This thesis presents a search for direct and gluino-mediated production of supersymmetric scalar top-quark pairs in the all-hadronic final state using top tagging. The result of search is based on a 13 TeV proton-proton sample collected with the CMS detector at the LHC, corresponding to an integrated luminosity of $36 fb^{-1}$. The results of the search are interpreted in several Simplified Models (SMS).

A search is presented for physics beyond the standard model based on

events with significant missing transverse energy, at least three

jets, and at least one identified bottom-quark jet. The study is based on a sample of

19 fb-1 collected at 8 TeV with the CMS detector at the Large Hadron Collider in 2012.

The background from standard model processes is evaluated

using data control samples, and a global likelihood fit is

performed. The data are found to be consistent with standard model processes,

and the results are interpreted in the context of simplified models (SMS).

Upper limits on the production cross sections of the T1bbbb and T1tttt

SMS new physics scenarios are determined. Gluino masses up to 1170 GeV are excluded

for the T1bbbb scenario and up to 1020 GeV for the T1tttt scenario,

at 95% confidence level.