Capozi, Matteo (2020): Precision calculations in the Higgs sector within and beyond the Standard Model. Dissertation, LMU München: Faculty of Physics 

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Abstract
The discovery of a boson consistent with the Standard Model (SM) Higgs boson in 2012 at the Large Hadron Collider (LHC) finally closed the hunting for the last unob served SM particle and experimentally confirmed the electroweak symmetry breaking mechanism. Nevertheless there are still open questions suggesting extensions of the SM. At the moment there is no evidence contradicting the SM and proving the pres ence of New Physics. New Particles could likely show up in the TeV range, if it is the case a good choice is to parametrise the Beyond Standard Model (BSM) effects in an Effective Field Theory framework. The New Physics effects are encoded in anomalous couplings. At the moment the Higgs sector is least explored and allows deviations from SM predictions, giving hints to extend this sector. We present the study of two processes of particular interest at the LHC: Higgs boson pair production and Higgs plus one jet production. In both cases we present the next toleading order (NLO) QCD cross section and differential distributions with full top mass dependence within the framework of a nonlinearly realised Effective Field Theory in the Higgs sector. In these calculations we explore the anomalous couplings parameter space probing the effects of these parameters on the observables. Concerning the Higgs boson pair production in the gluon fusion channel, character ized by five anomalous couplings, we present a calculation of the NLO QCD corrections where we analyse the impact of modifications of the anomalous couplings on the distri butions in the Higgs boson pair invariant mass and the transverse momentum of one of the Higgs bosons. We provide an analytical parametrisation for the total crosssection and the mhh distribution as a function of the anomalous Higgs couplings that includes NLO corrections. We further present our shapes classification of Higgs boson pair invariant mass dis tributions mhh. We use two approaches: an analysis based on predefined shape types and a classification into shape clusters based on unsupervised learning. We find that our method based on unsupervised learning allows a more detailed study of the impact of anomalous couplings on the mhh shape compared to more conventional approaches to a shape analysis. Higgs jet. At last we present the calculation of NLO QCD corrections for the Higgs plus one jet production. The computation is implemented in a Monte Carlo event generator code which will be publicly available. The scattering amplitude of the process is function of two anomalous couplings. Certain configurations of the couplings produce total cross sections which are almost the same. We study two of these configurations, and we show how to disentangle them.
Item Type:  Theses (Dissertation, LMU Munich) 

Subjects:  500 Natural sciences and mathematics 500 Natural sciences and mathematics > 530 Physics 
Faculties:  Faculty of Physics 
Language:  English 
Date of oral examination:  20. March 2020 
1. Referee:  Buchalla, Gerhard 
MD5 Checksum of the PDFfile:  df64234cd398ea53bcec93f214d889be 
Signature of the printed copy:  0001/UMC 27534 
ID Code:  26826 
Deposited On:  24. Nov 2020 10:52 
Last Modified:  30. Nov 2020 13:08 