Dissertation committee:
Χριστίνα Κουρκουμέλη Καθηγήτρια (Επιβλέπουσα), Αλέξανδρος Καρανίκας Αναπληρωτής Καθηγητής, Δημήτριος Φασουλιωτης Επίκουρος Καθηγητής
Summary:
The first results on the search for a new heavy, neutral boson in the ATLAS
experiment, through its decay into a muon pair (Z’aμ+μ-), are presented. The
results include the first 42pb-1 of data from proton-proton collisions
collected during 2010 from the LHC at CERN and data collected in 2011, of a
total luminosity of 1,21 fb-1.
The thesis begins with a theoretical introduction on the models predicting the
existence of the new bosons. Then the ATLAS detector is described, followed by
the muon reconstruction and analysis methods used and the system performance.
The last part of the thesis presents the analysis performed on the real data.
The selection of the muon pairs is described, presenting the quality criteria
that were applied, to the real data and the simulated Z’ signals, as well as to
the background processes.
The irreducible background is the Drell-Yan process to muons. Other processes
that were studied include the ttbar, the W + jets (where a jet may be
misidentified as a muon), the di-boson production (WW, WZ and ZZ) and finally
the QCD processes bbbar and ccbar into muons. The distribution of the invariant
mass of the muon pairs was used to conclude whether there is an excess of
events in the data, in comparison with the expectations of the background.
The data of both years showed no excess of the data events above the
expectations. Using the data of 2010, the limit to the mass of Z 'was
calculated equal to 874GeV/c2. The data of 2011 extended this limit to 1,682
TeV/c2.
Keywords:
ATLAS, CERN, Z', Boson, Muon
