In this Thesis a search for Higgs boson production has been performed analysing data gathered by the Collider Detector at Fermilab (CDF) from proton-antiproton (p$\bar{p}$) collisions at the center of mass energy √s = 1.96 TeV. Event selection has been optimized on Higgs decaying into W+W- bosons in order to reconstruct final states with two charged leptons formed by either an electron and a tau or a muon and a tau focusing on taus decaying into hadrons. No evidence of Higgs production has been found analysing 4.8 fb-1 of data and an up- per limit has been set on the production cross section as a function of the mass mH in the range from 130 to 200 GeV/c2 with a 95% Confidence Level. For a Higgs mass hypothesis of 160 GeV/c2 the observed limit is 33.5 times the Standard Model predicted cross section [sigma]SM while the expected upper limit for the same mass is 19.6×[sigma]SM. The high recorded luminosity along with the development of new analysis techniques are expected to improve the CDF sensitivity to the search for Higgs boson with hadronic taus reconstructed in the final state, in the mass range 130 to 200 GeV/c2.

A search for the decay of a light Higgs boson to a pair of weakly-interacting, long-lived particles in 20.8 fb-1 of proton-proton collisions at [square root of] s = 8 TeV recorded in 2012 by the ATLAS detector is presented. The strategy requires that both of the long-lived particles decay just before or inside the hadronic calorimeter. No statistically significant excess of events is observed above the expected background and limits on the Higgs boson production and branching ratio to weakly-interacting, long-lived particles are derived as a function of the particle's proper decay length.

The Standard Model predicts the existence of one neutral scalar Higgs boson, which is a remnant of the mechanism that breaks the SU(2)[sub L]xU(1)[sub Y] electroweak symmetry and generates masses for the heavy vector bosons and fermions. Many extensions to the Standard Model predict two or more Higgs doublets, resulting in a larger spectrum of Higgs bosons including a charged Higgs boson (H[sup [+-]]). For a light charged Higgs boson mass, the top decay into a charged Higgs boson and bottom quark might occur. This thesis presents results of a direct search for this top quark decay mode via the charged Higgs decay to a tau lepton and tau-neutrino, using the hadronic decays of the tau leptons. The search data consist of 100 pb[sup -1] of Run 1 data collected between 1992-1995 at the CDF detector, from p[anti p] collisions at a center-of-mass energy of 1.8 TeV produced at Fermilab's Tevatron accelerator. A total of seven events are observed in two search channels with an expected background contribution of 7.4[+-]2.0 events coming from fake taus (5.4[+-]1.5), heavy vector boson decays with jets (1.9[+-]1.3) and dibosons(0.08[+-]0.06). Lacking evidence for a signal, we set limits on charged Higgs production at the 95% confidence level in the charged Higgs mass plane versus tan[beta](a parameter of the theory) for a top quark mass of 175 GeV/c[sup 2] and for top production cross sections ([sigma][sub t[anti t]]) of 5.0 and 7.5 pb, assuming the Type-II Two-Higgs-Doublet-Model. For large tan[beta], this analysis excludes a charged Higgs boson of mass below 147(158)GeV/c[sup 2] for [sigma][sub t[anti t]]=5.0(7.5)pb. Using the Standard Model measured top quark cross section from CDF, this limit increases to 168 GeV/c[sup 2] and we also exclude a branching fraction of top decays via this charged Higgs mode of greater than 43% for charged Higgs masses below 168 GeV/c[sup 2].

In this Thesis the electro-weak spontaneous symmetry breaking of the Standard Model (SM) is studied by searching for the scalar Higgs particle in the proton antiproton collisions of the Tevatron collider, at the center of mass energy √s = 1.96 TeV. We report on the inclusive search for the Higgs boson decaying to two W bosons in the final state characterized by two charged leptons (e or [mu]) and two neutrinos. The analysis of 4.8 fb$^{-1}$ of data recorded by the Collider Detector at Fermilab (CDF) shows no evidence of its production. We set 95% Confidence Level upper limits on the production cross section as a function of the mass $m_H$ in the range 110 to 200 GeV/$c^2$. For $m_H$ = 165 GeV/$c^2$ the observed limit is 1.3 times the SM predicted cross section ([sigma]H); the expected limit, in absence of signal, is 1.2+0.6 -0.4[sigma](H). These limits are the most stringent ones set by a single experiment up to date, for $m_H$ > 130 GeV/c2.