In this dissertation, three different topics related to terascale physics are explored. First, a new method is suggested to match next-to-leading order (NLO) scattering matrix elements with parton showers. This method is based on the original approach which adds primary parton splittings in Born-level Feynman graphs in order to remove several types of infrared divergent subtractions from the NLO calculation. The original splitting functions are modified so that parton showering has a less severe effect on the jet structure of the generated events.

We also examine the Large Hadron Collider phenomenology of quantum black holes in models of TeV scale gravity. Based on a few minimal assumptions, such as the conservation of color charges, interesting signatures are identified that should be readily visible above the Standard Model background. The detailed phenomenology depends heavily on whether one requires a Lorentz invariant, low-energy effective field theory description of black hole processes.

Finally, in the calculation of cross sections in high energy collisions at NLO, one option is to perform all of the integrations, including the virtual loop integration, by Monte Carlo numerical integration. A new method is developed to perform the loop integration directly, without introducing Feynman parameters, after suitably deforming the integration contour. Our example is the N-photon scattering amplitude with a massless electron loop. Results for six photons and eight photons are reported.