This dissertation presents results from a search for physics beyond the Standard Model, using 19.39 pb-1 of data collected by the CMS detector at the Large Hadron Collider, during its 2012 operation at √ s=8 TeV. It focuses on models of supersymmetry that lead to final states with multiple jets, especially those from b-quark decay, and a large amount of missing transverse momentum. The amounts of background from top-quark, W+jets, Z → nu[special character omitted], and multi-jet production are determined from data-driven techniques. In particular, this includes a novel estimation of the ETmiss spectrum from semi-leptonic tt¯ decay, which takes advantage of the precise knowledge of the W boson polarization. Predicted yields are consistent with simulated Standard Model processes and the observed data. Since no evidence of new physics is observed, limits are placed on the rate of gluino pair production to a final state with four b-quarks and two neutralinos. This process is excluded at 95% CL for a gluino with mass 1225 GeV and a neutralino with mass up to 350 GeV.