Study of analytical methods for electron track detection from heavy quark decays generated by sqrt(s)=8TeV pp collisions at ALICE

• Ano de defesa: 2017
• Autor(a) principal: Luzio, Marco Aurelio
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: ALICE; Bethe-Bloch Equation; calorímetro eletromagnético; câmara de de projeção de tempo; CERN; colisão próton-próton; cortes de dados; Data Cuts; decaimento de sabores pesados; decaimento semileptônico; Electromagnetic Calorimeter; equação Bethe-Bloch; Heavy Flavor Decay; Semileptonic Decay; LHC; Proton-Proton Collision; tempo de voo; Time of Flight; Time Projection Chamber
• Link de acesso: http://www.teses.usp.br/teses/disponiveis/43/43134/tde-07062017-140205/

A study of the usage of ALICEs time of flight (TOF), time projection chamber (TPC), and electromagnetic calorimeter (EMCal), aiming at detecting and separating electrons and positrons (e±) originated from different sources, was carried out. To accomplish the objectives of the research, data gathered from the 2012 proton-proton (pp) collision experiment were used. At a center of mass energy of sqrt(s)=8TeV, the collision of the proton beams liberates heavy quarks, charm and bottom, with approximate lifetimes of approximately 10^13s and 10^12s, respectively. The e± generated through weak semileptonic heavy flavor decays are of interest for studying quarks, therefore it served solely as motivation and incentive for the research carried out and described herein. The introduction of carefully selected cuts, with the purpose of separating partial data collected in the three detectors, permitted the understanding of their effect on the results. Furthermore, due to the fact that the TOFs design was not meant to separate e± from the other heavier particles, only the general effects of introducing a simple cut in the beta=v/c values were analyzed. The more specific cuts were only used for the data generated by the events detected by the TPC and the EMCal. A combination of cuts based on the particles energy loss as a function of traveled distance (dE/dx), with the ratio of energy to momentum (E/p) of the particle, was adopted to enable the separation process, thus allowing for the isolation of e± from the other particles, namely pi±, K±, and p/p. The analysis was performed for values of total particle momentum in the range 0<=p<=6GeV/c. A comparison of the raw data with the results obtained by applying this procedure, indicated a substantial increase in the e± yield and efficiency, reaching average values above 90% over the entire momentum range.