  I explore many aspects of jet substructure at the Large Hadron Collider,
ranging from theoretical techniques for jet calculations, to phenomenological
tools for better searches with jets, to software for implementing and comparing
such tools. I begin with an application of soft-collinear effective theory, an
effective theory of QCD applied to high-energy quarks and gluons. This material
is taken from Ref. 1, in which we demonstrate factorization and logarithmic
resummation for a certain class of observables in electron-positron collisions.
I then explore various phenomenological aspects of jet substructure in
simulated events. After observing numerous features of jets at hadron
colliders, I describe a method -- jet pruning -- for improving searches for
heavy particles that decay to one or more jets. This material is a greatly
expanded version of Ref. 2. Finally, I give an overview of the software tools
available for these kinds of studies, with a focus on SpartyJet, a package for
implementing and comparing jet-based analyses I have collaborated on. Several
detailed calculations and software examples are given in the appendices.
Sections with no new content are italic in the Table of Contents.
