Search for direct production of top quark pairs at sqrt(s) = 8 Tev using topological variables

When though the Standard Model (SM) has had a great success in the physical description of particles and its interactions, given the fact that all experimental measurements agree with its predictions, there are many well-founded reasons to believe that it is not a complete theory. Among these are the hierarchy problem as well as gravitation and dark matter which are not explained by the SM. Supersymmetry (SUSY) is an extension of the SM that could provide natural solution to the hierarchy problem: the cancellation of the quadratic divergences on the Higgs bosom mass (coming from the top quark loops) is achieved through the contribution of new loops from the supersymmetric particles. Furthermore, another strength of SUSY is that, if R-parity is satisfied in nature, the LSP (lightest SUSY particle) could be a good candidate from dark matter. The search for top quarks (stops) with masses below 1 TeV is motivated by many Super-symmetric models that provide a natural solution to the hierarchy problem of the Standard Model. Searches for direct production of pairs of stops at sqrt(s) = 8 TeV have been already performed by ATLAS and CMS experiments using cut & count and multivariate analysis techniques, based on kinematic variables to maximize the signal of background ratio. We report here the results of a search for direct production of stop pairs with the subsequent decay of each stop to a top quark and a neutralino, assuming a branching ratio of 100%, based on topological variables not used in previous analysis. We focus our search on the semileptonic channel of the top quark pairs produced, having as final state one single isolated lepton, more than three jets (at least one tagged as b-jet) and missing transverse energy

• Autores: Gómez Cardona, Juan Pablo
• Tipo de recurso: Doctoral thesis
• Fecha de publicación: 2015
• Institución: Universidad de los Andes
• Repositorio: Séneca: repositorio Uniandes
• Idioma: eng
• OAI Identifier: oai:repositorio.uniandes.edu.co:1992/7667
• Acceso en línea: http://hdl.handle.net/1992/7667
• Palabra clave: Supersimetría - Investigaciones; Partículas (Física nuclear) - Investigaciones; Quarks - Investigaciones; Leptones (Física nuclear) - Investigaciones; Física
• Rights: openAccess
• License: http://creativecommons.org/licenses/by-nc-sa/4.0/