Effective field theories for quantum chromo- and electrodynamics

TL;DR

This dissertation develops and applies effective field theories across different regimes of quantum chromodynamics and electrodynamics, enhancing precision in particle physics calculations and understanding hadronic interactions.

Contribution

It introduces new EFT frameworks for perturbative QCD, hadronic scattering, and electron-laser interactions, advancing theoretical tools and computational accuracy.

Findings

Proved universality of soft radiation in QCD using SCET.

Achieved NNLL accuracy for QCD processes at colliders.

Provided insights into the structure of the exotic hadron X(3872).

Abstract

In this dissertation, I introduce the principles and methods of effective field theory and describe my work in three EFTs: First, in the perturbative QCD region, I use soft collinear effective theory (SCET) to prove that strong interaction soft radiation is universal and to increase the QCD accuracy to next-to-next-tonext- to leading logarithm order for new particle searches in hadron colliders. I also compute a new class of non-perturbative, large logarithmic enhancement arising near the elastic limits of deep inelastic scattering and Drell-Yan processes. Second, in the QCD confinement region, I use heavy hadron chiral perturbation theory to study near-threshold enhancements in the scattering of $D$ and $\pi$ mesons near the threshold for the excited $D$-meson state, $D^*$, as well as in the scattering of $D$ and $D^*$ mesons near the threshold for the exotic hadron X(3872). This work provides a clear picture of the hadronic molecule X(3872) and more profound understanding of the nuclear force between hadrons. Finally, inspired by SCET, I construct a new electron-laser effective field theory to describe highly-relativistic electrons traveling in strong laser fields, extract the universal distribution of electrons in strong electromagnetic backgrounds and its evolution in energy from the separated momentum scales of emitted photons and classical radiation, and predict the rate of wide angle photon emission. I conclude with limitations of EFT methods and some perspectives on what new work may be achieved with these EFTs.