Abstract
We present a new model that extends the Standard Model (SM) with the local B + L symmetry, and point out that the lightest new fermion ζ, introduced to cancel anomalies and stabilized automatically by the B + L symmetry, can serve as the cold dark matter candidate. We study constraints on the model from Higgs measurements, electroweak precision measurements as well as the relic density and direct detections of the dark matter. Numerical results reveal that the pseudo-vector coupling of ζ with Z and the Yukawa coupling with the SM Higgs are highly constrained by the latest results of LUX, while there are viable parameter space that could satisfy all the constraints and give testable predictions.
Highlights
The modelWhen the Standard Model (SM) is extended by the local B + L symmetry, anomalies are not automatically cancelled as in the minimal SM
The pseudo-vector coupling ζ with Z is suppressed by the latest PandaX-II result on the spin-dependent cross section, and the upper limit on this coupling is about 0.037
We present a new model that extends the Standard Model (SM) with the local B + L symmetry, and point out that the lightest new fermion ζ, introduced to cancel anomalies and stabilized automatically by the B + L symmetry, can serve as the cold dark matter candidate
Summary
When the SM is extended by the local B + L symmetry, anomalies are not automatically cancelled as in the minimal SM. One simple way out is to introduce, in addition to the right-handed neutrinos, extra vector-like fermions at the TeV scale so as to cancel various anomalies. To break the U(1)B+L gauge symmetry via the Higgs mechanism, we introduce a singlet scalar S with B + L charge of −6. It is easy to check that all potential anomalies are canceled in this simple framework, i.e. A1(SU(3)2C ⊗ U(1)B+L), A2(SU(2)2L ⊗ U(1)B+L), A3(U(1)2Y ⊗ U(1)B+L), A4(U(1)Y ⊗ U(1)2B+L), A5(U(1)3B+L) and A6(U(1)B+L). The most general Higgs potential takes the following form:. Trilinear scalar interactions are listed in table
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