ETD system

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Tesi etd-10252012-120538


Thesis type
Tesi di dottorato di ricerca
Author
SFORZA, FEDERICO
URN
etd-10252012-120538
Title
Evidence for Diboson Production in the Lepton plus Heavy Flavor Jets Final State at CDF
Settore scientifico disciplinare
FIS/04
Corso di studi
FISICA
Commissione
tutor Dott. Chiarelli, Giorgio
commissario Tonelli, Guido
commissario Grivaz, Jean-Francois
commissario Cobal, Marina
commissario Busetto, Giovanni
Parole chiave
  • hadron collider
  • diboson
  • CDF
  • lepton plus jets
  • SVM
Data inizio appello
29/10/2012;
Consultabilità
completa
Riassunto analitico
The topic of this thesis is the measurement of W and Z bosons associate production in the lepton (l) plus neutrino (nu) plus Heavy Flavor (HF) quarks final state identified by the CDF II experiment at the Tevatron collider at s^1/2=1.96 TeV.<br><br>The fist evidence at hadron colliders of diboson production in such final state is reported.<br><br>The CDF II experiment set tight constraints on the existence of the Higgs boson with most of the sensitivity (for the low mass Higgs boson) coming from a very similar final state to the one studied in this thesis (WH -&gt; l nu+b bbar). Thus it is possible to test the correctness of the analysis procedure used in the Higgs search. <br><br>The actual analysis procedure is divided in several steps: object identification, background estimate and statistical analysis. <br><br>First, a set of advanced identification algorithms is exploited for the recognition of the final state objects: one charged lepton a neutrino, and two high energy jets, of which at least one tagged by the identification of the secondary decay vertex produced by a HF hadron. <br><br>Between the specific event selection requirements an original technique, based on the support vector machine algorithm was developed to suppress the multi-jet events, a background, difficult to model, due to events in which no real W -&gt; l nu decay is present.<br><br>Successively the total background is estimated with a variety of methods (both Monte Carlo and data driven). Finally a shape analysis of the di-jet invariant mass distribution and of a flavor-separator neural network distribution allowed the extraction of the combined diboson signal and the separate WW vs WZ/ZZ contributions.
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