We revisit the extraction of the triple electroweak gauge boson couplings from the Large Hadron Collider Run I data on the W þ W − and W AE Z productions when the analysis also contains additional operators that modify the couplings of the gauge bosons to light quarks and the gauge boson self-energies. We work in the framework of effective Lagrangians where we consider dimension-six operators and perform a global fit to consistently take into account the bounds on these additional operators originating from the electroweak precision data. We show that the constraints on the Wilson coefficients f B =Λ 2 and f W =Λ 2 are modified when we include the additional operators while the limits on f WWW =Λ 2 remain unchanged.

We address the question of deviations from 3 × 3 unitarity of the leptonic mixing matrix showing that, in the framework of type I seesaw mechanism, one may have significant deviations from unitarity that can be detected at the next round of experiments while some of the heavy neutrino masses are sufficiently low to become within experimental reach. For that purpose we introduce a specially useful parametrisation that enables to control all deviations of unitarity through a single 3 × 3 matrix, which we denote by X and which connects the mixing of the light and heavy neutrinos in the context of type I seesaw. We show that there is no need for the Yukawa couplings to be extremely suppressed. We present specific examples where deviations from 3 × 3 unitarity are sufficiently small to conform to all the present stringent experimental bounds.

In minimal lepton flavour violation Type-III see-saw models the flavour structure of the couplings of the triplet fermions to the Standard Model leptons can be reconstructed from the neutrino mass matrix and lepton number violation is very suppressed. Here, we explore the possibility of imposing bounds on this class of models with results of existing LHC searches and we quantify how the information on flavour and charge of the produced leptons is important for maximal sensitivity. With this aim we obtain the bounds which can be derived from the Run I search for events which contain two charged leptons (either electron or muons of equal or opposite sign), two jets from a hadronically decaying W boson and large missing transverse momentum. We find that using the information on charge and flavour of the leptons in the above final state it is possible to unambiguously rule out this scenario with triplet masses lighter than 300 GeV at 95% CL. The same analysis allows to exclude triplet masses up to 480 GeV at 95% CL for normal ordering of neutrino masses and specific values of a Majorana CP phase currently undetermined by neutrino physics. We also show that it is not possible to put an unambiguous bound on the mass of the new states if the flavor and charge information is not condsidered.

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