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Search for new physics processes with same sign leptons in the final state with the ATLAS detector
ID Muškinja, Miha (Author), ID Kerševan, Borut Paul (Mentor) More about this mentor... This link opens in a new window, ID Gorišek, Andrej (Co-mentor)

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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.

Language:English
Keywords:ATLAS, same-charge leptons, seesaw model, Higgs: charge 2, neutrino: right-handed, CERN LHC, two jets, left-right symmetry, Higgs: pair production, neutrino: heavy, 13 TeV
Work type:Doctoral dissertation
Typology:2.08 - Doctoral Dissertation
Organization:FMF - Faculty of Mathematics and Physics
Year:2018
PID:20.500.12556/RUL-106111 This link opens in a new window
COBISS.SI-ID:3240036 This link opens in a new window
Publication date in RUL:28.01.2019
Views:1168
Downloads:298
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Secondary language

Language:Slovenian
Title:Iskanje procesov nove fizike s pari enako nabitih leptonov v končnem stanju z detektorjem ATLAS
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.

Keywords:ATLAS, istoznačni leptoni, gugalnični model, Higgs: naboj 2, desno-ročni nevtrino, CERN LHC, dva pljuska, levo-desna simetrija, Higgs: nastanek v paru, težki nevtrino, 13 TeV, visoka masa leptonov, skalarni triplet, Higgs: razpad na leptone, Majoranov nev

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