New dark matter candidates in various models beyond the standard model

Abstract

We study two different extensions of the Standard Model (SM) which provide interesting dark matter candidates. First, we consider a strongly interacting hidden sector where vector-like quarks live with new strong gauge bosons. Like QCD in the SM, the new scale $\Lambda_h$ naturally emerges from renormalization group running effect of the new gauge coupling in the strong sector, and it can generate electroweak symmetry breaking (EWSB) scale. Though we do not write the Higgs mass term in the SM Lagrangian by imposing the classical scale symmetry in the SM sector, the scale $\Lambda_h$ can give the effective mass term of Higgs and trigger EWSB. Moreover, this model gives a good cold dark matter (CDM) candidate, the hidden sector pion, which is stable from the accidental global symmetry of the hidden quark sector. We study collider phenomenology of the model and examine the relic density and the direct detection rate of the CDM candidate. We also study the singlet-extension of this model, in which the added singlet field makes the full Lagrangian classically scale symmetric so that all the mass scales are generated quantum mechanically. Second, we consider a model with multiple dark matters in the framework of U(1)`-extended the Minimal Supersymmetric Standard Model (MSSM). Adding a new U(1) symmetry to MSSM is well-motivated since it can cure several problems in the MSSM such as the $\mu$-problem and the proton decay problem from higher dimensional operators. After spontaneous breaking of the U(1)` symmetry, the residual discrete symmetry may remain in the theory. We study the simplest case where the residual symmetry is $Z_2$ (U-parity). The lightest U-parity particle (LUP) is stable under the new parity, and it could be a new dark matter candidate. The U-parity accompanied by the R-parity can allow up to three stable particles. We numerically illustrate that multiple stable particles in our model can satisfy both constraints from the relic density and...