Searching for Long Lived Particles with ADAM (Auxiliary Detector above the ATLAS Muon Spectrometer)

• Author / Creator

  Lamichhane, Rishap

• The Large Hadron Collider (LHC) is the world’s largest particle accelerator, delivering proton-proton (p − p) collisions to various experiments, including ATLAS (A Toroidal
  LHC ApparatuS). The proposed Auxiliary Detector above the ATLAS Muon Spectrometer (ADAM) aims to expand the physics capabilities of ATLAS. Its primary objective is to detect
  the decay products of particles beyond the standard model (BSM), escaping detection from the ATLAS collisions.
  Long-lived particles (LLPs) represent a key aspect of BSM theories, and ADAM has the potential to extend ATLAS’s reach in this domain. One of these models of great interest is the hidden (dark) sector scalar model, which explains the origin of mass in the form of dark matter (DM). The theory suggests that DM particles acquire mass similar to electroweak symmetry breaking, forming a complete dark sector with additional scalar and vector bosons. The resulting scalar, known as the dark Higgs boson (ϕ), generally mixes with the Standard
  Model (SM) Higgs boson, displaying some SM-like characteristics. While physicists aim to detect such particles, many experiments, including ATLAS, are not inherently designed for this purpose. ADAM emerges as a cost-effective enhancement to the LHC infrastructure, extending the physics reach of the current ATLAS detector. Positioned above the ATLAS detector, ADAM transforms the upper cavern region into a fiducial volume of ∼ 12, 000 m^3 for detecting LLP decays. The evaluation of the spatial resolution performance using Silicon Photomultiplier readout from the proposed ADAM detector module is presented. We also present an overview of dark Higgs bosons (DHBs) produced in rare inclusive B meson, and exotic SM Higgs decays. Our analysis is performed under the operational scenario of High Luminosity - LHC run 4, anticipating an integrated luminosity of 715 fb−1 and centre-of-mass energy √s = 14 TeV. The analysis includes the reach of ADAM for the leptonic decays of lighter DHB to muons (ϕ → μ+μ−), with a requirement of at least three decays inside the fiducial volume, in the parameter space spanned by the mass of DHB (m_ϕ) and the mixing term sin^2 θ. Additionally, a comparison between the reach of ADAM and the existing experimental bounds for the DHB is also presented.

• Subjects / Keywords

  • Physics
  • Large Hadron Collider
  • Long-lived particles
  • ATLAS Muon Spectrometer

• Graduation date

  Fall 2024

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-twet-z108

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.