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oai:ubir.buffalo.edu:10477/809312026-04-24T20:24:27Zcom_10477_77914col_10477_80447

Search for t¯t Resonances in Dilepton Channel at the CMS Data Using Polarization Information Kilcoyne, Bahareh; 0000-0002-0773-7182 Iashvili, Ia Physics particle physics Ph.D. A search for heavy t¯t resonances is performed using the Large HadronCollider’s proton-proton collisions data collected by the Compact MuonSolenoid detector during year 2016. The analysis is optimized for eventswhere highly boosted top and anti-top quarks decay in dileptonic channel.Various kinematic variables are studied to achieve sensitivity for thesignal detection. No significant excess of events relative to the expectedyield from the Standard Model processes is observed. Upper limits onthe production cross section of heavy resonances decaying to a t¯t pairare calculated. We exclude Kaluza–Klein excitations of the gluon in theRandall–Sundrum and leptophobic topcolor Z’ models. Expected 95%CL upper limits on the production cross section obtained to be between3 × 10−2 - 20 pb for the resonance masses of 0.5 TeV to 5 TeV.To probe the signal mass region above these exclusions poses a challengeas we enter in the limited parton luminosity range of the LHC collisionsthat leads to decreasing search sensitivity to the signal when relying onlyon high momentum transfer variables for signal/background discrimination.To improve the signal/background discrimination, we identify andstudy variables that allow to regain sensitivity to high mass resonancesin the dilepton channel. We show using the top quark polarizationinformation through angular and energy variables provides additionalhandle to discriminate against the dominant SM t¯t production. Wefurther combine the polarization variables and kinematic variables inmultivariate approach to enhance sensitivity to the signal, particularlyfor the heavy mass resonances. **To request an accessible version of the file(s) associated with this item, contact library@buffalo.edu. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.** 2019-10-29T16:48:15Z 2019-10-29T16:48:15Z 2019 2019-08-08 17:29:50 Text Dissertation http://hdl.handle.net/10477/80931 eng Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions. Copyright retained by author. application/pdf State University of New York at Buffalo