Publication Date


Document Type


First Advisor

Chakraborty, Dhiman

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Physics


Nuclear physics


This dissertation describes a search for charged Higgs bosons decaying to a tau and a neutrino (H⁺ [right arrow] [tau]⁺[nu][sub t] or the charge-conjugate process) in association with a leptonically decaying top quark, using 36.1 fb⁻¹ of pp collision data collected with [square root]s = 13 TeV by the ATLAS detector. The theoretical motivation, including a review of the Standard Model, is given, along with a description of the ATLAS detector and particle reconstruction. A multi-variate analysis approach uses stochastic gradient boosted decision trees to improve the separation between H^[+/-] signal and background. The semi-leptonic channel described in this thesis is used in combination with a fully hadronic channel to search for charged Higgs bosons in a mass range of 90 GeV [less than or equal to] m[sub H^[+/-]] [less than or equal to] 2000 GeV. Finding no significant excess, limits are set at the 95% confidence level on the charged Higgs production cross section times the branching fraction into [tau][nu] ranging from 4.2 pb to 2.5 fb. These limits are interpreted in the hMSSM benchmark scenario as an exclusion at 95% confidence on tan[beta] as a function of m[sub H^[+/-]]. In this scenario, for tan[beta] = 60, the H^[+/-] mass range up to 1100 GeV is excluded, with all values of tan[beta] exclude for m[sub H^[+/-]] [precedes or equivalent to] 160 GeV.


Advisor: Chakraborty, Dhiman.||Committee members: Adelman, Jahred; Martin, Stephen.||Includes illustrations.||Includes bibliographical references.


105 pages




Northern Illinois University

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