An Automated NLO Framework in Sherpa

Abstract

There has recently been a strong drive towards next-to-leading order (NLO) accuracy in Monte Carlo event generators. This thesis is concerned with the implementation of a framework for NLO calculations within the matrix element generator AMEGIC++, which forms part of the Monte Carlo event generator Sherpa. An interface is presented for the connection of one-loop matrix elements to Sherpa, conforming with the Binoth Les Houches Accord. Automated Catani-Seymour dipole subtraction is presented for the cases of QCD corrections for processes involving massive final state particles, and the supersymmetric partners of quarks and gluons, namely squarks and gluinos. Similar dipole subtraction techniques are also applied to the case of
photonic corrections. An automated implementation of on-shell subtraction, relevant for separating real-emission NLO corrections from leading order production and decay processes, is also presented. With the completion of this work, the event generator Sherpa, when interfaced to
suitable one-loop code, is equipped to calculate all necessary components of QCD and electroweak NLO calculations.