University of Twente Student Theses


Constraining the standard model effective field theory Wilson coefficients using Higgs and diboson data

Kortman, Bryan (2019) Constraining the standard model effective field theory Wilson coefficients using Higgs and diboson data.

[img] PDF
Abstract:A measurement of several free parameters in the Standard Model Effective Field Theory (SMEFT)known as Wilson coefficients is carried out. The measurement is performed using data accumulated between 2015 and 2016 at the ATLAS detector. Proton-proton collisions were produced at Large Hadron Collider in CERN, Geneva, with a total integrated luminosity of 36.1 f b¡1 and a center-of-mass energy of p s Æ 13 TeV . The events are used to study Higgs production in gluon-gluon fusion (ggF) and vector boson fusion (VBF). The H ¡!WÅW¡ ¡!eº¹º decay channel is considered. A dataset from charged vector boson pair production through interactions of quarks and gluons qq/g g ¡!WÅW¡ ¡!eº¹º is also incorporated. Constraints on 17 CP-even operators were obtained using Effective LagrangianMorphing. Only contribution up to order 1/¤2 are taken into account. Operators affect the production and decay couplings in both ggF and VBF Higgs production, as well as the qq/g g ¡! WÅW¡ production. The contribution of these operators are estimated by linking deviations from the Standard Model(SM) in Simplified Template Cross Sections (STXS) to the effects of dimension-6 operators. The SM and interference Monte Carlo (MC) samples are generated at LO with MadGraph5 and Pythia8. The interference samples are obtained by only generating the LOinterference between the EFT and SM couplings. The dimensionality of the interpretation is greatly increased using this method. The MC samples are used in the interpolation technique effective Lagrangian morphing. The effective Lagrangian morphing uses the analytical structure of the Lagrangian to interpolate between different phase space regions allowing for theory predictions of kinematic distributions. This results in a continuous description of the kinematic observables as a function of the Wilson coefficients associated to the dimension-6 operators. A reparameterization of the ggF and VBF STXS regions is expressed in terms of the SMEFT Wilson coefficients. Profile Likelihood fits are performed on the reparameterized measurement. The fitting algorithm uses the reparameterized framework of the analyses to obtain constraints on theWilson coefficients. The analysis incorporates systematic and statistical uncertainties. Finally, the sensitivity of the EFT interpretation is improved by incorporating qq/g g ¡!WW data and the corresponding EFT interpretation. The final results show deviations of O(1¾) from the StandardModel prediction.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:33 physics
Programme:Applied Physics MSc (60436)
Link to this item:
Export this item as:BibTeX
HTML Citation
Reference Manager


Repository Staff Only: item control page