Soft Gluons and Non-global Observables Mike Seymour – University of Manchester / CERN TH on behalf of Rene Angeles Martinez, Matthew De Angelis, Jeffrey R. Forshaw, Simon Plätzer, Michael H. Seymour based on JHEP 05 (2018) 044 (arxiv:1802.08531) Soft gluon evolution
• In particular, how does soft gluon emission affect subsequent soft gluon evolution? Soft Gluons and Non-global Observables
• Soft gluon emission evolution algorithm • An IR-finite reformulation • The ordering variable • Colour flow basis • (Towards) an exact numerical implementation • (“amplitude-level parton shower”) et al [14], as well as Weigert and Caron-Huot [7, 11, 30]. In Appendix B we make the can- cellation of infrared divergences explicit for observables that are inclusive below a resolution scale, and in Appendix C we explicitly calculate contributions in a fixed-order expansion. Finally, Appendix D sets up the machinery to deal with the fact that most colour bases are not orthogonal (see [31] for a notable exception).
2Thegeneralalgorithm
Our starting point is the cross section for emitting n soft gluons. At this stage we will assume that it is ok to order successive emissions in energy. This assumption is ok for processes that are insensitive to Coulomb gluon exchanges but appears not to be valid otherwise [29, 32]. We have that