Search for supersymmetry (SUSY) with topological variables at the LHC

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Fizik Bölümü, Türkiye

Tezin Onay Tarihi: 2015

Öğrenci: MESUT ÜNAL

Danışman: MEHMET TEVFİK ZEYREK

Özet:

The primary purpose of this thesis is to compare the effects on signal significance of the topological variables, W-stransverse mass ($M^W_{T2}$) and topness, which would be used in Supersymmetry searches in the single lepton channels in the future collider experiments. In this thesis, Stau-coannihilation scenarios were used as signal samples along with the four major background events, $t\bar{t}$+jets, boson+jets, single top+jets, and diboson, of supersymmetric top squark pair production and cascade decays. These brand new topological variables were proposed as an alternative to the classical variables such as $M_T$ and $H_T$ for background elimination due to the mathematically underconstrained nature of both $t\bar{t}$ and signal cascade decays. Since both the signal and the background samples were required to be produced at higher energies than the experiments conducted up to now, simulation programs such as Pythia and Delphes, were used to produce those samples. With the help of pyROOT data analysis framework, the samples are processed according to the kinematical and topological requirements. The results show that by applying a cut on both $M^W_{T2}$ and topness variables separately, a significant increase in the statistical significance of the signal was obtained. Moreover, these variables almost gave the same significance results for all the signal scenarios with or without pile-up.