“Precisión en producción de Higgs en el LHC”
2020
Tesista | Ignacio FABRE Magister en Ciencias Físicas, Univ. Nac. Cuyo, Inst. Balseiro Doctor en Ciencia y Tecnología, Mención Física, Instituto Sabato UNSAM/CNEA - Argentina |
Directores | Dr. Daniel de Florian, UNSAM, CONICET, UBA - Argentina Dr. Massimiliano Grazzini, Universidad de Zúrich - Suiza |
Lugar de realización | ICAS (International Center for Advanced Studies) de la Universidad Nacional de San Martín. |
Fecha Defensa | 28/08/2020 |
Jurado | Dr. Leandro DA ROLD. CONICET, CNEA, UNCu - Argentina Prof Dr. Rodolfo SASSOT. CONICET, UBA - Argentina. Prof. Dr. Thomas GEHRMANN. UZH - Suiza. Prof. Dr. Stefano POZZORINI. UZH - Suiza. Dr. Ezequiel ALVAREZ. CONICET, UNSAM -Argentina. |
Código | ITS/TD-139/20, |
Título completo
“Precisión en producción de Higgs en el LHC”
Resumen
Complete Title
“Precision in Higgs production at the LHC”
Abstract
About ten years after the start of the LHC the results obtained by the ATLAS and CMS collaborations have not shown evidence of physics beyond the Standard Model (BSM). As the experimental efforts to find BSM physics move from resonant searches to precision measurements, accurate theory predictions are needed. Particular interest lies in the Higgs boson self couplings, as they are directly connected to the scalar potential that drives ElectroWeak Symmetry Breaking. An important role in this context is played by the top quark, which is the heaviest known fundamental particle and the one with the largest coupling with the Higgs boson. The value of the top Yukawa coupling drives the evolution of the Higgs boson self coupling, and has a great impact in the Higgs boson production cross section at hadronic colliders, where the main production channel is gluon fusion mediated by a top-quark loop. The most direct way to access the Higgs boson self couplings is through multiple Higgs boson production. In the first part of this thesis, we will compute the Next-to-Next-to-Leading Order QCD corrections to its production cross section in the heavy-top approximation. In the case of double Higgs production, we will extend the known NNLO results to the SM cross section to include new physics effects, which are parametrised by six-dimensional operators in the context of the standard model effective field theory. This is a way to consistently parametrise heavy new physics, while being agnostic to the UV complete theory that underlies it. In the case of triple Higgs production, we will compute the NNLO QCD corrections to the SM process in the heavy-top limit, and combine it with the current best approximation to the top-quark mass effects, thus obtaining our best prediction for its cross section. Unlike other quarks, the decay of a Higgs boson into a pair of top-quarks is kinematically forbidden, but a direct observation of the top-quark Yukawa coupling is possible in the associated production of a top quark pair and a Higgs boson. In a context in which the experimental accuracy is getting closer to the current theory uncertainty, we need a framework to compute the NNLO QCD corrections to this process. In the second part of this thesis we will extend the qT-subtraction framework, which currently has been implemented for colourless and t ̄t final states, to the t ̄th process. We will present a full implementation for the NLO cross section and for the NNLO counter-terms, needed to regulate the divergences appearing in the real emission cross sections. These results pave the way to the full computation of NNLO QCD corrections to t ̄th hadroproduction.
volver al listado