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doctoral thesis

Electroweak and Higgs Physics at Very High Energy

Ricci, Lorenzo  
2022

Effective Field Theories (EFTs) allow a description of low energy effects of heavy new physics Beyond the Standard Model (BSM) in terms of higher dimensional operators among the SM fields. EFTs are not only an elegant and consistent way to describe heavy new physics but they represent, at the same time, a valuable experimental tool for collider searches. The Standard Model Effective Field Theory naturally parametrizes the space of models BSM and measuring its interactions is, nowadays, substantial part of the theoretical and the experimental program at the (HL-)LHC and at future colliders.

In this thesis we address the theoretical challenges of this Beyond the Standard Model precision program, following three different paths.

Firstly, we present some results towards the so-called high-$p_T$ program at the (HL-)LHC, targeting to measure energy growing effects of higher dimensional operators in the tail of kinematic distributions. Concretely, we focus on dilepton production and we study the sensitivity to flavor universal dimension-six operators interfering with the SM and enhanced by the energy. We produce theoretical predictions for the SM and the dim-6 EFT operators at NLO-QCD, including 1-loop EW logs. Our predictions are based on event reweighting of SM Montecarlo simulations and allow an easy scan of the multi-dimensional new physics parameter space on data. Furthermore we asses the impact of the various sources of theoretical uncertainties and we study the projected sensitivity of (HL-)LHC to the EFT interactions under consideration and to concrete BSM scenario.

We then turn to future colliders and in particular to very high energy lepton colliders. In this context we study the potential of such machines with about 10 TeV center of mass energy to probe Higgs, ElectroWeak and Top physics at 100 TeV via precise measurements of EFT interactions. A peculiar aspect of so energetic ElectroWeak processes is the prominent phenomenon of the EW radiation. On one hand we find that consistent and sufficiently accurate predictions require resummations, that we perform at double logarithmic order. On the other hand we show how the study of the radiation pattern can enhance the sensitivity to new physics. We assess our results in Composite Higgs and Top scenarios and minimal Z' models.

Finally, we move to a top-down perspective and we perform a phenomenological study of composite Higgs models with partially composite Standard Models quarks. Starting from maximally symmetric scenarios that realize minimal flavor violation, we test various assumptions for the flavor structure of the strong sector. Among the different models we consider, we find that there is an optimal amount of symmetries that protects from (chromo-)electric dipoles and reduces, at the same time, constraints from other flavor observables.

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Type
doctoral thesis
DOI
10.5075/epfl-thesis-10051
Author(s)
Ricci, Lorenzo  
Advisors
Wulzer, Andrea  
Jury

Prof. Laurent Villard (président) ; Dr Andrea Wulzer (directeur de thèse) ; Prof. Joao Penedones, Prof. Alex Pomarol, Prof. Paolo Nason (rapporteurs)

Date Issued

2022

Publisher

EPFL

Publisher place

Lausanne

Public defense year

2022-09-30

Thesis number

10051

Total of pages

224

Subjects

Effective Field Theories

•

Precision physics

•

Beyond the Standard Model

•

Flavor physics

•

Future Colliders

•

Collider physics

•

Composite Higgs

•

Partial compositeness

EPFL units
LPTP  
Faculty
SB  
School
IPHYS  
Doctoral School
EDPY  
Available on Infoscience
October 3, 2022
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/191148
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