U(2) Is Right for Leptons and Left for Quarks.

We posit that the distinct patterns observed in fermion masses and mixings are due to a minimally broken U(2)_{q+e} flavor symmetry acting on left-handed quarks and right-handed charged leptons, giving rise to an accidental U(2)^{5} symmetry at the renormalizable level without imposing selection rules on the Weinberg operator. We show that the symmetry can be consistently gauged by explicit examples and comment on realizations in SU(5) unification. Via a model-independent analysis of a standard model viewed as an effective field theory, we find that selection rules due to U(2)_{q+e} enhance the importance of charged lepton flavor violation as a probe, where significant experimental progress is expected in the near future.

A proof of concept for matchete: an automated tool for matching effective theories.

Studying the impact of new-physics models on low-energy observables necessitates matching to effective field theories at the relevant mass thresholds. We introduce the first public version of Matchete, a computer tool for matching weakly-coupled models at one-loop order. It uses functional methods to directly compute all matching contributions in a manifestly gauge-covariant manner, while simplification methods eliminate redundant operators from the output. We sketch the workings of the program and provide examples of how to match simple Standard Model extensions. The package, documentation, and example notebooks are publicly available at https://gitlab.com/matchete/matchete.

Introducing RGBeta: a Mathematica package for the evaluation of renormalization group ß -functions.

In completely generic four-dimensional gauge-Yukawa theories, the renormalization group ß -functions are known to the 3-2-2 loop order in gauge, Yukawa, and quartic couplings, respectively. It does, however, remain difficult to apply these results to realistic models without the use of dedicated computer tools. We describe a procedure for extracting ß -functions using the general results and introduce RGBeta, a dedicated Mathematica package for extracting the MS ¯ ß -functions in broad classes of models. The package and example notebooks are available from the GitHub repository.

Gauge Coupling ß Functions to Four-Loop Order in the Standard Model.

We compute the ß functions of the three standard model gauge couplings to four-loop order in the modified minimal subtraction scheme. At this order a proper definition of γ_{5} in D=4-2ε space-time dimensions is required; however, in our calculation we determine the γ_{5}-dependent terms by exploiting relations with ß function coefficients at lower loop orders.