Search for Supersymmetry in proton-proton collisions at $\sqrt{s}$ = 13 TeV with at least one photon, jets and missing transverse momentum

The Standard Model (SM) explains three out of four fundamental forces except for gravity. One of the primary limitations of SM is a mass hierarchy problem, and the other is the inability to explain the presence of dark matter in the universe. The discovery of the higgs (H) boson in 2012 at the LHC, has also opened up new avenues for research and fueled further investigations into physics beyond the SM. Supersymmetry (SUSY) model can address discrepancies like the hierarchy problem by providing superpartners to SM particles with a different spin by half unit. It also offers a potential candidate for dark matter. This thesis presents a search for new physics in final states consisting of at least one photon, multiple jets, and large missing transverse momentum, using proton-proton collision events at a center-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 137fb$^{-1}$, recorded by the CMS experiment at the CERN LHC from 2016 to 2018. The events are divided into mutually exclusive bins characterized by the missing transverse momentum, the number of jets, the number of b-tagged jets, and jets consistent with the presence of hadronically decaying W, Z, or H bosons. The observed data are found to be consistent with the prediction from SM processes. The results are interpreted in the context of simplified models of pair production of supersymmetric particles via strong and electroweak interactions. Depending on the details of the signal models, gluinos and squarks of masses up to 2.35 and 1.43TeV, respectively, and electroweakinos of masses up to 1.23 TeV are excluded at 95% confidence level. These are the best mass limits to date on electroweakino production with photons in the final state.