CERN Accelerating science

Thesis
Report number	CERN-THESIS-2019-313
Title	Search for Diboson Resonances in the All-Hadronic Final State with the CMS Detector at √s= 13 TeV
Related title	Suche nach Zwei-Boson-Resonanzen im vollhadronischen Endzustand mit dem CMS-Detektor
Author(s)	Schäfer, Daniela (KIT, Karlsruhe)
Publication	2019. - 221 p.
Thesis note	PhD : KIT, Karlsruhe : 2019
Thesis supervisor(s)	Mozer, Matthias ; Mueller, Thomas
Note	presented 6 Dec 2019
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; CMS
Keywords	Diboson ; Resonance ; CMS
Abstract	A search for new resonances decaying to WW, WZ or ZZ in the all hadronic final state using 77.3 fb $^{−1}$ of data taken with the CMS experiment at the CERN LHC at a center-of-mass energy of 13 TeV is presented. The search focuses on potential new particles with a mass at the TeV scale resulting in a high transverse momentum of the produced vector bosons.The subsequent decay products of the vector bosons are therefore highly collimated and reconstructed into a single large-radius jet, which are further classified using jet substructure methods. The analysis presented utilizes a new data-driven background modeling technique based on a template fit in a three-dimensional hyperspace spanned by the dijet invariant mass and the corrected jet masses of the two final state jets. This method allows the utilization of the full available signal yield while simultaneously constraining the background processes by including the mass sideband regions in the fit. This grants the opportunity to easily expand this framework to include VH, HH or more exotic signals with different messenger particles in the future.No significant excess is observed above the estimated standard model background and limits are set at 95% confidence level on the cross section times branching fraction of a new particle,which are interpreted in terms of various models that predict spin-2 gravitons or spin-1 vector bosons. In a heavy vector triplet model, spin-1 Z' and W' resonances with masses below 3.5 and 3.8 TeV, respectively, are excluded at 95% confidence level. In a narrow-width bulkgraviton model, upper limits on cross sections times branching fractions are set between 27 and 0.2 fb for resonance masses between 1.2 and 5.2 TeV, respectively. The limits presented in this thesis are the best to date in the dijet final state.
Copyright/License	CC BY-SA 4.0

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