Browsing by Author "Kruse, Mark"
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Item Open Access A Measurement of the Production Cross Section of a Single Top Quark in Association with a $W$-boson at $\sqrt{s} = 13$ TeV with the ATLAS Detector at the Large Hadron Collider(2020) Davis, DouglasA measurement of the Standard Model cross section for the production of a single top quark in association with a $W$-boson from proton-proton collisions is presented. Collision data at a center-of-mass energy of 13 TeV totaling 139 inverse femtobarns collected by the ATLAS detector on the Large Hadron Collider is used to study the process. Binary classifiers trained using kinematic properties of observable particles are used to separate the signal process from a large top pair production background. A binned maximum likelihood fit is performed to extract the Standard Model cross section for the signal process, along with a secondary top pair cross section measurement and uncertainties related to object reconstruction with the detector and theoretical models. The measured cross section is the most precise measurement performed using the ATLAS detector and is in good agreement with the Standard Model prediction.
Item Open Access An Inclusive Analysis of Top Quark Pair, W Boson Pair, and Drell-Yan Tau Lepton Pair Production in the Dilepton Final State from Proton-Proton Collisions at Center-of-Mass Energy 7 TeV with the ATLAS Detector(2013) Finelli, KevinA simultaneous measurement of three Standard Model cross-sections using 4.7 inverse femtobarns of proton-proton collision data at a center-of-mass energy of 7 TeV is presented. Collision data were collected using the ATLAS detector at the Large Hadron Collider. The signal production cross-sections studied are for top quark pair production, charged weak boson pair production, and Drell-Yan production of tau lepton pairs with invariant mass greater than 40 GeV. A data sample is defined from events with isolated high-energy electron-muon pairs arranged in a phase space defined by missing transverse momentum and jet multiplicity. A binned maximum likelihood fit is employed to determine signal yields in this phase space. Signal event yields are in turn used to measure full cross-section values and cross-section values within a fiducial region of the detector, and unlike conventional measurements the signal measurements are performed simultaneously. This is the first such simultaneous measurement of these cross-sections using the ATLAS detector. Measured cross-sections are found in good agreement with the most precise published theoretical predictions.
Item Open Access Indication of electron neutrino appearance from an accelerator-produced off-axis muon neutrino beam.(2012) Albert, Joshua BenjaminT2K (Tokai to Kamioka) is a long baseline neutrino experiment with the primary goal of measuring the neutrino mixing angle 13. It uses a muon neutrino beam, produced at the J-PARC accelerator facility in Tokai, sent through a near detector complex on its way to the far detector, Super-Kamiokande. Appearance of electron neutrinos at the far detector due to oscillation is used to measure the value of 13. This dissertation describes the experimental setup, analysis methods, and results from the analysis of T2K data taken from January 2010 through March 2011. Six signal candidate events were observed on an expected background of 1:5 0:3. The probability to see six or more such events is 0.7% under the 13 = 0 hypothesis. This is the first experiment to exclude 13 = 0 at the 90% confidence level. The 90% confidence level allowed region is 0:03p0:04q sin2 2 13 0:28p0:34q with a best fit point of sin2 2 13 = 0:11p0:14q for CP = 0 and | m2 32| = 2:4 x 10-3 eV2 in the normal (inverted) hierarchy.Item Open Access Measurement of the tt̅W and tt̅Z Cross Sections using Proton-Proton Collisions at √s = 8 TeV with the ATLAS Detector(2016) Zhou, ChenA measurement of the production cross sections of top quark pairs in association with a W or Z boson is presented. The measurement uses 20.3 fb−1 of data from proton-proton collisions at √s = 8 TeV collected by the ATLAS detector at the Large Hadron Collider. Four different final states are considered: two opposite-sign leptons, two same-sign leptons, three leptons, and four leptons. The t t̅ W and t t̅ Z cross sections are simultaneously extracted using a maximum likelihood fit over all the final states. The t t̅ Z cross section is measured to be 176+58−52 fb, corresponding to a signal significance of 4.2σ. The t t̅ W cross section is measured to be 369+100−91 fb, corresponding to a signal significance of 5.0σ. The results are consistent with next-to-leading-order calculations for the tt̅W and tt̅Z processes.
Item Open Access Search for a Fermiophobic Beyond the Standard Model Charged Higgs boson through W γ resonances for masses below 200 GeV(2023) Patel, Utsav MukeshA search for a beyond the Standard Model charged Higgs boson through a combined $W\gamma$ resonance is presented. The final state consists of an electron or a muon accompanied by at least one photon. The search is uses 140 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 13 TeV collected using the ATLAS detector within the Large Hadron Collider. A binned maximum likelihood fit is performed with signal samples in the mass range of 110 to 200 GeV. The invariant mass of the $W\gamma$ system is used as a discriminant in the statistical analysis methods. In this analysis, we place exclusion limits on producing a fermiophobic charged Higgs decaying to a $W\gamma$ pair through focuses on model-dependent and model-independent approaches. Exclusion limits are also presented for producing a fermiophobic charged Higgs through a di-Higgs Drell-Yan process with the requirement of at least one charged Higgs producing a $W\gamma$ pair of particles in the final state. As such, we extend the exclusion limits to cover the mass range of Beyond the Standard Model Higgs of 110-200 GeV.
Item Open Access Search for new phenomena using three-photon final states in data collected with the ATLAS detector at the Large Hadron Collider(2021) Zhao, PingchuanThis thesis presents a search for new phenomena using three high-$p_T$ photons in the final state. In some Beyond the Standard Model (BSM) theories, a vector boson, $Z^\prime$, can decay to a pseudoscalar, $a$, and a photon, $\gamma$. The pseudoscalar can then decay into two photons: $Z^\prime \rightarrow a \gamma \rightarrow \gamma \gamma \, \gamma$. In addition, the Standard Model (SM) $Z$ boson can rarely decay into three photons via fermion and boson loops. The branching ratio for this decay is extremely small (order of $10^{-10}$) in the SM, and has not yet been observed, with the best limits for this branching ratio being of order $10^{-6}$. A secondary goal of this analysis is to search for $Z \rightarrow \gamma \gamma \gamma$ as a test of the SM, and if not observed to set a better limit on this branching ratio. The dataset used for this analysis was collected at the CERN Large Hadron Collider (LHC) during the run period from 2015 to 2018. The proton-proton collision center-of-mass energy was 13\,TeV and the corresponding integrated luminosity recorded by the ATLAS detector was $139\,{\rm fb^{-1}}$.
Item Open Access Search for top-philic heavy resonances using the single-lepton decay channel in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector(2024) Le Boulicaut Ennis, EliseA search for heavy resonances coupling exclusively to top quarks (top-philic) is presented. These resonances are predicted by extensions of the Standard Model of particle physics which, among other things, attempt to explain the Higgs boson mass in a ``natural'' way which does not require as much fine-tuning as is presently necessary. The analysis focuses on final states with three or four top quarks in the single lepton channel and makes use of $139~\textrm{fb}^{-1}$ of proton-proton collision data collected by the ATLAS detector between 2015 and 2018 at a center-of-mass energy of 13 TeV. No signs of new physics are observed and therefore limits are set on the production cross section of top-philic resonances with masses between 1 and 3 TeV. The observed (expected) limits range from 21 (14) fb to 119 (86) fb depending on the choice of model parameters.
Item Open Access Speculative Physics: the Ontology of Theory and Experiment in High Energy Particle Physics and Science Fiction(2014) Lee, Clarissa Ai LingThe dissertation brings together approaches across the fields of physics, critical theory, literary studies, philosophy of physics, sociology of science, and history of science to synthesize a hybrid approach for instigating more rigorous and intense cross-disciplinary interrogations between the sciences and the humanities. I explore the concept of speculation in particle physics and science fiction to examine emergent critical approaches for working in the two areas of literature and physics (the latter through critical science studies), but with the expectation of contributing new insights to media theory, critical code studies, and also the science studies of science fiction.
There are two levels of conversations going on in the dissertation; at the first level, the discussion is centered on a critical historiography and philosophical implications of the discovery Higgs boson in relation to its position at the intersection of old (current) and the potential for new possibilities in quantum physics; I then position my findings on the Higgs boson in connection to the double-slit experiment that represents foundational inquiries into quantum physics, to demonstrate the bridge between fundamental physics and high energy particle physics. The conceptualization of the variants of the double-slit experiment informs the aforementioned critical comparisons. At the second level of the conversation, theories are produced from a close study of the physics objects as speculative engine for new knowledge generation that are then reconceptualized and re-articulated for extrapolation into the speculative ontology of hard science fiction, particularly the hard science fiction written with the double intent of speaking to the science while producing imaginative and socially conscious science through the literary affordances of science fiction. The works of science fiction examined here demonstrate the tension between the internal values of physics in the practice of theory and experiment and questions on ethics, culture, and morality.
Nevertheless, the dissertation hopes to show the beginnings of a possibility, through the contentious but generative space provided by speculative physics, to produce more cross-collaborative thinking between physics as represented by the hard sciences, and science fiction representing the objects of literary enterprise and creative evolution.