Speaker
Description
The method of regions provides not only a systematic approach to computing Feynman integrals, but also useful information of formulating an EFT. For example, the SCET$_{\rm I}$ Lagrangian describing massless wide-angle scattering elegantly combines collinear and ultrasoft modes. This is grounded in the empirical observation that each loop in a pertinent region is either hard, collinear to an external momentum, or ultrasoft. It is then natural to ask the following questions. Are all regions confined to the prescribed types observed in processes like wide-angle scattering? Can other types of regions emerge in other scenarios, e.g., heavy-to-light decay?
This talk aims to answer these questions by drawing from a recent research, arXiv: 2312.14012. For the on-shell expansion and the soft expansion of generic wide-angle scattering, an all-order result is validated: each region involves only the hard mode, collinear modes, and ultrasoft mode, with their interactions following certain structures. For the heavy-to-light decay processes, in contrast, more modes are involved as the loop number increases. We will also discuss high-energy scattering regions, exploring the possibility of the Glauber mode.