Dissertation committee:
Δημήτριος Φασουλιώτης Αναπλ. Καθηγητής (Επιβλέπων), Χριστίνα Κουρκουμέλη Καθηγήτρια, Βενέτιος Πολυχρονάκος Διευθυντής Ερευνών
Summary:
This dissertation presents the search for Higgs-like bosons, in the decay mode
H->ZZ(*)->llqq, using data collected with the ATLAS detector, at the CERN Large
Hadron Collider (LHC). Despite the fact that this channel is mostly sensitive
in the Higgs boson mass range above 200 GeV, before the discovery of the
Standard Model Higgs boson the search was extended over the mass interval
120-180 GeV. Reasonable sensitivity is observed above 140 GeV. The search uses
4.7~fb^-1 of proton–proton collision data, at a centre-of-mass energy of 7 TeV.
After the discovery of the Higgs boson, the search focused towards the
detection of additional, heavy Higgs bosons, in the mass range 200-1000 GeV.
Proton–proton collision data, at a centre-of-mass energy of 8 TeV, are used,
corresponding to an integrated luminosity of 20.3 fb^-1. Since no significant
excess of events is observed over the Standard Model prediction, upper limits
are set, at 95\% confidence level (CL), on the production cross-section of a
heavy Higgs boson times the branching ratio of its decay mode to a pair of Z
bosons. Finally, exclusion limits are estimated by the combined statistical
interpretation of the results of the H->ZZ: ZZ->llqq, ZZ->llll, ZZ->llvv and
ZZ->vvqq search channels, over the Higgs boson mass range 140-1000 GeV.
Keywords:
Higgs, llqq, ATLAS, Standard Model, LHC
