Particle Theory Seminars

The particle theory seminars are organized by the Theory Group of the Laboratory for Particle Physics (LTP) at PSI.

The seminars are broadcast via zoom. Please contact Emanuele Bagnaschi to obtain the invitation link.

Contact: Emanuele Bagnaschi, emanuele.bagnaschi@psi.ch, WHGA/132, Tel. +41 56 310 36 60

The next seminar will take place on the 27th of April at 17:00 CEST.

Speaker: L. Vernazza (U. Torino)

Title: On the factorization of scattering processes near threshold at next-to-leading power

Abstract

Scattering processes near threshold develop large logarithms, that need to be resummed. Resummation is well understood for leading power logarithms; less is known concerning logarithms beyond leading power, and only recently people have started investigating systematically their structure. Ultimately, large logarithms in a scattering process near threshold arise due to the dynamical emergence of a soft scale: all the momentum goes into the observed final state, and there is little energy available for extra radiation. Understanding the structure of threshold logarithms is thus connected to the study of soft and collinear radiation in scattering amplitudes.

In my talk I will review the state of the art. I will start by discussing how soft and collinear radiation can be described, within a diagrammatic approach, in terms of universal jet and soft functions. I will then compare this framework with methods based on soft collinear effective field theory, which provide systematic tools to derive equivalent factorization theorems. I will discuss current problems within these approaches, which prevented so far a systematic resummation of large logarithms beyond leading power and leading logarithmic accuracy. I will conclude showing some numerical study, investigating the impact of resumming leading logarithms beyond leading power, for a variety of electroweak annihilation scattering processes.