Doubly charged scalars often appear in Standard Model extensions motivated by mechanisms for neutrino mass generation. Within a general framework, the interactions of a doubly charged scalar with charged leptons allow for lepton flavour violation (LFV), therefore receiving significant bounds from low-energy LFV experiments. In the first part of this seminar I will briefly present the low-energy effective field theory for these models and review the present limits. Moreover, I will recall the current status of the LHC searches and present future perspectives for the HighLumi LHC phase and for future e+e- colliders. Finally, I will show how these different bounds from low- and high-energy physics need to be combined to get a coherent picture.
The second part of the seminar will be devoted to other Beyond the Standard Model (BSM) scenarios, where singly and doubly charged bosons may appear as decay products of heavy exotic quarks. Model-independent results obtained in the framework of a simplified model will be briefly shown and reinterpreted, as a case study, as bounds for the parameters of the 331 Model, a class of BSM models with extended gauge symmetry. To conclude, a digression will be devoted to the determination of mathematical constraints that the scalar potential of such models are required to fulfil, and that promise to have a strong impact on the parameter space of the model.
