Enhancing Low Mass Dark Matter Mediator Resonance Searches with Improved Triggering in the ATLAS Detector PDF Download

Author: Claire Antel
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Eric Edward Corrigan
Publisher:
ISBN: 9789178959112
Category :
Languages : en
Pages :

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Dark matter is abundant in the universe, yet its composition and nature are unknown. If dark matter consists of new particles with nonzero interactions with Standard Model particles, it could be produced and detected or inferred by collider experiments. This thesis describes searches for dark matter models with new spin-1 force mediators coupling dark matter to quarks, using the ATLAS detector at the LHC. The studies target processes where a mediator is resonantly produced and decays back into two quarks, leaving two collimated jets of particles in the detector, and use $\sqrt{s} = 13 \TeV$ data recorded by ATLAS between 2015 and 2017. No evidence for new physics was seen, and exclusion limits were set on benchmark models. Additionally, we describe how such limits can be reinterpreted in the contexts of other models to provide further constraints. In order to conduct these searches, well-calibrated jets are needed, as well as good understanding of detector performance. This thesis also describes several tools and studies aimed at improving the jet physics performance of ATLAS. In particular, methods for studying the jet energy calibration and resolution are presented.

Author: Steven Schramm
Publisher: Springer
ISBN: 3319444530
Category : Science
Languages : en
Pages : 341

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This thesis describes the search for Dark Matter at the LHC in the mono-jet plus missing transverse momentum final state, using the full dataset recorded in 2012 by the ATLAS Experiment. It is the first time that the number of jets is not explicitly restricted to one or two, thus increasing the sensitivity to new signals. Instead, a balance between the most energetic jet and the missing transverse momentum is required, thus selecting mono-jet-like final states. Collider searches for Dark Matter have typically used signal models employing effective field theories (EFTs), even when comparing to results from direct and indirect detection experiments, where the difference in energy scale renders many such comparisons invalid. The thesis features the first robust and comprehensive treatment of the validity of EFTs in collider searches, and provides a means by which the different classifications of Dark Matter experiments can be compared on a sound and fair basis.

Author: Ruth Pöttgen
Publisher: Springer
ISBN: 3319410458
Category : Science
Languages : en
Pages : 325

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This thesis describes in detail a search for weakly interacting massive particles as possible dark matter candidates, making use of so-called mono-jet events. It includes a detailed description of the run-1 system, important operational challenges, and the upgrade for run-2. The nature of dark matter, which accounts for roughly 25% of the energy-matter content of the universe, is one of the biggest open questions in fundamental science. The analysis is based on the full set of proton-proton collisions collected by the ATLAS experiment at the Large Hadron Collider at √s = 8 TeV. Special attention is given to the experimental challenges and analysis techniques, as well as the overall scientific context beyond particle physics. The results complement those of non-collider experiments and yield some of the strongest exclusion bounds on parameters of dark matter models by the end of the Large Hadron Collider run-1. Details of the upgrade of the ATLAS Central Trigger for run-2 are also included.

Author: Caterina M. L. Marcon
Publisher:
ISBN: 9789178958849
Category :
Languages : en
Pages :

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Elementary particles and their interactions are successfully described by the Standard Model of particle physics (SM). However, it has been observed that extensions Beyond the Standard Model (BSM) are required to account for a large part of yet undiscovered particles and interactions, such as Dark Matter (DM). To advance the knowledge of the SM and to pursue DM discoveries, CERN has the ambitious plan of further increasing the Large Hadron Collider's (LHC) energy and luminosity, thus reaching unprecedented event rates in the field of collider physics. This thesis is divided in three parts, dealing with some of the most challenging aspects of the ATLAS experiment at the LHC present and future activities. After a thorough review of the SM, BSM physics is outlined, with particular attention to DM searches. The second part of this work addresses the issue of coping with the foreseen event rates of the High-Luminosity LHC (HL-LHC) phase. Indeed, optimizations of the existing Geant4 simulation codes are a crucial step to alleviate the need for new and expensive hardware resources. With the objective of improving the efficiency of the simulation tools, an extensive study on different compilers, different optimization levels and different build types is presented. In addition, a preliminary investigation on the geometry description of the ATLAS Transition Radiation Tracker (TRT) modules is discussed. The last part of the thesis covers the DM searches carried out by the ATLAS Trigger-object Level Analysis (TLA) group. These searches are based on the analysis of the invariant mass spectrum of di-jet events and, during LHC Run 2, have been performed at energies in the 450-1800 GeV range (integrated luminosity up to 29.3 fb-1 and center of mass energy of 13 TeV). After a review of the TLA studies, a preliminary investigation on the performance of Bayesian and Frequentist statistical tools is presented. In particular, the attention is focused on the interpretation and handling of systematic uncertainties both on background and DM signals. This is of particular importance in the process of finding localized excesses, which can indicate the existence of DM signals, and setting limits on the DM event cross sections.

Author: Manuel Patrice Geisler
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: [Study Group] ATLAS Collaboration CERN
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Abstract: Results from a wide range of searches targeting different experimental signatures with and without missing transverse momentum (EmissT) are used to constrain a Two-Higgs-Doublet Model (2HDM) with an additional pseudo-scalar mediating the interaction between ordinary and dark matter (2HDM+a). The analyses use up to 139 fb−1 of proton-proton collision data at a centre-of-mass energy s√=13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015-2018. The results from three of the most sensitive searches are combined statistically. These searches target signatures with large EmissT and a leptonically decaying Z boson; large EmissT and a Higgs boson decaying to bottom quarks; and production of charged Higgs bosons in final states with top and bottom quarks, respectively. Constraints are derived for several common as well as new benchmark scenarios within the 2HDM+a

Author: Yangyang Cheng
Publisher: Springer
ISBN: 331944218X
Category : Science
Languages : en
Pages : 183

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This thesis reports on the search for dark matter in data taken with the ATLAS detector at CERN’s Large Hadron Collider (LHC). The identification of dark matter and the determination of its properties are among the highest priorities in elementary particle physics and cosmology. The most likely candidate, a weakly interacting massive particle, could be produced in the high energy proton-proton collisions at the LHC. The analysis presented here is unique in looking for dark matter produced together with a Higgs boson that decays into its dominant decay mode, a pair of b quarks. If dark matter were seen in this mode, we would learn directly about the production mechanism because of the presence of the Higgs boson. This thesis develops the search technique and presents the most stringent production limit to date.

Author:
Publisher:
ISBN:
Category :
Languages : en
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This article reports on a search for dark matter pair production in association with bottom or top quarks in 20.3 fb-1 of pp collisions collected at √s = 8 TeV by the ATLAS detector at the LHC. Events with large missing transverse momentum are selected when produced in association with high-momentum jets of which one or more are identified as jets containing b-quarks. Final states with top quarks are selected by requiring a high jet multiplicity and in some cases a single lepton. The data are found to be consistent with the Standard Model expectations and limits are set on the mass scale of effective field theories that describe scalar and tensor interactions between dark matter and Standard Model particles. Limits on the dark-matter-nucleon cross-section for spin-independent and spin-dependent interactions are also provided. These limits are particularly strong for low-mass dark matter. Using a simplified model, constraints are set on the mass of dark matter and of a colored mediator suitable to explain a possible signal of annihilating dark matter.

Author: Eugenio Del Nobile
Publisher: Springer Nature
ISBN: 3030952282
Category : Science
Languages : en
Pages : 261

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This book is a pedagogical guide on how to make computations in direct dark matter (DM) detection. The theory behind the calculation of direct detection cross sections and rates is presented, touching aspects related to elementary particle physics, hadronic physics, nuclear physics, and astrophysics. The book is structured in self-contained sections, covering several topics ranging from the scattering kinematics to the phenomenology of direct DM searches. It follows a model-independent approach, aiming at providing the readers with all that is needed to understand the theory and start their own analysis. Meant for graduate students and researchers with interests in particle physics and phenomenology, it is enriched with several worked examples from standard and non-standard particle DM models. Senior researchers working in different areas related to dark matter, like particle and nuclear physics, astrophysics, and cosmology, find in this book a useful and updated guide for reference.