Ortiz Parra, Lina Maria
(2021)
The effective field theory as a searching tool for presence of new physics in tt production with CMS.
[Laurea magistrale], Università di Bologna, Corso di Studio in
Physics [LMDM270]
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Abstract
Despite its success, the standard model (SM) presents some important shortcomings,
and because of these there has been a long search for physics beyond the SM which can
be associated to the production of new particles. Since for the moment there is no clear
evidence of this we are motivated to use effective field theory to characterise corrections
of the Lagrangian of the SM.
The CMS experiment uses the effective field theory (EFT) with four different approaches,
based on: 1) the reinterpretation of inclusive measurement, constraining the Wilson
coefficients by using EFT parametrizations; 2) relying on reinterpretation of differential
measurements at particle and parton level; 3) hybrid EFT measurements at detector
level; 4) by characterising EFT directly with the data.
Measurements of top quark tt differential crosssections using simulated events produced
in protonproton collisions are presented. The differential crosssection is defined as a
function of kinematic variables for the three decay channels: allhadronic, semileptonic
and dileptonic at particle and detector level. The crosssection has been measured for
the SM events and EFT using the ctG, cQq81 and ctq8 Wilson coefficients, which were
the most relevant. We analyse the different effects that are presented in each channel and
also which are the relevant kinematic variables in each case. Based on the differential
crosssection histograms we calculate the ratio between EFT and SM production, and
analyse the trend of the linear fit in order to see which variables could help us constrain
more the Wilson coefficients.
Abstract
Despite its success, the standard model (SM) presents some important shortcomings,
and because of these there has been a long search for physics beyond the SM which can
be associated to the production of new particles. Since for the moment there is no clear
evidence of this we are motivated to use effective field theory to characterise corrections
of the Lagrangian of the SM.
The CMS experiment uses the effective field theory (EFT) with four different approaches,
based on: 1) the reinterpretation of inclusive measurement, constraining the Wilson
coefficients by using EFT parametrizations; 2) relying on reinterpretation of differential
measurements at particle and parton level; 3) hybrid EFT measurements at detector
level; 4) by characterising EFT directly with the data.
Measurements of top quark tt differential crosssections using simulated events produced
in protonproton collisions are presented. The differential crosssection is defined as a
function of kinematic variables for the three decay channels: allhadronic, semileptonic
and dileptonic at particle and detector level. The crosssection has been measured for
the SM events and EFT using the ctG, cQq81 and ctq8 Wilson coefficients, which were
the most relevant. We analyse the different effects that are presented in each channel and
also which are the relevant kinematic variables in each case. Based on the differential
crosssection histograms we calculate the ratio between EFT and SM production, and
analyse the trend of the linear fit in order to see which variables could help us constrain
more the Wilson coefficients.
Tipologia del documento
Tesi di laurea
(Laurea magistrale)
Autore della tesi
Ortiz Parra, Lina Maria
Relatore della tesi
Scuola
Corso di studio
Indirizzo
NUCLEAR AND SUBNUCLEAR PHYSICS
Ordinamento Cds
DM270
Parole chiave
Effective field theory,standard model,top quarks,CMS,SMEFT,new physiscs,Wilson coefficients,crosssection
Data di discussione della Tesi
19 Febbraio 2021
URI
Altri metadati
Tipologia del documento
Tesi di laurea
(NON SPECIFICATO)
Autore della tesi
Ortiz Parra, Lina Maria
Relatore della tesi
Scuola
Corso di studio
Indirizzo
NUCLEAR AND SUBNUCLEAR PHYSICS
Ordinamento Cds
DM270
Parole chiave
Effective field theory,standard model,top quarks,CMS,SMEFT,new physiscs,Wilson coefficients,crosssection
Data di discussione della Tesi
19 Febbraio 2021
URI
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