| 1. |
- Aad, G, et al.
(författare)
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Search for dark matter in events with missing transverse momentum and a Higgs boson decaying into two photons in pp collisions at √s = 13 TeV with the ATLAS detector
- 2021
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Ingår i: Journal of High Energy Physics. - : Springer. - 1029-8479 .- 1126-6708. ; 2021:10
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Tidskriftsartikel (refereegranskat)abstract
- A search for dark-matter particles in events with large missing transverse momentum and a Higgs boson candidate decaying into two photons is reported. The search uses 139 fb−1 of proton-proton collision data collected at s = 13 TeV with the ATLAS detector at the CERN LHC between 2015 and 2018. No significant excess of events over the Standard Model predictions is observed. The results are interpreted by extracting limits on three simplified models that include either vector or pseudoscalar mediators and predict a final state with a pair of dark-matter candidates and a Higgs boson decaying into two photons.
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| 2. |
- Andrean, Stefio Yosse, 1991-
(författare)
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Search for New Scalar Particles with ATLAS
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Large Hadron Collider (LHC) is currently the most powerful particle accelerator ever built. It accelerates protons and collides them at the center of mass energy of √s = 13 TeV. At one of the collision points of LHC, a general-purpose particle detector — ATLAS — is installed to measure the outgoing particles produced in the collisions allowing the study of interactions between the elementary particles. The work presented in this thesis uses the collisions data produced by LHC and the data collected by ATLAS during the period of 2015-2018 which amounts to the integrated luminosity of 139 fb-1.This thesis focuses on searches of spin-0 particles in two areas of Beyond Standard Model physics: supersymmetry and extended Higgs sector. Supersymmetry offers a solution to the hierarchy problem by introducing partners to every Standard Model particle. Stop — the superpartner of the top quark — is particularly interesting due to its ability to cancel the dominant top contribution in the Higgs boson mass loop correction, and therefore becomes the target of a search in this thesis. Many Beyond Standard Model scenarios extend the Higgs sector for they are motivated by neutrino oscillations, dark matter, and baryogenesis. One of the consequences of these scenarios is the prediction of extra Higgs-like scalar particles which may decay into the 125 GeV Higgs boson. This is the signature targeted by the second ATLAS data analysis documented in this thesis.The thesis also includes a performance study of the Tile Calorimeter. The Tile Calorimeter is part of the ATLAS calorimeter system whose main task is to measure the energy of hadrons. The study is conducted on the Tile Calorimeter using muons from W boson decay originating from proton-proton collisions. Each calorimeter cell response is measured in data and compared with detector simulation to verify that the energy scale in simulation matches that in the real detector.
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| 3. |
- Andrean, Stefio Yosse, 1991-
(författare)
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Search for Stop Using the ATLAS Detector and Performance Analysis of the Tile Calorimeter with Muons from W Decays
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents a search for the supersymmetric partner of the top quark in the final state with one lepton. The search focuses especially in the region of the parameter space where the 2-body decay dominates. The analysis is performed using LHC full Run 2 data at √s = 13 TeV as recorded by the ATLAS detector. No significant excess above the backgrounds is observed, and 95% confidence level exclusion limits are calculated in the stop-neutralino mass plane. Stops are excluded up to 1200 GeV in the low neutralino mass scenario of below 400 GeV.The Tile Calorimeter is part of the ATLAS calorimeter system whose main task is to measure the energy of hadrons. A performance study is conducted on the Tile Calorimeter using muons from W boson decay originating from proton-proton collisions. Each calorimeter cell response is measure in data and compared with detector simulation. The azimuthal cell response uniformity is also investigated using a likelihood method. Overall, a good data to detector simulation agreement and azimuthal uniformity is observed which shows well-calibrated cells and uniform responses among the calorimeter modules.
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