Scale-Invariant Two Component Dark Matter

We study a scale invariant extension of the standard model which can explain simultaneously dark matter and the hierarchy problem. In our set-up, we introduce a scalar and a spinor as two-component dark matter in addition to scalon field as a mediator. Interesting point about our model is that due to scale invariant conditions, compared to other two-component dark matter models, it has lower independent parameters. Possible astrophysical and laboratory signatures of two-component dark matter candidate are explored and it is shown that the most contribution of observed relic density of dark matter can be determined by spinor dark matter. Detectability of these dark matter particles is studied and the direct and invisible Higgs decay experiments are used to rule out part of the parameter space of the model. In addition, the dark matter self-interactions are considered and shown that their contribution saturate this constraint in the resonant regions.Comment: 22 pages, 14 figure

Impact of Torsion Space-Time on ttˉt\bar{t} observables at Hadron Colliders

Starting from the effective torsion space-time model, we study its effects on the top pair production cross section at hadron colliders. We also study the effect of this model on top pair asymmetries at the Tevatron and the LHC. We find that torsion space-time can explain forward-backward asymmetry according to measured anomaly at Tevatron. We find an allowed region in the parameters space which can satisfy simultaneously all $t\bar{t}$ observables measured at Tevatron and LHC.Comment: 17 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1207.064

W-boson mass anomaly and vacuum structure in vector dark matter model with a singlet scalar mediator

Motivated by the deviation of the W boson mass reported by the CDF collaboration, we study an extension of the Standard Model (SM) including a vector dark matter (VDM) candidate and a scalar mediator. In the model, the one-loop corrections induced by the new scalar, shift the W boson mass. We identify the parameter space of the model consistent with dark matter (DM) relic abundance, W mass boson anomaly, invisible Higgs decay at LHC, and direct detection of DM. It is shown that the W-mass anomaly can be explained for the large part of parameter space of VDM mass and scalar mediator mass between $100-124~\rm GeV$ by the model. We also investigate the renormalization group equations (RGE) at one-loop order for the model. We show that the contribution of new scalar mediator to RGE, guarantees positivity and vacuum stability of SM Higgs up to Planck scale

Probing the top quark chromoelectric and chromomagnetic dipole moments in single top tWtW-channel at the LHC

We study the effects of chromoelectric and chromomagnetic dipole moments (CEDM and CMDM) on the production cross section of single top $tW$-channel at the LHC based on the effective Lagrangian approach. We show that the impact of CEDM and CMDM could be large. Using the experimental measurement of the $tW$-channel cross section, constraints on CEDM and CMDM are extracted. These constraints are comparable with the ones obtained from the top pair analysis.Comment: 13 pages, 4 figure

Conformal vector dark matter and strongly first-order electroweak phase transition

We study a conformal version of the Standard Model (SM), which apart from SM sector, containing a $U_{D}(1)$ dark sector with a vector dark matter candidate and a scalar field (scalon). In this model the dark sector couples to the SM sector via a Higgs portal. The theory is scale-invariant in lowest order, therefore the spontaneous symmetry breaking of scale invariance entails the existence of a scalar particle, scalon, with vanishing zeroth-order mass. However, one-loop corrections break scale invariance, so they give mass to the scalon. Because of the scale invariance, our model is subjected to constraints which remove many of the free parameters. We put constraints to the two remaining parameters from the Higgs searches at the LHC, dark matter relic density and dark matter direct detection limits by PandaX-II. The viable mass region for dark matter is about 1-2 TeV. We also obtain the finite temperature one-loop effective potential of the model and demonstrate that finite temperature effects, for the parameter space constrained by dark matter relic density, induce a strongly first-order electroweak phase transition.Comment: 27 pages, 7 figures, a few clarifications added, references updated, version published in JHE