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Tesi etd-01132009-171128

Thesis type
Tesi di dottorato di ricerca
Search for the Standard Model Higgs decaying into tau--jet final state with the ATLAS experiment at the LHC
Settore scientifico disciplinare
Corso di studi
Relatore Prof. Cavasinni, Vincenzo
Parole chiave
  • LHC
  • Higgs
  • tau
Data inizio appello
Riassunto analitico
The search for the Higgs boson is one of the primary goal of the ATLAS experiment at the LHC.<br>The mass of the Higgs boson is not predicted by the Standard Model theory of elementary particles.<br>Direct searches performed at the LEP experiments have excluded the mass region below 114 GeV.<br>Electroweak fits to the Standard Model parameters prefer a light Higgs boson, with a mass below 185 GeV at 95% C.L.<br>For the low mass region, above 114 GeV, the most promising channel for the discovery is the<br>production of the Higgs via Vector Boson Fusion and decaying into tau leptons.<br>In a previous analysis only the fully leptonic and the semi-leptonic decay modes of the tau pair<br>has been studied.<br>In this thesis work, for the first time, the fully hadronic final state is investigated.<br>Analysis has been performed with Monte Carlo data produced with the full simulation of the ATLAS detector.<br>Being a fully hadronic final state, the biggest challenge is to estimate the background form multijet QCD events.<br>Having a cross section many order of magnitude higher than the signal, its estimate cannot be obtained from Monte Carlo data in a direct<br>way due to the lack of statistics. To tackle this problem, a bigger sample of fast simulated QCD events has been used and a cut <br>factorization procedure has been<br>developed to get the final estimate.<br>Promising results have been obtained which are compatible with the existing ones for the fully <br>leptonic and the semi-leptonic decay modes in<br>terms of signal efficiency and background rejection, the latter with the exclusion of QCD multijet that <br>was not considered for these two final states.<br>