ETD system

Electronic theses and dissertations repository


Tesi etd-01112008-230127

Thesis type
Tesi di dottorato di ricerca
Study of Flavour Changing Neutral Currents in top quark decays with the CMS detector
Settore scientifico disciplinare
Corso di studi
Relatore Prof. Tonelli, Guido
Parole chiave
  • top decay
  • sensitivity
  • rare decays
  • new physics
  • LHC
  • FCNC
  • CMS
  • top quark
Data inizio appello
Riassunto analitico
This work contains an estimation of the observability of the Flavour Changing Neutral Currents (FCNC) in top decays with the CMS experiment at the future Large Hadron Collider.
The first realistic estimates for the experiment sensitivity to the decays t→Zq and t→γq (where q represents c or u-quarks) have been addressed, through the use of a full simulation of sub-detectors and reconstruction chain. Since expected branching ratios for top FCNC in the Standard Model are eagerly low, any experimental evidence for a top quark FCNC interaction would signal the existence of physics beyond the Standard Model.
A wide variety of Standard Model processes have been considered into background, and selection is optimized in order to maximize the significance in the signal region. A full set of systematic effects, originating from detector or theoretical uncertainties, are added to the simulation and their impact on the analysis is established. Efforts are pushed to find a specific control region for both analyses, that can be addressed in the future samples, thus allowing to measure directly the background when data will be available. Results are presented for several background levels and different experimental conditions, then extrapolated to the highest attainable LHC luminosities. An improvement of two orders of magnitude in sensitivity to FCNC branching ratio is obtained, allowing to shed light on different new physics scenarios.