Observable seesaw and its collider signatures

We discuss the scenario with TeV-scale right-handed neutrinos, which are accessible at future colliders, while holding down tiny seesaw-induced masses and sizable couplings to the standard-model particles. The signal with tri-lepton final states and large missing transverse energy is appropriate for studying collider signatures of the scenario with extra spatial dimensions. We show that the LHC experiment generally has a potential to discover the signs of extra dimensions and the origin of small neutrino masses.     

ALPs effective field theory and collider signatures

We study the leading effective interactions between the Standard Model fields and a generic singlet CP-odd (pseudo-) Goldstone boson. Two possible frameworks for electroweak symmetry breaking are considered: linear and non-linear. For the latter case, the basis of leading effective operators is determined and compared with that for the linear expansion. Associated phenomenological signals at colliders are explored for both scenarios, deriving new bounds and analyzing future prospects, including LHC and High Luminosity LHC sensitivities. Mono-Z, mono-W, W-photon plus missing energy and on-shell top final states are most promising signals expected in both frameworks. In addition, non-standard Higgs decays and mono-Higgs signatures are especially prominent and expected to be dominant in non-linear realisations.     

Electroweak vacuum stability and diphoton excess at 750 GeV

Recently,both ATLAS and CMS collaborations at the CERN Large Hadron Collider(LHC) announced their observations of an excess of diphoton events around the invariant mass of 750 GeV with a local significance of 3.6σ and 2.6σ,respectively.In this paper,we interpret the diphoton excess as the on-shell production of a real singlet scalar in the pp →S→γγ channel.To accommodate the observed production rate,we further introduce a vector-like fermion F,which carries both color and electric charges.The viable regions of model parameters are explored for this simple extension of the Standard Model(SM).Moreover,we revisit the problem of electroweak vacuum stability in the same scenario,and find that the requirement for the electroweak vacuum stability up to high energy scales imposes serious constraints on the Yukawa coupling of the vector-like fermion and the quartic couplings of the SM Higgs boson and the new singlet scalar.Consequently,a successful explanation for the diphoton excess and the absolute stability of electroweak vacuum cannot be achieved simultaneously in this economical setup.     

Signatures and possible evidence for supersymmetry at the CERN collider

For certain ranges of masses of the supersymmetric partners of the gluons, quarks and W-bosons, it is expected that a few events of production and decay of the partners could be observed at the CERN pp? collider. The characteristic signatures are events with $\text{?±}\text{j}\textcolor{red}{}\text{, ?±}\text{jj}\textcolor{red}{}\text{,}\text{jjj}\textcolor{red}{}\text{,}\text{jj}\textcolor{red}{}\text{and j}\textcolor{red}{}$ where ?^± is an isolated charged lepton, j is a hadron jet and

stands for missing p_T. Some recently reported events are of this type.     

Scalar Resonance at 750 GeV as Composite of Heavy Vector-Like Fermions

We study a model of scalars which includes both the SM Higgs and a scalar singlet as composites of heavy vector-like fermions. The vector-like fermions are bounded by the super-strong four-fermion interactions. The scalar singlet decays to SM vector bosons through loop of heavy vector-like fermions. We show that the surprisingly large production cross section of di-photon events at 750 GeV resonance and the odd decay properties can all be explained. This model serves as a good model for both SM Higgs and a scalar resonance at 750 GeV.