This thesis presents innovative contributions to the CMS experiment in the new trigger system
for the restart of the LHC collisions in Run II as well as original analysis methods and
important results that led to official publications of the Collaboration.The author's novel
reconstruction algorithms deployed on the Field-Programmable Gate Arrays of the new CMS
trigger architecture have brought a gain of over a factor 2 in efficiency for the
identification of tau leptons with a very significant impact on important H boson measurements
such as its decays to tau lepton pairs and the search for H boson pair production.He also
describes a novel analysis of HH bb tautau a high priority physics topic in a difficult
channel. The original strategy optimisation of event categories and the control of the
background have made the result one of the most sensitive concerning the self-coupling of the
Higgs boson among all possible channels at the LHC.
