doctoral thesis
Miha Muškinja (Author), Borut Paul Kerševan (Mentor), Andrej Gorišek (Co-mentor)

Abstract

The thesis presents the advantage of using same-charge leptons in the final state in searches for new physics processes using proton–proton collisions recorded by the ATLAS detector at the LHC. The used data sample at a centre-of-mass energy of 13 TeV corresponds to $36.1$ $\mathrm{fb}^{-1}$ of integrated luminosity recorded in 2015 and 2016. Data-driven methods are derived to estimate the Standard Model background in same-charge channels up to transverse momenta of leptons of about $p_{\mathrm{T}}$ = 1 TeV. The Left-Right Symmetric Model is used as the benchmark beyond the Standard Model framework to optimize the analysis and to search for the production of doubly charged Higgs bosons ($H^{\pm\pm}$), heavy neutrinos ($N_{\mathrm{R}}$), and right-handed vector gauge bosons ($W_{\mathrm{R}}$). No significant evidence of a signal is observed and corresponding lower limits on the production cross-section are derived for the pair production of $H^{\pm\pm}$ bosons ($pp \to H^{++} H^{--}$) and for the Keung-Senjanovi\'c process ($pp \to \ell N_{\mathrm{R}} \to \ell \ell W_{\mathrm{R}} \to \ell \ell j j$). The observed limits of the two processes are the strongest to date and a novel method of parametrizing the electron charge misidentification probability is developed and used for the first time in the ATLAS Collaboration.

Keywords

experimental particle physics;elementary particles;ATLAS detector;proton collisions;new physics;Higgs boson;same-charge leptons;

Data

Language: English
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UL FMF - Faculty of Mathematics and Physics
Publisher: [M. Muškinja]
UDC: 539.1(043.3)
COBISS: 3240036 Link will open in a new window
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Downloads: 269
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Other data

Secondary language: Slovenian
Secondary title: Iskanje procesov nove fizike s pari enako nabitih leptonov v končnem stanju z detektorjem ATLAS
Secondary abstract: V doktorskem delu sem predstavil prednost uporabe parov enako nabitih leptonov v končnem stanju za iskanje procesov nove fizike s trki protonov z detektorjem ATLAS na LHC-ju. Podatki, uporabljeni v analizi, so bili zajeti med letoma 2015 in 2016 pri težiščni energiji 13 TeV in ustrezajo integrirani luminoznosti $36.1$ $\mathrm{fb}^{-1}$. Za oceno ozadnja procesov Standardnega modela, ki tvori pare enako nabitih leptonov, sem izpeljal metode, ki temeljijo na podatkih (ang. data-driven). Te metode so uporabljene do transverzalne gibalne količine leptonov vse do pT ~ 1 TeV. Rezultate smo interpretirali v okviru teorije levo-desne simetrije (ang. Left-Right Symmetry Model), specifično z iskanjem Higgsovega bozona z nabojem $\pm2$ ($H^{\pm\pm}$), težkih nevtrinov ($N_{\mathrm{R}}$) in težkih umeritvenih vektorskih bozonov ($W_{\mathrm{R}}$). S statistično obdelavo podatkov nismo opazili nobene sledi novih delcev. Posledično smo izpeljali spodnjo mejo za sipalni presek nastanka para bozonov $H^{\pm\pm}$ ($pp \to H^{++} H^{--}$) in za sipalni presek Keung-Senjanovi\'cevega procesa ($pp \to \ell N_{\mathrm{R}} \to \ell \ell W_{\mathrm{R}} \to \ell \ell j j$). Izpeljane spodnje meje so najstrožje do sedaj, poleg tega pa je predstavljena še nova metoda za karakterizacijo verjetnosti, da je naboj elektrona narobe rekonstruiran, ki je bila prvič uporabljena za analizo ATLAS-ovih podatkov v tem doktorskem delu.
Secondary keywords: fizika osnovnih delcev;eksperimentalna fizika delcev;detektor ATLAS;trki protonov;nova fizika;Higgsov bozon;istoznačni leptoni;
Type (COBISS): Doctoral dissertation
Study programme: 0
Thesis comment: Univ. v Ljubljani, Fak. za matematiko in fiziko, Oddelek za fiziko
Pages: XVIII, 258 str.
ID: 11008318