Investigation of the CP properties of VBF Higgs production in hadronic final states of H → τ τ decays with the ATLAS detector

Investigation of the CP properties of VBF Higgs production in hadronic final states of H → τ τ decays with the ATLAS detector

Serhat Ördek

Doctoral thesis

Date of Examination: 2021-01-28

Date of issue: 2021-02-15

Advisor: Lai, Stan Prof. Dr.

Referee: Lai, Stan Prof. Dr.

Referee: Quadt, Arnulf Prof. Dr.

Persistent Address: http://hdl.handle.net/21.11130/00-1735-0000-0005-156E-9

Files in this item

Name: oerdekDiss.pdf

Size: 6,3 MB

Format: PDF

View/Open

The following license files are associated with this item:

Creative Commons

Abstract

English

A test of CP invariance of the VBF Higgs production process is presented in the τ τ final state. For this, a profile likelihood fit using a matrix-element observable method is employed to test whether a CP-odd component is present in the coupling. The analysis is carried out using 36.1 fb −1 of proton-proton collision data recorded at a centre-of- mass energy of 13 TeV with the ATLAS detector at the LHC. It constrains the value of the CP violation inducing parameter d ̃ to [−0.090, 0.035] at the 68% confidence level. This result is compatible with the Standard Model expectation of d ̃ = 0 and no CP violation. Particular emphasis is put on the final state including two hadronically- decaying τ leptons. Additionally, a measurement of the efficiencies of τ -lepton triggers is presented. These triggers are necessary to collect the data on which the measurement of d ̃ is based. Lastly, an ongoing measurement of Higgs-boson production cross-sections in the τ τ final state using 139 fb −1 of data is discussed, including an improved method of estimating back- ground contributions in the final state with two hadronically-decaying τ leptons.

Keywords: Higgs boson; CP violation