Monte Carlo Simulations of Heavy Particles for the Large Hadron Collider

As the Large Hadron Collider has switched on at CERN in Geneva, accurate predictions for complex hadronic processes are essential for the validation of theory and therefore the success of the machine. After motivating the requirement for a Monte Carlo event generator, the principles and Physics behind such a generator are laid out. Following this, the Monte Carlo tuning system Professor is used to give an assessment of the uncertainty from tuning Herwig++ and the results from this analysis used, along with a more accurate implementation of Higgs boson decays using the POWHEG method, to determine the error associated with searching for the Higgs boson with a jet substructure technique. Then, modifications to the shower to take into account the top quark width are presented along with radiation patterns from top quark production processes for up to two external gluons. A general algorithm is outlined for systematically including these corrections. Finally, as the LHC is ultimately a discovery machine, it is pertinent to provide Monte Carlo studies of new Physics. The colour sextet diquark model is looked at in the final chapter of this thesis, and the associated phenomenology studied.