Searching for Squarks: in Compressed States and States with Jets from Charm Quarks with the Atlas Detector

This thesis explores searches for squarks in compressed scenarios where the scalar top is close in mass to the lightest supersymmetric particle. Two main analyses are presented: a search for scalar tops decaying to charm quarks and the development of a novel technique for reconstructing low momentum b-hadrons. These tools have enabled the ATLAS collaboration to explore topologies that were previously inaccessible.

Format: Paperback / softback
Length: 223 pages
Publication date: 28 August 2021
Publisher: Springer Nature Switzerland AG

This thesis delves into comprehensive searches for squarks utilizing the ATLAS detector in compressed scenarios where the scalar top, a close relative in mass to the lightest supersymmetric particle, assumes a significant role. These models hold theoretical allure as the presence of a quasi-degenerate scalar top enhances the self-annihilation cross-section of the lightest supersymmetric particle, thereby acting as a regulator of the dark matter relic density. Two primary analyses are presented. The first analysis focuses on the search for scalar tops decaying into charm quarks, a task that presents considerable challenges due to the short lifetime of charm quarks. The development of calibration tools for charm-tagging has paved the way for measuring the decay of the Higgs boson into pairs of charm quarks. The second analysis revolves around the development of a novel technique for reconstructing low-momentum b-hadrons. This innovative tool has opened up new avenues for exploration by the ATLAS collaboration, enabling them to delve into topologies that were previously inaccessible.

Introduction:
The study of squarks, fundamental particles in the Standard Model of particle physics, has garnered significant attention in recent years. Squarks are believed to play a crucial role in the formation of matter and the evolution of the universe. In this thesis, we focus on searches for squarks with the ATLAS detector in compressed scenarios where the scalar top, a close relative in mass to the lightest supersymmetric particle, assumes a significant role. These models hold theoretical allure as the presence of a quasi-degenerate scalar top enhances the self-annihilation cross-section of the lightest supersymmetric particle, thereby acting as a regulator of the dark matter relic density.

Two Main Analyses:
The first analysis presented in this thesis is a search for scalar tops decaying into charm quarks. The identification of jets originating from the charm quark is a challenging task due to its short lifetime. However, the calibration of tools for charm-tagging has paved the way for measuring the decay of the Higgs boson into pairs of charm quarks. This measurement provides crucial insights into the nature of the Higgs boson and the underlying physics of the universe.

The second analysis presented is the development of a novel technique for reconstructing low-momentum b-hadrons. This tool has enabled the ATLAS collaboration to explore topologies that were previously inaccessible. By reconstructing low-momentum b-hadrons, the ATLAS collaboration can gain a deeper understanding of the structure and properties of matter at the fundamental level.

Conclusion:
In conclusion, this thesis explores comprehensive searches for squarks with the ATLAS detector in compressed scenarios where the scalar top plays a significant role. The two main analyses presented provide valuable insights into the nature of squarks and the underlying physics of the universe. The development of calibration tools for charm-tagging and the development of a novel technique for reconstructing low-momentum b-hadrons have opened up new avenues for exploration by the ATLAS collaboration. The ongoing research in this field holds the potential to shed light on the mysteries of the cosmos and to deepen our understanding of the fundamental building blocks of nature.

Weight: 379g
Dimension: 235 x 155 (mm)
ISBN-13: 9783030542900
Edition number: 1st ed. 2020