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In this thesis I study the infrared limits of QCD beyond leading power by developing effective quantum field theory techniques. I introduce the motivations for studying this subject both as a tool to deepen our understanding of the infrared…
Soft-collinear effective theory (SCET) has become a standard tool to study the factorization of short- and long-distance effects in processes involving low-energetic (soft) particles and high-energetic/low-virtuality (collinear) modes. In…
We study the first power correction to the heavy electron form factor in QED and show that it factorizes as a derivative operator. We discuss the result in QED with no light fermions, where the first power correction can be written…
One-loop matching corrections are calculated for Soft-Collinear Effective Theory (SCET) operators relevant to the analysis of heavy-to-light meson form factors at large recoil. The numerical impact of radiative corrections on form factor…
Applying the dispersion approach we compute perturbative QCD corrections to the power suppressed soft contribution of $B \to \gamma \ell \nu$ at leading twist. QCD factorization for the $B \to \gamma^{\ast}$ form factors is demonstrated…
The accurate calculation of weak heavy-to-light form factors is crucial for the determination of CKM matrix elements from experimental data on B decays. In SCET, the soft-collinear effective theory, these form factors can, in the heavy…
We report on a first study of 4-jet production in a high energy factorization (HEF) framework \cite{Kutak:2016mik,Kutak:2016ukc}. We include and discuss contributions from both single-parton scattering (SPS) and double-parton scattering…
Factorization, in the sense defined for inclusive hard scattering, is discussed for diffractive hard scattering. A factorization theorem similar to its inclusive counterpart is presented for diffractive DIS. For hadron-hadron diffractive…
Soft Collinear Effective Theory (SCET) is an effective field theory of Quantum Chromodynamics (QCD) for processes where there are energetic, nearly lightlike degrees of freedom interacting with one another via soft radiation. SCET has found…
Jet broadening is an event-shape variable probing the transverse momenta of particles inside jets. It has been measured precisely in e+e- annihilations and is used to extract the strong coupling constant. The factorization of the associated…
Jet substructure has emerged as a critical tool for LHC searches, but studies so far have relied heavily on shower Monte Carlo simulations, which formally approximate QCD at leading-log level. We demonstrate that systematic higher-order QCD…
A persistent and fascinating problem at the high energy colliders are jets. Often trying to observe physics underlying the hard interactions at colliders requires experimental cuts in phase space, defining several jet or beam regions. QCD…
In this article, general properties of impact factors involved in jet-like QED processes are explored. In particular, a general link is established between their helicity properties and their order of magnitude as defined by jet-like…
We study the $N$-jettiness in the electroweak high-energy process for the final muon jet pairs, $e^- e^+ \rightarrow \mu^+ \ \mathrm{jet} + \mu^- \mathrm{jet}$. Compared to QCD, the main difference is that there exist additional gauge…
High-energy factorization in QCD is investigated beyond leading order and its relationship to the factorization theorem of mass singularities is established to any collinear accuracy. Flavour non-singlet observables are shown to be regular…
From a detailed analysis of cone-jet cross sections in effective field theory, we obtain novel factorization theorems which separate the physics associated with different energy scales present in such processes. The relevant low-energy…
We propose a factorization formula for the cross section for forward dijet production in dilute-dense collisions. The new formula is applicable for an arbitrary value of the momentum imbalance of the two jets, $k_t$. It unifies the…
Soft-collinear effective theory (SCET) is used to demonstrate factorization for event shape distributions in the two-jet region. The leading nonperturbative power corrections to these distributions can be characterized as shape functions…
We derive the QCD$\times$QED factorization theorem governing the leptonic decay $B^-\to\mu^-\bar\nu_\mu(\gamma)$ at all orders in $\alpha_s$ and $\alpha$. Electromagnetic corrections to this decay probe multiple scales, which we disentangle…
In this thesis, we discuss and investigate the use of Soft-Collinear Effective Theory (SCET) for high precision calculations. In the first part of the work, we present an extraction of the strong coupling, $\alpha_s(m_Z)$ and the leading…