Abstract
We present a minimal extension of the left-right symmetric model based on the gauge group SU(3)c× SU(2)L× SU(2)R× U(1)B−L× U(1)X, in which a vector-like fermion pair (ζL and ζR) charged under the U(1)B−L× U(1)X symmetry is introduced. Associated with the symmetry breaking of the gauge group SU(2)R× U(1)B−L× U(1)X down to the Standard Model (SM) hypercharge U(1)Y, Majorana masses for ζL,R are generated and the lightest mass eigenstate plays a role of the dark matter (DM) in our universe by its communication with the SM particles through a new neutral gauge boson “X”. We consider various phenomenological constraints of this DM scenario, such as the observed DM relic density, the LHC Run-2 constraints from the search for a narrow resonance, and the perturbativity of the gauge couplings below the Planck scale. Combining all constraints, we identify the allowed parameter region which turns out to be very narrow. A significant portion of the currently allowed parameter region will be tested by the High-Luminosity LHC experiments.
Highlights
Where the U(1)X symmetry ensures the stability of the Dirac fermion and the dark matter (DM) fermion communicates with the Standard Model (SM) particles through the massive gauge boson X
We present a minimal extension of the left-right symmetric model based on the gauge group SU(3)c × SU(2)L × SU(2)R × U(1)B−L × U(1)X, in which a vector-like fermion pair charged under the U(1)B−L × U(1)X symmetry is introduced
Associated with the symmetry breaking of the gauge group SU(2)R × U(1)B−L × U(1)X down to the Standard Model (SM) hypercharge U(1)Y, Majorana masses for ζL,R are generated and the lightest mass eigenstate plays a role of the dark matter (DM) in our universe by its communication with the SM particles through a new neutral gauge boson “X”
Summary
As has been first proposed in ref. [20], the minimally extended LRSM is based on the gauge group GLRX ≡ SU(3)c × SU(2)L × SU(2)R × U(1)B−L × U(1)X. Note that the charge assignment for ζL,R : (−a/2, a/2) is crucial to generate Majorana mass terms for ζL,R, while (−b/2, b/2) with b = a is assigned in ref. The most general gauge bosons kinetic terms are given by Lgauge. The gauge symmetry GLRX is broken down to SU(3)c × U(1)em by the following vacuum expectation values (VEVs):. The sequence of the gauge symmetry breaking is as follows: first, the SU(2)R ×U(1)B−L symmetry is broken by vR, yielding large masses for WR and ZR. The U(1)X symmetry is broken by vX and the mass of U(1)X gauge boson is generated. The mass eigenvalues are given by M± = M ±m and corresponding eigenstates, ζ and ζh, are defined as PLζ. Thanks to the U(1)X symmetry, the lighter mass eigenstate ζ is stable and identified with the Majorana fermion DM.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
