Multiparton scattering amplitudes with heavy quarks: calculational techniques and applications to diffractive processes

Abstract

In this thesis we demonstrate the use of twistor inspired methods in the calculation of gauge theory amplitudes. First, we describe how MHV rules and the BCF recursion relations can be used in QED. Then we apply BGF recursion to the problem of amplitudes with massive fermions in QCD, using the process gg → bbg as an illustration. Central exclusive production is a promising method of revealing new physics at the LHC. Observing Higgs production in this scheme will be hampered by dijet backgrounds. At leading order this background is strongly suppressed by a J(_z) = 0 selection rule. However, at higher orders there is no suppression and so it is important to calculate the contribution to the cross section of these terms. Among the necessary theoretical inputs to this calculation are the loop corrections to gg →bbg and the amplitude describing the emission of an extra gluon in the final state, gg → bbg. We provide analytic formulae for both these ingredients, keeping the full spin and colour information as is required.