No Arabic abstract
We investigate the predictions of a simple extension of the Standard Model where the Higgs sector is composed of one $SU(2)_L$ doublet and one real triplet. We discuss the general features of the model, including its vacuum structure, theoretical and phenomenological constraints, and expectations for Higgs collider studies. The model predicts the existence of a pair of light charged scalars and, for vanishing triplet vacuum expectation value, contains a cold dark matter candidate. When the latter possibility occurs, the charged scalars are long-lived, leading to a prediction of distinctive single charged track with missing transverse energy or double charged track events at the LHC. The model predicts a significant excess of two-photon events compared to SM expectations due to the presence of a light charged scalar.
It is well known that for the pure standard model triplet fermionic WIMP-type dark matter (DM), the relic density is satisfied around 2 TeV. For such a heavy mass particle, the production cross-section at 13 TeV run of LHC will be very small. Extending the model further with a singlet fermion and a triplet scalar, DM relic density can be satisfied for even much lower masses. The lower mass DM can be copiously produced at LHC and hence the model can be tested at collider. For the present model we have studied the multi jet ($geq 2,j$) + missing energy ($cancel{E}_{T}$) signal and show that this can be detected in the near future of the LHC 13 TeV run. We also predict that the present model is testable by the earth based DM direct detection experiments like Xenon-1T and in future by Darwin.
We consider a scenario where an SU(2) triplet scalar acts as the portal for a scalar dark matter particle. We identify regions of the parameter space, where such a triplet coexists with the usual Higgs doublet consistently with all theoretical as well as neutrino, accelerator and dark matter constraints, and the triplet-dominated neutral state has substantial invisible branching fraction. LHC signals are investigated for such regions, in the final state {em same-sign dilepton + $ge$ 2 jets + $ ot E_T$.} While straightforward detectability at the high-luminosity run is predicted for some benchmark points in a cut-based analysis, there are other benchmarks where one has to resort to gradient boosting/neural network techniques in order to achieve appreciable signal significance.
Elements of the phenomenology of color-octet scalars (sgluons), as predicted in the hybrid N=1/N=2 supersymmetric model, are discussed in the light of forthcoming experiments at the CERN Large Hadron Collider.
Effective field theory (EFT) formulations of dark matter interactions have proven to be a convenient and popular way to quantify LHC bounds on dark matter. However, some of the non-renormalizable EFT operators considered do not respect the gauge symmetries of the Standard Model. We carefully discuss under what circumstances such operators can arise, and outline potential issues in their interpretation and application.
While the paradigm of a weakly interacting massive particle (WIMP) has guided our search strategies for dark matter in the past decades, their null-results have stimulated growing interest in alternative explanations pointing towards non-standard signatures. In this article we discuss the phenomenology of dark matter models that predict long-lived particle at the LHC. We focus on models with a $Z_2$-odd dark sector where - in decreasing order of the dark matter coupling - a coannihilation, conversion-driven freeze-out or superWIMP/freeze-in scenario could be realized.