Exploring the 95 GeV Excess with Extended Scalar Models

dc.contributor.authorMulaudzi, Anza-Tshilidzi
dc.contributor.supervisorMellado, Bruce
dc.contributor.supervisorKumar, Mukesh
dc.date.accessioned2025-07-01T11:05:07Z
dc.date.issued2024-10
dc.descriptionA 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.
dc.description.abstractThis 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.
dc.description.sponsorshipSA-CERN
dc.description.submitterMMM2025
dc.facultyFaculty of Science
dc.identifier0000-0002-7592-8634
dc.identifier.citationMulaudzi, 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
dc.identifier.urihttps://hdl.handle.net/10539/45304
dc.language.isoen
dc.publisherUniversity of the Witwatersrand, Johannesburg
dc.rights©2024 University of the Witwatersrand, Johannesburg. All rights reserved. The copyright in this work vests in the University of the Witwatersrand, Johannesburg. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of University of the Witwatersrand, Johannesburg.
dc.rights.holderUniversity of the Witwatersrand, Johannesburg
dc.schoolSchool of Physics
dc.subjectAbsolute Luminosity For ATLAS
dc.subjectCollider Detector at Fermilab
dc.subjectCircular Electron Positron Collider
dc.subjectCompact Muon Solenoid
dc.subjectLarge Electron Positron collider
dc.subjectLarge Hadron Collider
dc.subjectLarge Hadron Collider beauty
dc.subjectW bosons
dc.subjectDrell-Yan production
dc.subjectA Toroidal LHC ApparatuS
dc.subjectHiggs Triplet Model
dc.subjectInstitute for Collider Particle Physics
dc.subjectUCTD
dc.subject.primarysdgSDG-9: Industry, innovation and infrastructure
dc.subject.secondarysdgSDG-4: Quality education
dc.titleExploring the 95 GeV Excess with Extended Scalar Models
dc.typeDissertation

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