Search for (Higgs-like) bosons decaying into a pair of long-lived exotic particles in the LHCb experiment

This thesis work presents a search for pairs of long-lived exotic particles originating from the decay of Higgs-like bosons. The search is performed using LHCb data corresponding to an integrated luminosity of 0.9 fb$^{-1}$. This study is motivated by many theoretical developments, beyond the Standard Model of particles physics, that predict the existence of non-yet discovered particles with lifetimes larger than those of B-hadrons. An analysis based on several theoretical models is presented and the background contribution is identified to originate from b quarks events. Total selection efficiencies in the range 0.1 to 0.7 % are obtained. No evidence for an event with the expected topology is found. For Higgs-like bosons masses in the range 100 to 125 GeV/c$^2$, for long-lived particles masses from 20 to 50 GeV/c$^2$ and for lifetimes from 5 to 50 ps, upper limits on production cross sections from 1 to 100 pb are obtained.