The Large Hadron Collider (LHC) at CERN offers a promising opportunity to discover and characterize a putative new physics sector at the TeV energy scale. Due to the complexity of the experimental signatures, the direct search for new particles at this huge experimental facility is a real challenge, requiring a very clear understanding of the structure of hadron collisions. For this reason, in the last decade a tremendous effort has been devoted to improving the accuracy of theoretical scattering amplitudes. Very recently, a new milestone has been reached with the elaboration of algorithms capable of generating hard scattering amplitudes at next-to-leading-order accuracy. In this context, it is urgent to redefine strategies for new physics searches at the LHC which makes maximum use of state-of-the-art theoretical information.In this project, we consider more specifically the case of decay chains, which plays a very important role in the search for new physics. As a first objective, we propose to use our expertise in Monte Carlo techniques, spin physics and next-to-leading-order calculations to develop a generic decay algorithm designed specifically to retain all spin correlation effects at next-to-leading order accuracy in any decay chain in the Standard Model and beyond, and to implement this algorithm in the MadGraph framework. Secondly, we propose to develop a matrix-element-based likelihood method dedicated to experimental analyses involving decay chains and constructed to maximize the use of spin correlation effects. Finally, we propose to revisit, with the aid of these tools, specific searches for new physics at the LHC -in particular the search for a light Standard Model Higgs- and to assess the increase of significance that is gained with a careful treatment of higher-order radiation and spin correlation effects.