Search for Higgs Boson Pair and Detector Upgrade on the CMS Experiment

The Standard Model of Particle Physics (SM) is a renormalizable quantum field theory that provides a comprehensive framework for describing phenomena occurring at subatomic scales. As a very important piece of the whole puzzle, the Brout-Engler-Higgs (BEH) mechanism serves as a solution for generating the masses of gauge bosons and elucidating the origins of fermion masses. This mechanism is rooted in the concept of spontaneous symmetry breaking. The key to understand the mechanism and the concepts better is to measure the higgs boson self-coupling and couplings with other fundamental particles. The only direct prob of the Higgs boson self-coupling at the LHC is the measurement of double or triple Higgs production processes, with interaction vertices characterized by couplings that are normalized by a kappa framework in experiments. The main challenge of the current experiments in searching Higgs boson pair (HH) and constrain the couplings is the small cross sections of the HH production processes. Physicists can enhance the physics performance from collider experiments in three different aspects: 1. Enhance the physics object tagging efficiency. 2. Enhance the event-level analysis strategy to increase the signal-to-background ratio. 3.Accumulate additional data and detector upgrades to enhance precision and acceptance The process of HH production associated with one vector boson (Z/W) is first time studied at CMS experiment with the full Run-2 (collected 2016-2018 at a center-of-mass energy of 13 TeV) data. The analysis includes all the vector boson decay channels and focuses on the HH decay to 4b final state. The leptonic decay of the vector boson allow us to constrain the HHZZ and HHWW coupling separately. This comprehensive analysis also incorporates the boosted topology, employing Boosted Decision Trees (BDTs) to establish a (HHH coupling modifier) enriched region and a (HHVV coupling modifier) enriched region. Optimization of the subsequent processes in parallel aims to enhance sensitivity