O. Panella

Signals of heavy Majorana neutrinos at hadron colliders

The lepton number violating signal of like-sign-dileptons (LSD), p p \to \ell^\pm\ell^\pm + 2 jets, is investigated within a model of mixing in the neutrino sector assuming the existence of heavy Majorana neutrino states with a left--handed coupling to the light leptons. The LSD signal receives contributions both from the resonant production of a heavy Majorana neutrino (N) and from the exchange of a virtual N in the WW fusion mechanisms. These two possibilities are discussed in detail and compared. Helicity amplitudes are given pointing out differences with calculations previously reported by other authors. The signal cross--sections are computed at the energy of the LHC collider (sqrt{S}=14 TeV) at CERN and within the existing experimental limits on the mixing couplings, including those coming from neutrinoless double beta decay. Detailed angular distributions of signal reactions which are complementary to previous studies on the argument are presented.

Phenomenology of excited doubly charged heavy leptons at LHC

We consider the production at the LHC of exotic composite leptons of charge Q = +2e. Such states are allowed in composite models which contain extended isospin multiplets (IW = 1 and IW = 3/2). These doubly charged leptons couple with Standard Model [SM] fermions via gauge interactions, thereby delineating and restricting their possible decay channels. We discuss the production cross section at the LHC of L ++ (pp → L ++ , l − ) and concentrate on the leptonic signature deriving from the cascade decays L ++ → W + l + → l + l + νl i.e. pp → l − (l + l + ) νl showing that the invariant mass distribution of the like-sign dilepton has a sharp end point corresponding to excited lepton mass m ∗ . We find that the √ s = 7 TeV run is sensitive at the 3-sigma (5-sigma) level to a mass of the order of 600 GeV if L = 10 fb −1 (L = 20 fb −1 ). The √ s = 14 TeV run can reach a sensitivity at 3-sigma (5-sigma) level up to m ∗ = 1 TeV for L = 20 fb −1 (L=60 fb −1 ).

Hunting for heavy composite Majorana neutrinos at the LHC

We investigate the search for heavy Majorana neutrinos stemming from a composite model scenario at the upcoming LHC Run II at a centre of mass energy of 13 TeV. While previous studies of the composite Majorana neutrino were focussed on gauge interactions via magnetic type transition coupling between ordinary and heavy fermions (with mass

Lepton flavor violation ine±e−→l±e−(l=μ,τ)induced byR-conserving supersymmetry

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Doubly charged heavy leptons at LHC via contact interactions

m∗) here we complement the composite model with contact interactions at the energy scale

Leptogenesis and composite heavy neutrinos with gauge mediated interactions

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