Search for Higgs bosons decaying to tau leptons with the CMS experiment at the LHC
(2015)
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- Authors
- Supervisors
- Bruno, Giacomo
- Abstract
- With the first LHC proton-proton (p-p) collisions at a center-of-mass energy of 7 TeV occurred in spring 2010, the world witnessed the beginning of a new era in particle physics. From that milestone onward, the Standard Model (SM), the theory that describes matter constituents and their interactions, has been further verified and a large number of searches for new phenomena have been performed. The SM foresees the existence of the Higgs boson, which is the particle that gives mass to fermions and gauge bosons. The discovery of a SM Higgs-like particle in bosonic channels has been announced on July 2012 by the ATLAS and CMS experiments at LHC. Signals of such a particle in the fermionic decay channels were, instead, still not revealed when the work presented in this thesis started. Moreover, it is known that the SM has limitations which might be explained by extended theoretical scenarios. This thesis has dealt on one side with finding traces, with the CMS experiment, of the SM Higgs boson decay in the fermionic channels and on the other with finding evidence of possible scenarios beyond the SM. In the former context, the search for the SM Higgs boson h decaying into a pair of tau leptons and produced in association with a Z boson decaying into either a dielectron or dimuon pair, has been performed. By combining the result of this search with a few others, evidence for the decay of the newly discovered particle in the ditau channel has been found, demonstrating its Higgs-like nature as predicted by the SM. In the second part of the thesis, a search for a new resonance decaying to a Z boson and a lighter resonance, as predicted by models with two Higgs doublets (2HDM, which are extensions of the SM), has been performed. The decay of the Z boson into dilepton pairs and that of the light resonance into a pair of tau leptons have been considered. With no significant excess observed over expected backgrounds, 95% confidence level (CL) exclusion limits on the signal cross section have been set. The performance of the algorithm used in the CMS experiment to reconstruct and identify tau leptons, crucial for the analyses presented in this thesis, have also been widely studied and presented in this manuscript.
- Affiliations
Citations
Perrini, L. (2015). Search for Higgs bosons decaying to tau leptons with the CMS experiment at the LHC. https://hdl.handle.net/2078.5/78524