Exploring the 95 GeV Excess with Extended Scalar Models

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2024-10

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University of the Witwatersrand, Johannesburg

Abstract

This thesis focuses on three interconnected studies investigating the presence of an additional scalar particle, S, of mass around mS ≈ 95 GeV. In the initial study, we explore the notion that an SU(2)L triplet scalar, characterised by a hypercharge Y = 0, could be the origin of the observed 95 GeV di-photon (γγ) excesses seen at ATLAS and CMS. By thoroughly examining its properties, particularly the neutral component, and considering a small mixing angle with the Standard Model Higgs boson, we uncover that this scalar naturally exhibits a substantial branching ratio to γγ. Additionally, we find that its Drell-Yan production via pp → W∗ → HH± adequately accounts for the observed excess. The second study examines how recent measurements of the W bosons’s mass by experiments such as ATLAS and CDF affect the theoretical predictions of the Two Higgs Doublet Model augmented with a Singlet Scalar (2HDM+S) model. It addresses how this model’s parameter space is further constrained by the inclusion of vector-like leptons, focusing on their impact on the muon g − 2 measurements. The third study involves exploring the potential discovery of the aforementioned scalar at future electron-positron colliders. Employing several methodologies, including the recoil mass method in e + e − collisions (e + e − → ZS, where Z → µ + µ − and S → b ¯ b), we leverage a Deep Neural Network to refine the differentiation between the Standard Model background and the targeted signal. The outcomes not only reinforce the potential for detecting the proposed scalar, but also enhance the scientific argument for the establishment of future electron-positron colliders like CEPC, FCC-ee or ILC. Together, these studies contribute valuable insights into the evolving landscape of particle physics.

Description

A thesis submitted in fulfillment of the requirements for the degree of Master of Science for the Institute for Collider Particle Physics, to the Faculty of Science, School of Physics, University of the Witwatersrand, Johannesburg, 2024.

Keywords

Absolute Luminosity For ATLAS, Collider Detector at Fermilab, Circular Electron Positron Collider, Compact Muon Solenoid, Large Electron Positron collider, Large Hadron Collider, Large Hadron Collider beauty, W bosons, Drell-Yan production, A Toroidal LHC ApparatuS, Higgs Triplet Model, Institute for Collider Particle Physics, UCTD

Citation

Mulaudzi, Anza-Tshilidzi. (2024). Exploring the 95 GeV Excess with Extended Scalar Models. [Master's dissertation, University of the Witwatersrand, Johannesburg]. WIReDSpace. https://hdl.handle.net/10539/45304

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