Tracker Readout Development for the CMS Upgrade and a Search for Light Higgs Bosons from SUSY Decay Cascades

This thesis focuses on two areas of the CMS experiment at the Large Hadron Collider (LHC): the upgrade work for the CMS detector at the HighLuminosity LHC (HL-LHC) and the Run 3 preparations for a Next-to-Minimal Supersymmetric Standard Model (NMSSM) search for light Higgs bosons. The HL-LHC will provide a higher instantaneous luminosity than the current LHC, resulting in a larger volume of data for physics analysis. However, this demands improvements in the triggering systems. In response, CMS is developing an innovative Level-1 (L1) hardware track trigger using data from the Outer Tracker. This thesis discusses the L1 Track Finder, which employs a pattern recognition algorithm implemented on Field Programmable Gate Arrays (FPGAs). The L1 Track Finder's primary objective is to reconstruct within 4 $\mu$s the trajectories of all charged particles detected within the Outer Tracker volume with transverse momenta greater than 2 GeV. The CMS upgrade work also includes testing of high-speed optical transceivers, which are crucial for efficient data transmission between the CMS backend systems. These transceivers are required to transmit data at a rate of 25 Gb/s with good signal quality. Performance studies of various optical transceivers are presented.Furthermore, the thesis discusses a search for light Higgs boson decays produced in SUSY decay cascades, in the context of the NMSSM. The analysis looks for events with little missing transverse momentum, where the light Higgs bosons decay to boosted $b$ quark pairs. The analysis builds upon a previously published study conducted using Run 2 data. The current work explores improvements for the upcoming Run 3 data from changing the double-$b$-tag discriminator and jet mass reconstruction to using the ParticleNet algorithm.