Identification of b-jets in boosted H to bb decays and a study of the decay V0 to WH to lnubb in sqrt(s) = 13 TeV pp-collisions with the ATLAS detector

In the case of a boosted Higgs boson decaying to two b-quarks, the b-quark decay products can overlap. In boosted topologies the performance of standard b-tagging algorithms in ATLAS is diminished due to this overlap and the merging of close-by jets. In the first part of this thesis a b-tagging algorithm is presented which is optimized specifically for boosted H ! bb¯ decays using track jets with a smaller than standard radius. Track jets are expected to describe the b-hadron flight direction more closely than standard calorimeter jets. The use of jets with a smaller radius allows to resolve topologies where larger radius jets are already merged. Boosted Higgs bosons can originate from the decay of a hypothetical new heavy resonance. Many theories beyond the Standard Model predict such resonances. In the second part of this thesis a search analysis for a resonance in the decay channel V0± ! WH ! l⌫bb¯ is presented which is optimized such that it is ecient also for resonances with very high masses.