Résumé
Originally motivated for the generation of (Majorana) neutrino masses, the Type 2 Seesaw Modelhas also a rich extended Higgs sector with, if accessible at the LHC, a distinctive phenomenologyof neutral, charged and doubly-charged states. The goal of the work is to present an exhaustivephenomenological study of the most promising production and decay channels of pair or associatedscalars, decaying directly or in cascades to Standard Model particles at the LHC. The study iscomplementary to the literature in that it highlights a previously unnoticed important sensitivity toa mixing angle. The ensuing uncertainty calls for a comprehensive experimental search strategy forthe various processes. These processes can be studied within LHC energies reach, by comparingcutflow results for different final states. We carried out prospective search analyses with multi-lepton, jets and missing energy configurations, assuming an ATLAS-like detector at LHC andHL-LHC, for charged, doubly-charged, and for the first time neutral scalar productions. Thework is a collaboration between ATLAS experimentalists and theoreticians in continuation ofan endeavor that lead to previous published ATLAS analyses for the search of (doubly)chargedHiggs bosons [1, 2], aiming at proposals for future experimental searches. This proceeding onlysummarizes some of the results, and the reader is encouraged to consult the extended work [3] forfurther detailing the content of each section.