Beyond Standard Model At LHC

Prasad, Hemant (2022) Beyond Standard Model At LHC. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Hemant Prasad (17MS172)) 17MS172_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

The Standard Model of Particle Physics successfully explains the unification of Electromagnetic and weak interactions. Our best understanding of how particles and the three fundamental forces namely Strong, weak and Electromagnetic Forces interact with each other is encapsulated in this model. Under the Standard Model only the left hand neutrinos are placed in the SU(2) doublet with no corresponding mass terms. However SM fails to elucidate problems such as neutrinos masses, the hierarchy problem and the dark matter candidate. On July 4th 2012, the ATLAS and CMS collaboration announced the discovery of new particle of mass ~ 125Gev which resonates with the Standard Model Higgs boson. In this paper I study about the simplest extension of the Standard Model namely the U(1)B−L extension which explains some of the loopholes left by the SM, at the High luminosity Large Hadron Collider (HL-LHC). The extra scalar singlet mixes with the Standard Model Higgs giving rise to massive right handed neutrinos. This scalar, which we will call the Heavy Higgs Boson also interacts with the other Standard model particles, where the interaction is proportional to the Higgs mixing angle. I will specifically look for HeavyHiggs boson in pp → H2(→ ZZ → jjl⁺l⁻) and in pp → H₂(→ b¯b) channel. The huge QCD background in the latter case makes the channel very ineffective, the former one also have the ZZ continuum background however the leptonic sector of final states makes the channel much cleaner for any discovery prospect of HeavyHiggs at HL-LHC. The choice of ZZ channel over W⁺W⁻, t¯t and H2 → h1h1 is made because the former has neutrinos in the the final states leading to large missing transverse energy(MET) while the H₂ → h1h1 will have huge QCD background as the SM higgs would decay to b¯bb¯b final states. The events were generated using Monte Carlo simulator Madgraph5_@aMCNLO [11] and Pythia8 [15] and the detector simulation was done using DELPHES, then the .root files were analysed using madanalysis5[23].

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