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Abstract

New physics searches are one of the main aims of the CERN Large Hadron Collider. In most cases this entails the study of small expected signals versus huge backgrounds. Therefore, theoretically precise predictions for collider observables are crucial for the analysis of any possible new physics signature. A major improvement in this enterprise can be achieved through the calculation of the Next-to-leading order (NLO) QCD corrections for the process under scrutiny. Thus, in this thesis we focus on the quantitative and qualitative impact of the NLO effects on some important new physics signatures. To do so we have resorted to the new, fully automized package MadGolem, to which this thesis has made major contributions. The following important LHC search channels are examined herewith: i) scalar color-octet pair production; ii) associated squark--neutralino production; and iii) the pair production of squarks and gluinos. In all these cases we observe important QCD effects which lead to sizable quantum corrections (K~1.3-2) and strongly suppressed theoretical uncertainties, which deplete from O(100%) at leading-order down to O(30%) at NLO. Moreover, we have shown the NLO distributions to be in good agreement with those obtained via multi-jet merging. Finally, we have carried out a comprehensive study on the implications of the usual simplifying assumptions taken in the literature and in current tools, e.g. squark mass degeneracy.