Search for supersymmetry in $\sqrt{s}$ = 13 TeV p-p collisions using the $\alpha_T$ variable with the CMS detector

The search for BSM physics is one of the primary objectives of the LHC. This thesis describes the $\alpha_T$ search for supersymmetry using a dataset of 12.9 fb$^{−1}$ collected during the 2016 proton-proton runs by the CMS detector. The search uses a final state containing significant hadronic activity in the form of jets, missing energy, and no leptons or photons. Dedicated dimensionless variables ensure that backgrounds with fake missing energy are mitigated. A detailed description is given of the selections used to mitigate backgrounds while maintaining acceptance to a wide range of signal models and of the techniques used to ensure a robust determination of the residual backgrounds and systematic uncertainties. No evidence for BSM physics is observed and simplified models are therefore used to interpret the results of the search. Stringent new limits are placed on a range of supersymmetric topologies and a procedure to allow the search to be re-interpreted for any BSM physics model is presented. Additionally, the upgrade of the Level-1 trigger jet and energy sum algorithm is studied. The upgraded trigger hardware is exploited to ensure effective performance in conditions exceeding the design specification of the LHC.