio between two vevs. The parameters lambda2, lambda3, alpha1, alpha2 are dimensionless potential parameters. The charged Higgs masses are implemented as external parameters.

The effective loop-induced h->gluongluon and h->gammagamma decays at leading order (LO) were implemented. For the complete pp->gammagamma analysis, Madgraph is used as the monte carlo (MC) event generator (EG), Pythia is used for parton showering (PS), matrix element (ME) and PS merging, hadronization and jet matching, then Delphes is used as a detector simulator and finally Madanalysis is used for event file analysis, recasting the LHC results and to produce these histogram figures (to be improved):


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


For the CalcHEP files, it's advised to use those uploaded here ( rather than reproducing them again from the model file. In the latter case, you will be faced by a conflict from the ghost fields created by CalcHEP. Those CalcHEP files uploaded here 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.


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. B. Fuks and Prof. M. E. Peskin for their guiding notes.

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