| Thesis | |
| Report number | CERN-THESIS-2024-307 |
| Title | Searching for Beyond the Standard Model particles decaying to muon pairs with SND@LHC |
| Author(s) | Santos, Henrique (U. Lisbon (main)) |
| Publication | 2024 - 78. |
| Thesis note | Master : Lisbon, CENTRA : 2024 |
| Thesis supervisor(s) | Leonardo, Nuno ; Vilela, Cristovão |
| Note | Presented 28 Nov 2024 |
| Subject category | Detectors and Experimental Techniques |
| Accelerator/Facility, Experiment | CERN LHC ; SND@LHC |
| Abstract | Although the Standard Model (SM) is a very successful theory, it is not able to explain some of the outstanding problems of modern physics. For addressing these shortcomings, an extension of the SM using Beyond the Standard Model (BSM) physics is required. The Scattering and Neutrino Detector at the Large Hadron Collider (SND@LHC) is a compact and stand-alone experiment recently installed at the LHC designed for the observation and measurement of collider neutrinos. In this thesis, we conduct the first search for Feebly Interacting Particle (FIP) at SND@LHC. This analysis is signature driven, focusing on generic FIP decays to dimuons more than the specific nature of the decaying particle. As our benchmark model, we chose the Dark Higgs, a scalar which interacts with SM particles through mixing with the SM Higgs. This FIP was simulated using the Forward Experiment Sensitivity Estimator (FORESEE) tool with a mass of 251.2M eV and decay vertex in the detector target. Through the use of both Monte-Carlo background samples and collision data samples, several signal selection criteria were devised, culminating in an expected neutrino background of <0.2 events and a muon background estimation in the signal region of 0.43±0.43 over 200fb^{-1}, corresponding to a 7 event background-only exclusion at 5σ. Simultaneously, this selection retains 13% of signal selection efficiency. Combining these values, we could expect background-only exclusion from, on average, 54 Dark Higgs decays on the target subsystem. Additionally, DH mixing angles above 10^{-3} are expected to be excluded for DH in our mass range. |
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Email contact: henrique.sousa.santos@tecnico.ulisboa.pt
Record created 2025-01-16, last modified 2025-01-22
