Measurement of the differential cross section of the production Z boson decaying into electron-positron pairs in the ATLAS experiment

The first measurement of the phi_eta spectrum of Z bosons at 7 TeV of pp collisions has been studied in this thesis, which is an alternative way to probe the transverse momentum of Z bosons. The full data sample recorded by the ATLAS detector during 2011 run of the LHC was used, which corresponds with 4.7/fb integrated luminosity. The results of this measurement were reported in Ref. [18] supported by the internal note in Ref. [69]. The differential cross section of Z->ee as a function of phi_eta has been measured and compared to fixed order perturbative QCD calculations with/without a resummation for the low phi_eta region. Calculations using RESBOS provide the best descriptions of the data. However, they are unable to reproduce the detailed shape of the measured cross section to better than 4%. The differential cross section was also compared to predictions from different Monte Carlo generators interfaced to a parton shower algorithm. The best descriptions of the measured phi_eta spectrum are provided by SHERPA and POWHEG+PYTHIA8 Monte Carlo event generators. The precise measurement of the differential cross section as a function of phi_eta provides valuable information for the tuning of MC generators. The typical experimental precision of this measurement (~0.5%) is ten times better than the typical theoretical precision and therefore is valuable to constrain the theoretical predictions further. The ptZ measurement has been also studied to quantify the systematic uncertainty of this measurement using the high statistic data sample. This allows to compare two measurements which both address the physics issues of the Z transverse momentum. In most of the phi_eta range, the systematic uncertainty of the ptZ measurement is two times larger than the one of the phi_eta measurement. This comparison confirms the interest for the phi_eta variable. The measurements presented in this thesis has many implications for future studies. Tuning MC generators using the result of the precise measurement of the phi_eta spectrum will minimize the uncertainty on the tuned parameters. A double differential cross section measurement as a function of ptZ and phi_eta is interesting to understand the correlation between ptZ and phi_eta variables. The precise measurement of the ptZ spectrum using the new variable phi_eta can be applied to ptZ. More precise measurement of ptZ are important to obtain precise measurements of the W mass. In addition, a precise understanding of the ptZ spectrum is important to understand kinematic properties of Higgs boson production.

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Source https://theses.hal.science/tel-00846877
Author Doan, Thi Kieu Oanh
Maintainer CCSD
Last Updated May 10, 2026, 06:45 (UTC)
Created May 10, 2026, 06:45 (UTC)
Identifier NNT: 2012GRENY088
Language fr
Rights https://about.hal.science/hal-authorisation-v1/
contributor Laboratoire d'Annecy de Physique des Particules (LAPP) ; Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)
creator Doan, Thi Kieu Oanh
date 2012-11-28T00:00:00
harvest_object_id f908bd5e-ef9a-44c8-9237-8653ecb203de
harvest_source_id 3374d638-d20b-4672-ba96-a23232d55657
harvest_source_title test moissonnage SELUNE
metadata_modified 2026-03-31T00:00:00
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