Measurements of Z→vv+jets to Z→ll+jets differential cross section ratios in pp collisions at √s = 13 TeV using the ATLAS Detector
Son, Hyungsuk.
2019
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This thesis presents measurements of the Z→vv+jets to Z→ll+jets
differential cross section ratios as a function of various observables using
proton-proton collisions at a center of mass energy of √s = 13 TeV. Since the
Z→vv+jets process is very similar to the Z→ll+jets process for QCD effects and jet
kinematics, many experimental and theoretical uncertainties on the modeling of the
SM events ... read morewill cancel in the ratio. Each of the measured ratios is unfolded to be
comparable to the corresponding theoretical predictions without the detector
effects. With these techniques, two analyses were carried out based on the data
collected by the ATLAS experiment and used to get the results presented in this
thesis. The first analysis consists of two measurements of the ratio of Zpt
distribution, a QED measurement and a measurement of the invisible width of the Z.
This analysis used the full 2015+2016 dataset with a total integrated luminosity
of 36.2 fb-1. Preliminary results for the QED measurement show that the QED FSR
modeling provides a fair description of electron data and excellent agreement with
data in the muon channel. The invisible width of the Z is also extracted using the
measured unfolded ratio. A precision comparable to LEP most precise results have
been obtained, improving the overall precision on the direct determination of this
parameter by about 40%. The purpose of the second analysis is to search for beyond
the Standard Model (BSM) physics. This analysis describes a measurement of
detector-corrected observables sensitive to the anomalous production of events
with jet and large missing transverse momentum in pp collisions using 3.2 fb-1 of
data collected in 2015. The measured ratios are found to be in agreement with the
Standard Model prediction and the data is used to place limits on various
theoretical models for dark matter production. The limits in simplified models are
competitive with detector-level approaches and provide improved sensitivity to
models in which the dark matter mass is close to half the mediator
mass.
Thesis (Ph.D.)--Tufts University, 2019.
Submitted to the Dept. of Physics.
Advisor: Pierre-Hugues Beauchemin.
Committee: Gary Goldstein, Krzysztof Sliwa, Cristian Staii, and Benjamin Brau.
Keywords: Particle physics, and Physics.read less - ID:
- ng451w122
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