Tau leptons in the search for charged Higgs bosons

The Standard Model (SM) of particle physics, a gracefully crafted collection of particle theories, has made an astounding number of accurate predictions about the properties of particles and the fundamental laws that govern our universe. Among its long list of remarkable successes are the unification of the electromagnetic and weak forces, the prediction of elementary particles such as the Higgs boson, and its ability to precisely predict a wide range of particle cross-sections and branching fractions which have been verified experimentally.

Yet despite its immense predictive power, some major problems with the stan- dard model are its failure to accommodate dark matter and the gravitational force, as well as its inability to provide sources of CP violation large enough to produce the observed baryon asymmetry of our universe. It is apparent that extensions to the SM are required to account for these observed phenomena. Particle theorists have developed a plethora of such extensions to account for these observations, some of which include additional scalar particles as part of an extended Higgs sector. Ex- tending the SM by adding a second Higgs doublet either as an independent theory via Two Higgs Doublet Models (2HDM)s, or as part of a more expansive framework like Super Symmetry helps accommodate for some of these observed phenomena. Addi- tionally, an observed tension in lepton flavor universality giving rise to an excess of tau leptons can be explained by the existence of charged Higgs bosons decaying via $H^{\pm}\rightarrow\tau\nu$.

Because of its large branching fraction throughout a range of 2HDM parameter space, $H^{\pm}\rightarrow\tau\nu$ is an attractive decay channel for 2HDM-related searches. This thesis presents the search for charged Higgs bosons in a model-independent manner with a hypothesized mass between 80 and 3000 GeV through the ($H^{\pm}\rightarrow\tau\nu$) decay mode, as well as presents the contributions made in the development of the ATLAS collaboration’s Tau Identification Neural Network (TauID), a tool used by all the on collaboration to identify hadronically decaying taus.