Abstract
We study a classically scale-invariant model with an electroweak singlet complex scalar mediator together with an anomaly free set of two fermionic dark matters. We introduce $U(1{)}_{X}$ gauge symmetry with a new charge $X$ in the dark sector in order to stabilize the mass of the scalar singlet with a new gauge boson. Our conformally invariant scalar potential generates the electroweak symmetry breaking via the Coleman-Weinberg mechanism, and the new scalar singlet acquires its mass through radiative corrections of the fermionic dark matters and the new gauge boson as well as of the SM particles. Taking into account the collider bounds, we present the allowed region of new physics parameters satisfying the recent measurement of relic abundance. With the obtained parameter sets, we predict the elastic scattering cross section of the new singlet fermions into target nuclei for a direct detection of the dark matter. We also discuss the collider signatures and future discovery potentials of the new scalar and gauge boson.
Highlights
The discovery of a Higgs-like boson with ∼125 GeV mass at the Large Hadron Collider (LHC) completes the Standard Model (SM) particle spectrum [1,2]
The so-called naturalness problem essentially states that the Higgs mass parameter seems unnaturally small compared to the Planck scale at which the SM or physics beyond the SM at the electroweak scale is unified with the gravitational theory
We investigated an extension of the SM which is renormalizable and classically scale invariant
Summary
The discovery of a Higgs-like boson with ∼125 GeV mass at the Large Hadron Collider (LHC) completes the Standard Model (SM) particle spectrum [1,2]. − VSðH; SÞ − VFðψ1;2; SÞ; ð1Þ with the scale-invariant Higgs portal potential, VSðH; SÞ 1⁄4 λhðH†HÞ2 þ λhsH†HjSj2 þ λsjSj4; ð2Þ and with the DM Yukawa interaction, VFðψ ; SÞ 1⁄4 g1Sψ 1Lψ 1RS þ g2Sψ 2Lψ 2RSÃ þ H:c:; ð3Þ where giS are the DM Yukawa couplings, and we assume g1S 1⁄4 g2S 1⁄4 gS for simplicity those are not necessarily the same in general As such, those DM fermions have the same mass and the equal portion in the relic abundance of the Universe. The mixing angle tan θ is expected to be very small (less than about 0.3 depending on the h2 mass) due to the Large Electron-Positron (LEP) collider constraints [74] Through this scalar mixing θ, there is a kinetic mixing between Uð1ÞX and the SM Uð1ÞY gauge bosons arising in loop-level processes. Note that we have discarded some of the scalar interaction terms in the potential in Eq (12) by imposing the constraints in Eq (7)
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